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Creeping Alfalfas
CREEPING ALFALFAS
D. H.
Heinrichs
Canada Department of Agriculture, Swift Current, Saskatchewan, Canada
I. Introduction ................................................ 11. Types of Root Systems in Alfalfa .............................. A. Rhizomatous Plants ...................................... B. Creeping-Rooted Plants ................................... 111. Physiological Considerations ................................... IV. Breeding for the Creeping-Root Character ....................... V. Genetics of the Creeping-Root Character ....................... VI. Association of the Creeping-Root Character with Other Plant Characters VII. Agricultural Performance of Spreading Alfalfas ................... VIII. The Future of Spreading Alfalfas ............................... References ..................................................
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I. Introduction
The existence of creeping alfalfas has been known at least as far back as the turn of the century. During his trips to Russia and Siberia as Agricultural Explorer for the United States Department of Agriculture (1897-1898, 1906, 1908-1909), N. E. Hansen observed creeping plants in varieties of wild growing, yellow-flowered alfalfa ( Medicago falcata L. ) at several locations. In his account, Hansen (1909) reports that Klingen, a Russian agronomist, found as many as one hundred branches on one plant of M . falcata. He states, “the plants of the variety grow upright on the steppe but if pastured closely, they creep and only the ends are erect.” Hansen mentions that the native M . falcata strains in the Volga region of eastern European Russia endure pasturing, whereas introduced strains of Medicago sativa L. do not. In a later publication (Hansen, 1927), he says this about M . falcata he observed in Orenburg province: “Some people are interested in this variety because of its habit of sprouting from the roots at some distance from the original crown.” Oakley and Garver ( 1913, 1917), Oliver ( 1913), Garver (1922), and Southworth (1921) studied various root systems of alfalfa. The general conclusions arrived at by these workers are perhaps best summarized by Southworth, who states: “The hardiness of alfalfa depends very largely 317
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on its root system. Plants possessing a branched-root system are much better able to withstand heaving than those having only a single taproot, no matter how great its length may be. Those plants which have the power to produce rooting underground stems are able to renovate themselves, and after the death of the main rootstock are capable of keeping up a separate existence quite independent of the parent rootstock. When alfalfa has the habit of spreading by means of root proliferation, we have a form of spreading and multiplying in a vegetative manner which promises to give the plant greater powers of resistance to cold and also greater powers of recuperation from injury than is possessed by even true rhizomes, and we venture to hope that these properties will render it possible to grow good crops in adverse climatic conditions under which it would be quite impossible to raise common alfalfa.” This statement suggests many possibilities of expansion for the alfalfa crop and has many agricultural implications. Small samples of M . falcata were distributed quite widely to farmers during the early 1920’s from Brookings, South Dakota, where Dr. N. E. Hansen was stationed. Although a few plantings from the original seed distribution were successful, very little of agricultural significance resulted from them, probably because of very low seed yields or lack of follow-up by plant breeders and agronomists. Nevertheless, the foundation for extending alfalfa use into drought-ridden areas had been laid, and a number of plant breeders, as well as farmers, retained an interest in the yellow-flowered alfalfas. After the widespread drought of the 1930’s in the Northern Great Plains region of North America, it was noted that certain M . falcatn plantings had come through the dry period with very little reduction in stand. Four plantings were known in Canada and an undetermined number in the United States. A very successful planting was that of Claude Foster at Coal Springs, South Dakota. The alfalfa in this planting exhibited the creeping-root character to a considerable degree. Very little use under cultivation has been made of the native alfalfas of Russian and Siberian origin within the U.S.S.R. itself. This can be gathered from a statement by Komarov (1945): “Nearly all the wild lucernes within the limits of the U.S.S.R. have up to the present been scarcely tried in cultivation. Their nutritive qualities and the drought resistance of some of the species led us to believe that upon their introduction into cultivation, these species will play a not insignificant role in the problem of reclamation of the desert areas and wastelands of the U.S.S.R.” That the creeping-root character was manifest in some of these species is indicated by certain root descriptions given in the book. Renewed interest in creeping types of alfalfa paralleled the interest
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in regrassing and soil conservation in North America ( Aamodt, 1952). It was the apparent need for a persistent legume that started a number of breeding programs in the United States and Canada which undertook to develop more drought-resistant and winter-hardy varieties. Alfalfa breeders at several research institutions began to hybridize plants of M . falcuta and M.sutiva extensively in their breeding programs and discovered spreading plants within the F1 and later generations. Four varieties possessing the spreading habit to a certain degree have been developed as a result of breeding: RHIZOMA released in 1948 (Nilan, 1951), RAMBLER released in 1955 ( Heinrichs and Bolton, 1958), TETON released in 1958 ( Adams and Semeniuk, 1958), and NOMAD released in 1951 (Burlingham & Sons). The breeding program at the Experimental Farm, Swift Current, Saskatchewan, started by Dr. S. E. Clarke (Heinrichs, 1954) did more to stimulate intercst in development of creeping-rooted types of alfalfa than any other recent program. Breeding stock of creeping alfalfa was distributed freely to research institutions in many parts of the world and is being widely used in breeding programs aiming to develop creepingrooted strains. Until very recently, creeping alfalfas were considered to be useful mainly for pastures ( Aamodt, 1952; Heinrichs, 1954; Graumann, 1955, 1958). However, this does not mean that the creeping-root character, if present in high-yielding, quick-recovering hay types, might not add to their usefulness. In recent breeding studies involving creepers of northern origin and high-yielding southern varieties, it has been shown that the creeping-root character is not very closely linked with winter dormancy (Dudley and Hanson, 1961; Edye et al., 1961; Daday, 1962). The character therefore promises to have a much wider application in broadening the usefulness of alfalfa than had been previously believed to be possible. II. Types of Root Systems in Alfalfa
Most of the cultivated alfalfa varieties have a tap-root system. This type of root system is characteristic of varieties originating from M . sativa L. A tap-rooted plant has a rather narrow protruding crown, the tap root penetrating vertically into the ground with branch roots arising at intervals from it. Such plants are unable to spread sideways except to a limited degree by crown expansion as the plant ages. The branch-rooted alfalfa varieties and those with a proportion of both branch and tap roots are of more recent origin. The varieties used in North America differ widely in the extent to which their primary roots are branching (Smith, 1951). These types have variegated flowers and
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are considered to have originated from natural or artificial crosses between M . satiua and M . falcata; they are often designated as M . media Pers. The majority of such varieties have been developed in northern areas where winters are cold or in areas which are cold because of high elevation. The variety LADAK, a typical variegated variety, with a branched-root system, came from a natural population in the province of Ladakh, India. A branch-rooted plant differs from a tap-rooted plant in that a number of main primary roots arise from the crown instead of only one, and the crown is inclined to be wider. Such plants are able to develop adventitious shoots from the roots. This was demonstrated by Smith (1950), who found that adventitious shoots developed on root segments of LADAK and an M . falcata strain, but not on plants of GRIMM, RANGER, COSSACK, and MONTANA COMMON. Murray (1955) found that adventitious shoots developed also on plants of LADAK, but to a lesser degree than on creeping-rooted plants. Branch-rooted plants are able to withstand heaving during unfavorable winters better than tap-rooted plants. This has been found to be the case in the variety NARRAGANSETT, which is described as having a much-branched root system (Odland and Skogley, 1953). Although the branched-root system in alfalfa can be considered to result in a slight tendency for the plant to spread horizontally, the spread is restricted to the above-surface crown. There are two types of root systems in alfalfa which enable the plant to spread horizontally. These are generally referred to as rhizomatous and creeping-rooted. In the first instance, the spread is attributed to lateral expansion of the low-set crown by short horizontal stems, and in the second the spread is brought about by horizontal roots from which shoots may arise at irregular intervals, Graumann (1955,1958) explains the difference between rhizomatous and creeping-rooted type of spread quite adequately. He also makes it clear that any one strain or variety may have in it a variety of crown and root types. The difference between the two types of spread often is not too clearly demarcated or too well understood, and therefore each will be dealt with under a separate heading. Four types of plants representing different degrees of spread and different root systems are illustrated in Fig. 1. The plants shown in this photograph were excavated in October, 1962, from.an old stand of M . falcata growing on the Experimental Farm, Swift Current, Saskatchewan. This strain is one of N. E. Hansen’s introductions from Siberia, probably the strain known as Semipalatinsk. These plants although differing greatly from one another in ability to spread, have one characteristic in common, and that is the low crown which is located mostly below the soil surface. The low crown, perhaps, is the characteristic in M. falcata
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which differentiates it from M. sutivu to a greater extent than the roots themselves. Excellent descriptions and photographs of different crown and root systems and their relationships to types of alfalfa have been
FIG. 1. Plants of M . falcata, probably of the strain Semipalatinsk, excavated in September, 1962, in a 25-year-old field of crested wheatgrass at the Experimetal Farm, Swift Current, Saskatchewan. The alfalfa was an experimental planting seeded the same time as the grass. The photograph shows the deep-set crown of all plants and the different root systems, Left to right: tap root, branch root, rhizomatous root, creeping root.
presented by Garver ( 1922). Garver’s descriptions parallel closely what is said about roots in this article, suggesting that in the study of various alfalfa root systems little progress has been made during the last forty years. A. RHIZOMATOUSPLANTS The rhizomatous type of spread in alfalfa has been described in some detail by Oliver ( 1913) and more recently by Graumann (1958). The spreading of this type of plant is assumed to arise from stems of rootlike appearance which are initiated from the original primary root axis. These rhizomes extend laterally for varying distances, eventually root over part of their length, and emerge from the soil as vegetative stems. Dr.
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G. G. Moe of the University of British Columbia developed the variety which typifies this type of crown and roots (Nilan, 1951). Smith ( 1955) investigated the underground crown branches ( rhizomes) of a number of varieties. Of the varieties tested, RHIZOMA had the most rhizomes and ARIZONA COMMON the least. There seemed to be a direct relationship between the quantity of rhizomes and the amount of hl. falcatu which figured in the parentage of the varieties. Hanson et al. (1960) express the same thought in Agricultural Handbook No. 177. NOMAD is another new variety with extensive rhizome development ( Aamodt, 1952). It has been observed by Heinrichs (1954) that RHIZOMA and NOMAD do not spread to any extent in the arid climate of the prairie region of Canada. He attributed the lack of rhizomatic spread to inadequate soil nioisture conditions at the surface. Hanson et al. (1960) make the observation that RHIZOMA and NOMAD do not show much tendency to spread in many regions of the United States. The writer is of the opinion that rhizomatic plants will tend to spread quite strongly if climatic conditions are humid and the surface soil is moist for prolonged periods, particularly in the fall. Rooting may occur not only from underground stems, but also from prostrate stems lying on the soil surface. If animals graze and trample rhizomatous plants during such moist periods, the plants will tend to spread even more rapidly than when left ungrazed because the stems may grow more prostrate and thus get tramped into the ground where they can root from the nodes. Rhizomatous plants generally expand in crown width, and the top growth from them is very dense per unit area (Fig. 1 ) . RHIZOMA
B. CREEPINGROOTED PLANTS Truly creeping-rooted plants were described and illustrated by Oakley and Garver (1913), Oakley (1917), Southworth ( 1921), and Garver ( 1922). Recent descriptions and illustrations of this type were presented by Heinrichs ( 1954), Murray (1955), and Heinrichs and Bolton ( 1958). Actually, when creeping-rooted plants showed up in breeding populations resulting from intercrosses between M . falcuta and plants of the varieties LADAK and RHIZOMA, it seemed as though a new discovery had been made. This was the impression because certain hybrids were expressing the spreading habit to a much greater extent than any M . falcata parent. This accentuated spread in hybrid forms appeared to be due to complementary gene effects rather than to hybrid vigor (Heinrichs, 1954). A typical creeping root of a hybrid type is shown in Fig. 2 and of growing plants in Fig. 3. The creeping rootstocks are generally found to be 4 to 8 inches below the surface of the ground. They send up
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shoots at intervals, each of which is capable of becoming an independent plant. Some plants are dense creepers, others sparse; that is, certain plants produce more shoots per unit area than others. The sparse type of creeper may be the more desirable type for dryland pastures than
FIG. 2. A typical creeping-rooted plant which shows M . satiua as well as M . fakutu characteristics. The creeping-root development is more distinct than is the case in plant 4 in Fig. 1, which tends to display a combination of rhizomatous and creeping-root development. The pedigree of this plant in terms of varieties is: LADAK x (LADAK X M . f&ai%).
the dense type because in a mixed stand the alfalfa and grass plants will tend to form an interspersed association. Also, there will be less tendency for the stand to become too thick during favorable moisture years, with subsequent lower productive capacity in dry years. Murray (1957) studied the ontogeny of adventitious stems on roots
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of creeping-rooted alfalfa. She found that the horizontal roots are anatomically true root structures resembling the primary roots. They produce adventitious stems on a much greater range of roots than branch roots. Murray states: “At successive intervals of time in the ontogeny of adventitious stems, there are certain changes which occur within the root during two intimately associated phases of activity. One phase is the initiation and development, at the periphery of the root, of a primordial dome. The other is the differentiation of the subjacent secondary phloem parenchyma cells to form a meristematic zone in which vascular
FIG. 3. Early spring growth showing the spread of strongly creeping-rooted plants, 5 years old. The planting in this nursery originally was 6 feet each way. The plots contained 4 plants of a clonal line, Note that the creeping-rooted plants are encroaching on the noncreepers.
tissues differentiate and connect the peripheral primordia with the cambium of the root.” She further states that the inherent difference in creeping-rooted and noncreeping-rooted plants is in some way associated with the ability of the former to initiate stem primordia on all roots, whereas in the latter this ability is restricted to very few roots and perhaps is seldom brought into function. The writer observed, in the spring of 1962, when severe winter injury occurred in spaced populations, that some branch-rooted plants sent up new shoots from the roots located 4 to 6 inches underground when the main crown had been destroyed as a result of winter injury. Thus, it may be that in noncreeping plants, adventitious shoots are developed mainly under stress conditions.
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111. Physiologic01 Considerations
It is a fact that most of the spreading types of alfalfa presently being used as forage crops or for breeding purposes originated in northern areas where the winters are long and cold. It is natural, therefore, that most spreading alfalfas have long dormant periods in their growth cycles and slow regrowth characteristics. The spreading character as such, however, is not restricted to northern types. Oliver (1913) reports rhizome development in native varieties found in northern Africa. He states that the principal functions of the large rhizome may be the storage of water to tide the plants over the very hot and dry summers, because the rhizomes of these plants in northern Africa are evidently formed at the close of the growing season, which is during the winter months, but when brought to a colder climate they form during the autumn months. Aamodt (1952) mentions that wild forms of spreading alfalfas were found in Turkey by H. L. Westover in 1931. These alfalfas were growing in desertlike, denuded fields which the natives call “goat pastures.” Rhizomatous types were also found in Spain and Greece growing along roadsides, in fence rows, and in pastures among grasses. These observations suggest that drought resistance and ability to grow under competition and stress may be the common denominator, rather than cold resistance of the wild forms of spreading alfalfas. Plant breeders in subtropical and tropical climates may be well advised to consider using Mediterranean or Turkish wild alfalfa types in their programs aiming to develop persistent pasture types for their climatic conditions rather than those from northern regions. To the knowledge of the writer there is limited information from physiological studies on spreading alfalfas that relate the rhizomatous or creeping-root characteristic with any clearly defined physiological function. Ludwig (1960) used the technique of “growth analysis” to relate the main environmental factors on the early growth of a creepingrooted clonal Iine selected out of Canadian material. He found that number of plants with adventitious shoots was increased by short days, high light intensities, and high day and night temperatures. The number of adventitious shoots per plant was increased by the same environmental factors. Adventitious shoot production appeared to be directly associated with the growth rate of the roots and the top-to-root ratio, and indirectly with the net assimilation rate. Generally, those environmental factors which increased the net assimilation rate or decreased the top-to-root ratio, increased root growth and the production of ad-
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ventitious stems. Root segments removed from plants in each environmental treatment and placed in sand in the greenhouse all produced adventitious shoots. This indicates that the environment in which the plants had been growing had little effect on the potential of roots to form adventitious shoots. Since Ludwig’s study was done on a creeping-rooted clone of northern origin the root responses to environmental changes may be directly associated with this particular genotype, That creeping-rooted clones of different growth form may respond differently to environmental conditions in the formation of adventitious shoots, is indicated by results from a recent study by Ludwig (personal correspondence). He found that although in the majority of genotypes daylength had very little effect on the production of adventitious shoots, one clone produced many adventitious shoots in long days but scarcely any in short days, and another produced many shoots on the roots in short days, but scarcely any in long days. The initiation of adventitious shoots, Murray (1957) points out, is likely to involve an interrelationship of many factors. These could be physical ( size and number of primordia), physiological ( chemical stimulus for differentiation and growth and environmental responses), and genetic (an inherent characteristic of the plant). There is no doubt that more knowledge of the nongenetic mechanisms which influence adventitious stem formation would be very useful to the plant breeder in understanding hereditary factors and to the agronomist in forecasting where the creeping type might fit into a particular environment. Winter hardiness relationships among a number of varieties, three of which were of the spreading type, were reported by Heinrichs and Bolton (19%)) Heinrichs (1958, 1959)) and Heinrichs et aZ. (1960). It was quite obvious from the results that increased winter hardiness cannot be attributed to the spreading habit of growth alone. The character must be present in an inherently winter-hardy type. Thus, NOMAD, a spreading variety, was much less persistent in the Prairie Provinces of Canada than the nonspreading varieties VERNAL, GRIMM, and LADAK, which are commonly grown in the area. On the other hand, the creepingrooted variety RAMBLER, which possesses adequate winter hardiness, maintained a better stand than any other variety. This situation was also shown by Clark (1960). That creeping-rooted alfalfas may survive better than noncreepers of similar genotype was noted by Heinrichs (1954). He states: “In creeping-rooted plants, when the main crown was dead, numerous shoots appeared from creeping rootstocks at a considerable distance from the crown. It appeared that killing of the main crown actually stimulated development of aerial shoots from creeping root-
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stocks.” It can be reasoned, therefore, that heaving damage or severe overgrazing may similarly stimulate plants to spread. In Australia, Morley et al. (1957) investigated Canadian creepingrooted clones, locally adapted clones, and intercrosses between them for reaction to temperature and day length. They found that clones differed greatly in their reaction to these two environmental factors. The creeping-rooted clones from Canada were very low in winter production because of the winter dormancy characteristic. They state that although introduction of alfalfa breeding material from these northern regions is undoubtedly justified, the concomitant winter dormancy must be eliminated before derived strains can be unreservedly recommended for Australian conditions. In a recent physiological study, Daday (1962) showed that although RAMBLER required short days and low temperatures for best development of creeping roots, the F2 and F3 creeping derivatives from RAMBLER crossed with AFRICAN, HAIRY PERUVIAN, and HUNTER RIVER developed creeping roots satisfactorily when days were longer and temperatures higher. When considering the use of spreading alfalfas in any particular region, one dare not leave out consideration of the environment at their point of origin. The potential real usefulness of the creeping character may never be realized unless it is transferred by breeding to strains physiologically adapted to a specific environment. IV. Breeding for the Creeping-Root Character
Oakley and Carver (1913, 1917) reviewed the agronomic possibilities that lie in the development of new alfalfa strains by hybridizing forms of M. falcata and M . satiua. Superior drought resistance and winter hardiness were considered to be the main desirable characters of M . fulcuta, and they pointed to the role this species has already played in the formation of useful varieties as a result of natural crossing. GRIMMis mentioned as an outstanding example of such a variety. They also envisaged that by the use of the proliferating root character, high-yielding strains may be originated that will be especially resistant to severe climatic conditions and actually aggressive on soils of fairly loose texture. Breeding programs using the principle of combining characters of the two species into more useful varieties were almost at a standstill until after the Great Drought of the 1930’s in the Great Plains area of North America. In Canada such a breeding program was undertaken in 1938 at the Experimental Farm, Swift Current, Saskatchewan, and the aims were outlined by Heinrichs ( 1954). He states that the objective was to combine the winter-hardy and persistence qualities of M . fulcata
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with good seed-producing qualities of common varieties. The breeding procedure followed was based on determination of the combining ability of individual plants. It was the rediscovery of strongly creeping-rooted types in the hybrid populations that led to concerted efforts to develop a creeping-rooted variety adapted to conditions in the Canadian prairies. Principles of general and specific combining ability were used to evaluate creeping-rooted selections for transmission of this character along with other useful agronomic characters to their progenies. The breeding objective was finally reached in 1955 with the release of the variety RAMBLER ( Heinrichs and Bolton, 1958). Interest of alfalfa breeders of North America in creeping-rooted types of alfalfa was greatly stimulated at the Twelfth Alfalfa Improvement Conference held in Lethbridge, Alberta. At this conference a paper on the subject was presented by Heinrichs (1950) and field demonstrations of spreading plants were shown. Breeding stock of creeping-rooted alfalfa was sent out from the Experimental Farm, Swift Current, Saskatchewan, to a great many institutions in all parts of the world. In addition, the strains of M . falcata and M . falcata X M . sativa origin available at the South Dakota Agricultural Experiment Station, Brookings, South Dakota, were a good source of the creeping character. These could be traced back to N. E. Hansen’s alfalfa introductions from Europe and Asia. At the present time substantial breeding projects, aiming to develop suitable creeping-rooted strains for specific environments, are underway at the following institutions: United States of America Crops Research Division, U.S.D.A. and North Carolina State College, Raleigh, North Carolina. John W. Dudley. Department of Plant Breeding, Cornell University, Ithaca, New York. C. C. Lowe and R. E. Anderson. Nevada Agricultural Experiment Station, Reno, Nevada. H. L. Camahan. Crops Research Division, U.S.D.A. and University of Nebraska, Lincoln, Nebraska. W. R. Kehr. South Dakota Agricultural Experiment Station, Brookings, South Dakota. M. D. Rumbaugh. Kansas State University, Manhattan, Kansas. E. L. Sorenson. Canada Experimental Farm, C.D.A., Swift Current, Saskatchewan. D. H. Heinrichs. Research Station, C.D.A., Lethbridge, Alberta. M. R. Hanna. Genetics and Plant Breeding Research Institute, C.D.A., Ottawa, Ontario. H. A. McLennan. Chile Oficina Estudios Especiales, Casilla 2-P, Santiago. Avendano T. Raul and Ruco E. Osvaldo.
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Australia Division of Plant Industry, C.S.I.R.O., Canberra. H. Daday and F. H. W. Morley. Division of Tropical Pastures, C.S.I.R.O., Brisbane. E. H. Hutton and L. A. Edye New Zealand Crop Research Division, D.S.I.R., Christchurch. T. P. Palmer. Great Britain Welsh Plant Breeding Station, Aberystwyth, Wales. W. Ellis Davis. Denmark Forsogsgarden Hojbakkegard. Albertslund pr. Taastrup. H. J. Moller Nielsen.
Methods of breeding for the creeping-root character need to differ little from those used for other quantitatively inherited characters. Heinrichs (1954) states that determination of combining ability of individual plants appears to be a good method for evaluating the capacity to transmit creeping-rootedness to progenies. The best time to score for degree of creeping-root development was in the spring, one year after planting. Creeping-rootedness, however, did not express itself in all plants until two or even three years after planting at Swift Current, Saskatchewan. In a later study of similar material, Morley and Heinrichs (19so) found that general combining ability was more important than specific combining ability, and therefore they concluded that mass selection would be very efficient in breeding for creeping-root. Jones and Hanson (1959) crossed the varieties AFRICAN, BUFFALO, CALNEFDE, and nine North Carolina clones on three Canadian creepers, and in the F2 recovered creeping-rooted plants from crosses with each of the varieties. The North Carolina selections transmitted different amounts of creep to their progenies, indicating the association of complementary factors with the expression of creeping roots. They also observed that the inherent vigor of plants has a bearing on expression of the creeping growth habit. Australian alfalfa breeders are concerned with combining the creeping-root character from Canadian creepers with summer and winter growth habits of subtropical and tropical alfalfas. The writer spent 10 months in Australia during 1961 and was quite impressed with the progress being made at the Fs generation level. The Canadian creepers show creep development in Australia but lack growth vigor, and in Queensland they produce practically nothing. In the F3 generation extremely vigorous creepers were found, as Edye et uZ. (1961) and Daday ( 1962) have shown (Fig. 4). Edye et al. concluded that mass selection for creeping-rootedness in the third and later generations should be an efficient method of breeding. Daday found that the varieties HUNTER RIVER, HAIRY PERUVIAN, and AFRICAN in crosses with RAMBLER produced only 5 per cent creepers in F1 but an average of 41 per cent in the F3 generation resulting from intercrosses of F2 creepers. The range
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in creep between F3 lines was 0 to 81 per cent (Fig. 4).This compares quite favorably with plantings observed by Heinrichs (1954), who used the northern varieties LADAK and RHIZOMA in his breeding program. In a breeding program initiated at the U S . Regional Pasture Laboratory, University Park, Pennsylvania, Carnahan ( 1959) investigated
FIG. 4. An alfslfa breeding nursery at C.S.I.R.O., Canberra, Australia. The population is second and third generation material from crosses between Canadian creepers and African, DuPuits, and Hunter River selections. The stakes mark the creeping-rooted plants. The photograph was taken near the end of August (end of winter). Note the different degrees of winter dormancy.
methods of evaluating alfalfa for the creeping-root character. He found that creeping root expressed itself with the same expectation in nurseries oversown with timothy as in cultivated nurseries. The work involved in the oversown nurseries was less and, considering that the alfalfa will likely be grown in association with grass, such nurseries may be preferable for evaluating the alfalfa plants for creep development. When considering the breeding programs conducted at widely separated locations, there seems to be unanimity of opinion that fairly rapid progress is possible by following accepted breeding practices based on progeny performance. It also appears obvious that the creeping character must be transferred to varieties adapted to a particular climate before it can display its usefulness in improving persistence.
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V. Genetics of the Creeping-Root Character
The variation in type of spreading root systems and the overlapping that appears to occur between one type and another (Fig. 1 ) would tend to lead one to assume that the inheritance of this character might be complex. Heinrichs (1954) proceeded to breed for creeping root on the assumption that the character was a quantitative one. The data he obtained from combining ability tests of creeping-rooted selections seem to justify the assumption, and he concluded that the character appears to be a quantitative one with complementary factors playing a part. Morley and Heinrichs (1960) statistically examined the data obtained on the creeping-root character from a large population of alfalfa grown in experimental blocks at Swift Current, Saskatchewan. Their analysis showed that the estimate of Cov. (full sibs)-Cov. (half sibs) was 0.062, and of Cov. (half sibs) was 0.091, indicating that the genotypic variation was predominantly additive. In a study on estimates of variance in root proliferation in alfalfa, Adams (1959) found that the genotypic variance for extent of creep was mostly nonadditive and not highly heritable. In his analysis, however, Adams did not include the noncreeping fraction of the progenies, and, hence, the results give no information on the inheritance of creeping-root development versus no creep development. Further light on this apparent discrepancy was shed by a study by Heinrichs and Morley (1962). They found that when the data from the entire population were analyzed the genotypic variance was predominantly additive, but when only the creeping fraction was examined the genotypic variance was largely nonadditive. The conclusion drawn from this finding was that the creeping-root character versus tap- or branch-root character is quite highly heritable but the degree of spread is influenced strongly by nonadditive genotypic and environmental factors and perhaps by genes determining vigor of growth, as Jones and Hanson (1959) suggested. Daday (1962), working with a population of a somewhat different background, found considerably more of the variance to be due to nonadditive genetic effects than did Morley and Heinrichs ( 1960) and Heinrichs and Morley (1962). The heritabilities reported for the creeping-root character are quite good, varying from 20 per cent (Morley and Heinrichs, 1960) to 31 per cent (Heinrichs and Morley, 1962), calculated on the individual plot basis. Low heritability, reported by Adams (lQSQ),was substantiated by Heinrichs and Morley (l%2), but applied o d y to degree or extent of spread. Based on the fact that the data from a simple two-way classification into creeping and noncreeping plants gave approximately the
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same heritability estimates as those from five scores (1, 2, and 3 representing degrees of creep, and 4 and 5 noncreeping plants with decreasing breadth of crown), Heinrichs and Morley (1962) suggested that laborious scoring systems may not be necessary in assessing plants for creep. At the Eighteenth Alfalfa Improvement Conference at Davis, California, Heinrichs (1962) reported that plants which were scored strongly creeping produced very few more creeping-rooted progenies than those scored only slightly creeping. These results are somewhat at variance with those of Heinrichs ( 1954) and Jones and Hanson (1958), who found the phenotypic correlation between width of plant and per cent plants creeping-rooted to be 0.59 and 0.183, respectively. The genetic picture to date appears to suggest that the creeping-root character is complexly inherited, many modifying genes having an effect on its expression. The fact that practically no 100 per cent creepingrooted lines have been obtained from intercrosses between creepers selected for the character through several generations lends support to this hypothesis. However, the high proportion of additive genotypic variance occurring relative to nonadditive for the character is encouraging to the plant breeder who is concerned with developing creepingrooted strains.
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VI. Association of the Creeping-Root Character with Other Plant Characters
At Swift Current, Saskatchewan, Heinrichs (1954) found the correlation coefficient between winterkilling and degree of creeping-rootedness to be -0.60 in two replicated progeny tests which suffered severe winterkilling during the winter of 1948-1949. In a 2-acre breeding nursery that same year, the correlation coefficient between the percentage of 0.51, significant at the 1 per creeping-rooted progenies and vigor was cent level. This indicated that the creeping-rooted plants suffered less winter injury than noncreepers. In a special study on the association of winter injury with creeping-rootedness, Heinrichs and Morley ( 1960) reported the genotypic correlation between the two to be 0.38. Three characters having a bearing on seed production were checked for association with creeping-rootedness by Heinrichs ( 1954) in eight families. He found no correlation between creeping-rootedness and degree of pod coiling in any family; a significant positive correlation between creeping-rootedness and seed set in one family, a negative one in two families, and none in the remaining five; a significant positive correlation between creeping-rootedness and shatterability in one family, a negative one in two, and none in the remaining five. These results
+
+
CREEPING ALFALFAS
333
indicate that pod type, seed set, and seed shatterability were largely independently inherited from creeping-root. Dudley and Hanson (1961),in a study on interrelationships among characters in F2 progenies from crosses between creeping-rooted and hay type alfalfa clones, found that the interaction of creeper x hay type parents was significant only for the characters of plant width, leaf width, and leaf length. The lack of a significant interaction of the other eight characters indicates that for the majority of the characters in these crosses, general combining ability is of more importance at this stage of the breeding program than specific combining ability. VII. Agricultural Performance of Spreading Alfalfas
There has been a lot of speculation about the usefulness of spreading alfalfas for pasture purposes. Much of what has been said in public or written in popular articles during the last decade has been based on what was known about the persistence ability of yellow-flowered alfalfas in their native habitats. Without much experimental evidence to back them up, agronomists, soil conservationists, and plant breeders reasoned that a low, spreading crown hidden from the ravages of the weather and the grazing animal should persist better than protruding crowned taprooted alfalfas. Recent observations and experimental evidence is confirming these earlier expectations. Although very little has been published on the performance of NOMAD as a grazing plant, the originators (Burlingham Seed Company of Forest Grove, Oregon) claim that it persists well under heavy grazing in certain localities in Oregon and adjacent States. E. R. Jackman, farm crops and range specialist in Oregon, for several decades has been stressing the need for a range and pasture legume in the United States. Since NOMAD was released, he observed it in many field plantings and publicized its success as a pasture legume in the press and farm magazines. In recent years the spreading alfalfas NOMAD, RHIZOMA, and RAMBLER have been evaluated in relation to other varieties at a number of institutions in the United States and Canada. Published data on performance are scarce, but indications are that these creeping varieties are rather low yielding outside the region in which they were developed. Such results should not be misconstrued to mean that creeping varieties are not adapted in certain climatic regions because of the creeping character, but rather because these varieties, as such, are not adapted in these regions whether or not they have creeping rootstocks. This point is well illustrated by results from tests in Australia where
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D. H. HEINRICHS
has been compared in relation to locally used varieties (Rogers, 1961; Daday et aZ., 1961). RAMBLERdisplayed extremely low vigor at all locations and produced very low forage yields. Australian scientists, Morley .et al. (1957) and Rogers (196l), have recognized that the creeping-root character from Canadian strains will need to be transferred to locally adapted varieties before it will be of much use under Australian conditions. In New Zealand, Palmer (1959) found that RHIZOMA performed rather poorly compared to other varieties, mainly because of its poor winter growth habit. The variety RAMBLER, developed specifically for use on dryland in the Canadian prairies, persists better than other varieties and even yields better in this region, but not in eastern Canada and in western British Columbia, where the rainfall is much greater and soil conditions are more acidic. On the other hand, NOMAD and RHIZOMA, developed in a moister climate, performed relatively better in eastern Canada and certain areas of British Columbia than RAMBLER. Data on these Canadian results have been presented by Heinrichs and Bolton (1958). Clark (1960) reviewed the results from grazing trials with FWMBLER and other varieties conducted at Swift Current, Saskatchewan, where RAMBLER originated. In all trials RAMBLER persisted better than other varieties except the M.falcatu strains. Typical results from a test grazed by sheep from 1959 to 1962 and shown in Table I. It is significant that RAMBLER
RAMBLER
TABLE I
Relative Stand of a Number of Alfalfa Varieties during a Series of Very Dry Years at Swift Current, Saskatchewan, after Heavy Grazing by Sheep Adequacy of stand Oct. 6, 1958
"/o Basal ground cover ( point-quadrat method)
(%I
May 1960
May 1961
Aug. 1962
RHIZOMA
94 96 97 97
NOMAD
97
RAMBLER
93 83 77 94
12.9 11.9 2.5 11.6 1.1 26.5 28.2 22.0 26.3
7.6 6.3 2.2 10.1 1.0 16.7 16.8 13.0 15.6
5.9 0.7 2.2 7.0 1.1 10.8 14.8 11.5 10.9
Variety LADAK
CRIMM VERNAL
S.C. Syn. 3513 Semipalatinsk Siberian
persisted as well as Semipalatinsk and Siberian, two strains which are representative of the hardy side of its parentage. Both of these strains set very little seed and shatter the little that does set. This precludes the commercial use of these strains. The writer believes that the creeping-
CREEPING ALFALFAS
335
root character inherent in 65 per cent of plants of RAMBLER is partly responsible for its ability to persist, because it cannot be considered to be quite equal to either Semipalatinsk or Siberian in winter hardiness and drought resistance. The Swift Current strain S.C. Syn. 3513 is more strongly creeping-rooted than RAMBLER and excelled both the M. fukutu strains in persistence. The writer has observed that the soil texture and climate have a bearing on how fast a plant will spread by creeping roots, but there is no evidence to show that a truly creeping-rooted plant will not spread in certain climates or on certain soil types. Spreading of plants will occur in pots in the greenhouse as well as in the fields on sandy or clay soils. Rhizomatous spreading plants, on the other hand, will frequently not creep at all under very dry climatic conditions. VIII. The Future of Spreading Alfalfas
Investigational work indicates that spreading alfalfas have a bright future in making the alfalfa crop even more useful than it is today. Although the idea that the creeping habit offers the greatest possibilities in improving the attributes of the crop for pasture ( Aamodt, 1952; Heinrichs, 1954; Graumann, 1958) is sound, there is no doubt that the character can also add a great deal of usefulness to the hay crop. The selfrejuvenation ability of a creeping type after winter injury, heaving, or drought damage should be as important in a hay crop as in a pasture crop. The breeding work done in Canada, the United States, and Australia clearly indicates that the creeping-root character can be transferred from low yielding, poor seed-setting types of plants to high-producing types. The breeding programs which have progressed beyond the second generation indicate that the creeping character often becomes more pronounced in these later generations than was the case in the creepingrooted parental type. It appears that for maximum expression the character must become genetically associated with the growth vigor inherent in alfalfa varieties adapted to any particular environment. In spite of the wide possibilities that seem to be ahead for the creeping character in alfalfa, it should be stressed that the plant breeder perhaps should concentrate his efforts on developing a pasture type because this is where the greatest need lies. It is the vast dry ranges of so many countries that are crying out for a legume that will increase and stabilize production. Persistence as a requirement in the alfalfa variety should be stressed and restressed. It is so easy to stray away from this requirement because most plant breeders and agronomists use yield as
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D. H. HEINRICHS
the ultimate yardstick rather than persistence. E. R. Jackman, Soil Conservationist in Oregon, in a recent letter to the writer, said that research persons tend to have a “yield complex and somehow cannot see that persistence comes first. Many will agree that this is generally true. However, it is not necessarily the plant breeder‘s fault, but perhaps just as much the fault of the agronomist, rangeman, or farmer, who often are slow to accept and get new varieties into use where they should be used. The great need in the future will be the proper evaluation of creepingrooted and rhizomatous alfalfas in relation to varieties of similar adaptivity without the spreading habit. This is the area in which much more research needs to be done before a true assessment of the value of the spreading habit of growth will be forthcoming. Research work on the various types of creepers on an individual plant basis requires investigation before the plant breeder will know exactly the type for which he is selecting. The only detailed investigation of this nature was done by Murray (1955). She found that the rate of spreading varied greatly between creeping-rooted clones. There are sparse creepers and dense creepers and all gradations between. Which type to select for will depend on where and how the alfalfa is to be used. Certainly the agronomic possibilities are great indeed. The term creeping alfalfa would be best not used as a synonym for grazing alfalfa because the two have distinct and different meanings. Nevertheless, it seems logical to suppose that the creeping-root character will make a good grazing alfalfa even better. REFERENCES Aamodt, 0. S. 1952. What’s N e w In Crops Soils 5. Adams, M. W. 1959. J. Genet. 56, 395-400. Adams, M. W., and Semeniuk, G. 1958. S . Dakota State Coll. Agr. Expt. Sta. Bull. 469. Burlingham, E. F. & Sons. Forest Grove, Oregon. Nomad Alfalfa. Camahan, H. L. 1959. Agron. J. 51, 625626. Clark, K. W. 1960. Rept. 17th Alfalfa Imp. Conf. pp. 99-106. Daday, H. 1962. Australian J . Agr. Res. 13, 813-820. Daday, H., Mottershead, B. E., and Rogers, V. E. 1961. Australian J . Exptl. Agr. Animal Husbandy 1, 67-72. Dudley, J. W., and Hanson, C. H. 1961. Crop Sci. 1, 59-63. Edye, L. A., Haydock, K. P., and Saunders, A. M. 1961. Conf. Cereal Pasture Plant Breeders C.S.I.R.O. Canberra Australb 1, 31-1-31-9. Gamer, S. 1922. U.S. Dept. Agr. Bull. 1087. Graumann, H. 0. 1955. Soil Conseru. 21, 103-104. Graumann, H. 0. 1958. What’s New Crops Soils 10. Hansen, N. E. 1909. U.S. Dept. Agr. Bull. 150. Hansen, N. E. 1927. S . Dakota State Coll. Agr. Erpt. Sta. Bull. 224.
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337
Hanson, C. H., Garrison, C. S., and Graumann, H. 0. 1960. US. Dept. Agr. Agr. Handbook 177. Heinrichs, D. H. 1950. Rept. 12th Alfalfa Imp. Conf. pp. 59-61. Heinrichs, D. H. 1954. Can. J. Agr. Scl. 34,269-280. Heinrichs, D.H. 1958. Agr. Inst. Reu. May-June. Heinrichs, D. H. 1959. Can. J. Plant Sci. 39, 384-394. Heinrichs, D. H. 1962. Rep. 18th Alfalfa Imprwement Conf., Daois, Calif., pp.
45-50.
Heinrichs, D. Heinrichs, D. Heinrichs, D. Heinrichs, D.
H., and Bolton, J. L. 1958. Can. Dept. Agr. Publ. 1030. H., and Morley, F. H. W. 1960. Can. 1. Plant Sci. 40,487-489. H., and Morley, F. H. W. 1962. Can. J. Genet. Cytol. 4, 79-89. H., Troelsen, J. E., and Clark, K. W. 1960. Can. J . Plant Sci. 40,
638-644.
Jones, A., and Hanson, C. H. 1959. Agron. J. 51, 710-718. Komarov, V. L. 1945. Flora URSR 11, 129-176. Ludwig, L. J. 1960. M.S.Dissertation, University of New Zealand. Morley, F. H. W., and Heinrichs, D. H. 1960. Can. 1. Plant Sci. 40,424-433. Morley, F. H. W., Daday, H., and Peak, J. W. 1957. Australian J. Agr. Res. 8,
635-651.
Murray, B. E. 1955. Ph.D. Dissertation, Cornell Univ., Ithaca, New York. Murray, B. E. 1957. Can. J. Botany 35, 463-475. Nilan, R. A. 1951. Sct. Agr. 31, 123-127. Oakley, R. A,,and Carver, S. 1913. US. Dept. Agr. Bur. Plant Ind. Circ. 115. Oakley, R. A., and Garver, S. 1917. U.S. Dept. Agr. Bull. 428. Odland, T. E., and Skogley, C. R. 1953. Agron. J. 45, 243-245. Oliver, G. W. 1913. U.S. Dept. Agr. Bur. Plant Ind. Bull. 258. Palmer, T. P. 1959. New Zealand J . Agr. Res. 2, 1195-1202. Rogers, V. E. 1961. Australtan J. Exptl. Agr. Animal Husbandry 1, 80-66. Smith, D. 1950. Agron. J. 42, 398-401. Smith, D. 1951. Agron. J . 43, 573-575. Smith, D. 1955. Agron. 1. 47, 588-589. Southworth, W. 1921. Scl. Agr. 1, 5-9.
D. H.
Heinrichs
Canada Department of Agriculture, Swift Current, Saskatchewan, Canada
I. Introduction ................................................ 11. Types of Root Systems in Alfalfa .............................. A. Rhizomatous Plants ...................................... B. Creeping-Rooted Plants ................................... 111. Physiological Considerations ................................... IV. Breeding for the Creeping-Root Character ....................... V. Genetics of the Creeping-Root Character ....................... VI. Association of the Creeping-Root Character with Other Plant Characters VII. Agricultural Performance of Spreading Alfalfas ................... VIII. The Future of Spreading Alfalfas ............................... References ..................................................
Page 317 319 321 322 325 327 331 332 333 335 336
I. Introduction
The existence of creeping alfalfas has been known at least as far back as the turn of the century. During his trips to Russia and Siberia as Agricultural Explorer for the United States Department of Agriculture (1897-1898, 1906, 1908-1909), N. E. Hansen observed creeping plants in varieties of wild growing, yellow-flowered alfalfa ( Medicago falcata L. ) at several locations. In his account, Hansen (1909) reports that Klingen, a Russian agronomist, found as many as one hundred branches on one plant of M . falcata. He states, “the plants of the variety grow upright on the steppe but if pastured closely, they creep and only the ends are erect.” Hansen mentions that the native M . falcata strains in the Volga region of eastern European Russia endure pasturing, whereas introduced strains of Medicago sativa L. do not. In a later publication (Hansen, 1927), he says this about M . falcata he observed in Orenburg province: “Some people are interested in this variety because of its habit of sprouting from the roots at some distance from the original crown.” Oakley and Garver ( 1913, 1917), Oliver ( 1913), Garver (1922), and Southworth (1921) studied various root systems of alfalfa. The general conclusions arrived at by these workers are perhaps best summarized by Southworth, who states: “The hardiness of alfalfa depends very largely 317
318
D. H. HEINRICHS
on its root system. Plants possessing a branched-root system are much better able to withstand heaving than those having only a single taproot, no matter how great its length may be. Those plants which have the power to produce rooting underground stems are able to renovate themselves, and after the death of the main rootstock are capable of keeping up a separate existence quite independent of the parent rootstock. When alfalfa has the habit of spreading by means of root proliferation, we have a form of spreading and multiplying in a vegetative manner which promises to give the plant greater powers of resistance to cold and also greater powers of recuperation from injury than is possessed by even true rhizomes, and we venture to hope that these properties will render it possible to grow good crops in adverse climatic conditions under which it would be quite impossible to raise common alfalfa.” This statement suggests many possibilities of expansion for the alfalfa crop and has many agricultural implications. Small samples of M . falcata were distributed quite widely to farmers during the early 1920’s from Brookings, South Dakota, where Dr. N. E. Hansen was stationed. Although a few plantings from the original seed distribution were successful, very little of agricultural significance resulted from them, probably because of very low seed yields or lack of follow-up by plant breeders and agronomists. Nevertheless, the foundation for extending alfalfa use into drought-ridden areas had been laid, and a number of plant breeders, as well as farmers, retained an interest in the yellow-flowered alfalfas. After the widespread drought of the 1930’s in the Northern Great Plains region of North America, it was noted that certain M . falcatn plantings had come through the dry period with very little reduction in stand. Four plantings were known in Canada and an undetermined number in the United States. A very successful planting was that of Claude Foster at Coal Springs, South Dakota. The alfalfa in this planting exhibited the creeping-root character to a considerable degree. Very little use under cultivation has been made of the native alfalfas of Russian and Siberian origin within the U.S.S.R. itself. This can be gathered from a statement by Komarov (1945): “Nearly all the wild lucernes within the limits of the U.S.S.R. have up to the present been scarcely tried in cultivation. Their nutritive qualities and the drought resistance of some of the species led us to believe that upon their introduction into cultivation, these species will play a not insignificant role in the problem of reclamation of the desert areas and wastelands of the U.S.S.R.” That the creeping-root character was manifest in some of these species is indicated by certain root descriptions given in the book. Renewed interest in creeping types of alfalfa paralleled the interest
CREEPING ALFALFAS
319
in regrassing and soil conservation in North America ( Aamodt, 1952). It was the apparent need for a persistent legume that started a number of breeding programs in the United States and Canada which undertook to develop more drought-resistant and winter-hardy varieties. Alfalfa breeders at several research institutions began to hybridize plants of M . falcuta and M.sutiva extensively in their breeding programs and discovered spreading plants within the F1 and later generations. Four varieties possessing the spreading habit to a certain degree have been developed as a result of breeding: RHIZOMA released in 1948 (Nilan, 1951), RAMBLER released in 1955 ( Heinrichs and Bolton, 1958), TETON released in 1958 ( Adams and Semeniuk, 1958), and NOMAD released in 1951 (Burlingham & Sons). The breeding program at the Experimental Farm, Swift Current, Saskatchewan, started by Dr. S. E. Clarke (Heinrichs, 1954) did more to stimulate intercst in development of creeping-rooted types of alfalfa than any other recent program. Breeding stock of creeping alfalfa was distributed freely to research institutions in many parts of the world and is being widely used in breeding programs aiming to develop creepingrooted strains. Until very recently, creeping alfalfas were considered to be useful mainly for pastures ( Aamodt, 1952; Heinrichs, 1954; Graumann, 1955, 1958). However, this does not mean that the creeping-root character, if present in high-yielding, quick-recovering hay types, might not add to their usefulness. In recent breeding studies involving creepers of northern origin and high-yielding southern varieties, it has been shown that the creeping-root character is not very closely linked with winter dormancy (Dudley and Hanson, 1961; Edye et al., 1961; Daday, 1962). The character therefore promises to have a much wider application in broadening the usefulness of alfalfa than had been previously believed to be possible. II. Types of Root Systems in Alfalfa
Most of the cultivated alfalfa varieties have a tap-root system. This type of root system is characteristic of varieties originating from M . sativa L. A tap-rooted plant has a rather narrow protruding crown, the tap root penetrating vertically into the ground with branch roots arising at intervals from it. Such plants are unable to spread sideways except to a limited degree by crown expansion as the plant ages. The branch-rooted alfalfa varieties and those with a proportion of both branch and tap roots are of more recent origin. The varieties used in North America differ widely in the extent to which their primary roots are branching (Smith, 1951). These types have variegated flowers and
320
D. H. HEINRICHS
are considered to have originated from natural or artificial crosses between M . satiua and M . falcata; they are often designated as M . media Pers. The majority of such varieties have been developed in northern areas where winters are cold or in areas which are cold because of high elevation. The variety LADAK, a typical variegated variety, with a branched-root system, came from a natural population in the province of Ladakh, India. A branch-rooted plant differs from a tap-rooted plant in that a number of main primary roots arise from the crown instead of only one, and the crown is inclined to be wider. Such plants are able to develop adventitious shoots from the roots. This was demonstrated by Smith (1950), who found that adventitious shoots developed on root segments of LADAK and an M . falcata strain, but not on plants of GRIMM, RANGER, COSSACK, and MONTANA COMMON. Murray (1955) found that adventitious shoots developed also on plants of LADAK, but to a lesser degree than on creeping-rooted plants. Branch-rooted plants are able to withstand heaving during unfavorable winters better than tap-rooted plants. This has been found to be the case in the variety NARRAGANSETT, which is described as having a much-branched root system (Odland and Skogley, 1953). Although the branched-root system in alfalfa can be considered to result in a slight tendency for the plant to spread horizontally, the spread is restricted to the above-surface crown. There are two types of root systems in alfalfa which enable the plant to spread horizontally. These are generally referred to as rhizomatous and creeping-rooted. In the first instance, the spread is attributed to lateral expansion of the low-set crown by short horizontal stems, and in the second the spread is brought about by horizontal roots from which shoots may arise at irregular intervals, Graumann (1955,1958) explains the difference between rhizomatous and creeping-rooted type of spread quite adequately. He also makes it clear that any one strain or variety may have in it a variety of crown and root types. The difference between the two types of spread often is not too clearly demarcated or too well understood, and therefore each will be dealt with under a separate heading. Four types of plants representing different degrees of spread and different root systems are illustrated in Fig. 1. The plants shown in this photograph were excavated in October, 1962, from.an old stand of M . falcata growing on the Experimental Farm, Swift Current, Saskatchewan. This strain is one of N. E. Hansen’s introductions from Siberia, probably the strain known as Semipalatinsk. These plants although differing greatly from one another in ability to spread, have one characteristic in common, and that is the low crown which is located mostly below the soil surface. The low crown, perhaps, is the characteristic in M. falcata
CREEPING ALFALFAS
321
which differentiates it from M. sutivu to a greater extent than the roots themselves. Excellent descriptions and photographs of different crown and root systems and their relationships to types of alfalfa have been
FIG. 1. Plants of M . falcata, probably of the strain Semipalatinsk, excavated in September, 1962, in a 25-year-old field of crested wheatgrass at the Experimetal Farm, Swift Current, Saskatchewan. The alfalfa was an experimental planting seeded the same time as the grass. The photograph shows the deep-set crown of all plants and the different root systems, Left to right: tap root, branch root, rhizomatous root, creeping root.
presented by Garver ( 1922). Garver’s descriptions parallel closely what is said about roots in this article, suggesting that in the study of various alfalfa root systems little progress has been made during the last forty years. A. RHIZOMATOUSPLANTS The rhizomatous type of spread in alfalfa has been described in some detail by Oliver ( 1913) and more recently by Graumann (1958). The spreading of this type of plant is assumed to arise from stems of rootlike appearance which are initiated from the original primary root axis. These rhizomes extend laterally for varying distances, eventually root over part of their length, and emerge from the soil as vegetative stems. Dr.
322
D. H. HEINRICHS
G. G. Moe of the University of British Columbia developed the variety which typifies this type of crown and roots (Nilan, 1951). Smith ( 1955) investigated the underground crown branches ( rhizomes) of a number of varieties. Of the varieties tested, RHIZOMA had the most rhizomes and ARIZONA COMMON the least. There seemed to be a direct relationship between the quantity of rhizomes and the amount of hl. falcatu which figured in the parentage of the varieties. Hanson et al. (1960) express the same thought in Agricultural Handbook No. 177. NOMAD is another new variety with extensive rhizome development ( Aamodt, 1952). It has been observed by Heinrichs (1954) that RHIZOMA and NOMAD do not spread to any extent in the arid climate of the prairie region of Canada. He attributed the lack of rhizomatic spread to inadequate soil nioisture conditions at the surface. Hanson et al. (1960) make the observation that RHIZOMA and NOMAD do not show much tendency to spread in many regions of the United States. The writer is of the opinion that rhizomatic plants will tend to spread quite strongly if climatic conditions are humid and the surface soil is moist for prolonged periods, particularly in the fall. Rooting may occur not only from underground stems, but also from prostrate stems lying on the soil surface. If animals graze and trample rhizomatous plants during such moist periods, the plants will tend to spread even more rapidly than when left ungrazed because the stems may grow more prostrate and thus get tramped into the ground where they can root from the nodes. Rhizomatous plants generally expand in crown width, and the top growth from them is very dense per unit area (Fig. 1 ) . RHIZOMA
B. CREEPINGROOTED PLANTS Truly creeping-rooted plants were described and illustrated by Oakley and Garver (1913), Oakley (1917), Southworth ( 1921), and Garver ( 1922). Recent descriptions and illustrations of this type were presented by Heinrichs ( 1954), Murray (1955), and Heinrichs and Bolton ( 1958). Actually, when creeping-rooted plants showed up in breeding populations resulting from intercrosses between M . falcuta and plants of the varieties LADAK and RHIZOMA, it seemed as though a new discovery had been made. This was the impression because certain hybrids were expressing the spreading habit to a much greater extent than any M . falcata parent. This accentuated spread in hybrid forms appeared to be due to complementary gene effects rather than to hybrid vigor (Heinrichs, 1954). A typical creeping root of a hybrid type is shown in Fig. 2 and of growing plants in Fig. 3. The creeping rootstocks are generally found to be 4 to 8 inches below the surface of the ground. They send up
CREEPING ALFALFAS
323
shoots at intervals, each of which is capable of becoming an independent plant. Some plants are dense creepers, others sparse; that is, certain plants produce more shoots per unit area than others. The sparse type of creeper may be the more desirable type for dryland pastures than
FIG. 2. A typical creeping-rooted plant which shows M . satiua as well as M . fakutu characteristics. The creeping-root development is more distinct than is the case in plant 4 in Fig. 1, which tends to display a combination of rhizomatous and creeping-root development. The pedigree of this plant in terms of varieties is: LADAK x (LADAK X M . f&ai%).
the dense type because in a mixed stand the alfalfa and grass plants will tend to form an interspersed association. Also, there will be less tendency for the stand to become too thick during favorable moisture years, with subsequent lower productive capacity in dry years. Murray (1957) studied the ontogeny of adventitious stems on roots
324
D. H. HEINRICHS
of creeping-rooted alfalfa. She found that the horizontal roots are anatomically true root structures resembling the primary roots. They produce adventitious stems on a much greater range of roots than branch roots. Murray states: “At successive intervals of time in the ontogeny of adventitious stems, there are certain changes which occur within the root during two intimately associated phases of activity. One phase is the initiation and development, at the periphery of the root, of a primordial dome. The other is the differentiation of the subjacent secondary phloem parenchyma cells to form a meristematic zone in which vascular
FIG. 3. Early spring growth showing the spread of strongly creeping-rooted plants, 5 years old. The planting in this nursery originally was 6 feet each way. The plots contained 4 plants of a clonal line, Note that the creeping-rooted plants are encroaching on the noncreepers.
tissues differentiate and connect the peripheral primordia with the cambium of the root.” She further states that the inherent difference in creeping-rooted and noncreeping-rooted plants is in some way associated with the ability of the former to initiate stem primordia on all roots, whereas in the latter this ability is restricted to very few roots and perhaps is seldom brought into function. The writer observed, in the spring of 1962, when severe winter injury occurred in spaced populations, that some branch-rooted plants sent up new shoots from the roots located 4 to 6 inches underground when the main crown had been destroyed as a result of winter injury. Thus, it may be that in noncreeping plants, adventitious shoots are developed mainly under stress conditions.
CREEPING ALFALFAS
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111. Physiologic01 Considerations
It is a fact that most of the spreading types of alfalfa presently being used as forage crops or for breeding purposes originated in northern areas where the winters are long and cold. It is natural, therefore, that most spreading alfalfas have long dormant periods in their growth cycles and slow regrowth characteristics. The spreading character as such, however, is not restricted to northern types. Oliver (1913) reports rhizome development in native varieties found in northern Africa. He states that the principal functions of the large rhizome may be the storage of water to tide the plants over the very hot and dry summers, because the rhizomes of these plants in northern Africa are evidently formed at the close of the growing season, which is during the winter months, but when brought to a colder climate they form during the autumn months. Aamodt (1952) mentions that wild forms of spreading alfalfas were found in Turkey by H. L. Westover in 1931. These alfalfas were growing in desertlike, denuded fields which the natives call “goat pastures.” Rhizomatous types were also found in Spain and Greece growing along roadsides, in fence rows, and in pastures among grasses. These observations suggest that drought resistance and ability to grow under competition and stress may be the common denominator, rather than cold resistance of the wild forms of spreading alfalfas. Plant breeders in subtropical and tropical climates may be well advised to consider using Mediterranean or Turkish wild alfalfa types in their programs aiming to develop persistent pasture types for their climatic conditions rather than those from northern regions. To the knowledge of the writer there is limited information from physiological studies on spreading alfalfas that relate the rhizomatous or creeping-root characteristic with any clearly defined physiological function. Ludwig (1960) used the technique of “growth analysis” to relate the main environmental factors on the early growth of a creepingrooted clonal Iine selected out of Canadian material. He found that number of plants with adventitious shoots was increased by short days, high light intensities, and high day and night temperatures. The number of adventitious shoots per plant was increased by the same environmental factors. Adventitious shoot production appeared to be directly associated with the growth rate of the roots and the top-to-root ratio, and indirectly with the net assimilation rate. Generally, those environmental factors which increased the net assimilation rate or decreased the top-to-root ratio, increased root growth and the production of ad-
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D. H. HELNRICHS
ventitious stems. Root segments removed from plants in each environmental treatment and placed in sand in the greenhouse all produced adventitious shoots. This indicates that the environment in which the plants had been growing had little effect on the potential of roots to form adventitious shoots. Since Ludwig’s study was done on a creeping-rooted clone of northern origin the root responses to environmental changes may be directly associated with this particular genotype, That creeping-rooted clones of different growth form may respond differently to environmental conditions in the formation of adventitious shoots, is indicated by results from a recent study by Ludwig (personal correspondence). He found that although in the majority of genotypes daylength had very little effect on the production of adventitious shoots, one clone produced many adventitious shoots in long days but scarcely any in short days, and another produced many shoots on the roots in short days, but scarcely any in long days. The initiation of adventitious shoots, Murray (1957) points out, is likely to involve an interrelationship of many factors. These could be physical ( size and number of primordia), physiological ( chemical stimulus for differentiation and growth and environmental responses), and genetic (an inherent characteristic of the plant). There is no doubt that more knowledge of the nongenetic mechanisms which influence adventitious stem formation would be very useful to the plant breeder in understanding hereditary factors and to the agronomist in forecasting where the creeping type might fit into a particular environment. Winter hardiness relationships among a number of varieties, three of which were of the spreading type, were reported by Heinrichs and Bolton (19%)) Heinrichs (1958, 1959)) and Heinrichs et aZ. (1960). It was quite obvious from the results that increased winter hardiness cannot be attributed to the spreading habit of growth alone. The character must be present in an inherently winter-hardy type. Thus, NOMAD, a spreading variety, was much less persistent in the Prairie Provinces of Canada than the nonspreading varieties VERNAL, GRIMM, and LADAK, which are commonly grown in the area. On the other hand, the creepingrooted variety RAMBLER, which possesses adequate winter hardiness, maintained a better stand than any other variety. This situation was also shown by Clark (1960). That creeping-rooted alfalfas may survive better than noncreepers of similar genotype was noted by Heinrichs (1954). He states: “In creeping-rooted plants, when the main crown was dead, numerous shoots appeared from creeping rootstocks at a considerable distance from the crown. It appeared that killing of the main crown actually stimulated development of aerial shoots from creeping root-
CREEPING ALFALFAS
327
stocks.” It can be reasoned, therefore, that heaving damage or severe overgrazing may similarly stimulate plants to spread. In Australia, Morley et al. (1957) investigated Canadian creepingrooted clones, locally adapted clones, and intercrosses between them for reaction to temperature and day length. They found that clones differed greatly in their reaction to these two environmental factors. The creeping-rooted clones from Canada were very low in winter production because of the winter dormancy characteristic. They state that although introduction of alfalfa breeding material from these northern regions is undoubtedly justified, the concomitant winter dormancy must be eliminated before derived strains can be unreservedly recommended for Australian conditions. In a recent physiological study, Daday (1962) showed that although RAMBLER required short days and low temperatures for best development of creeping roots, the F2 and F3 creeping derivatives from RAMBLER crossed with AFRICAN, HAIRY PERUVIAN, and HUNTER RIVER developed creeping roots satisfactorily when days were longer and temperatures higher. When considering the use of spreading alfalfas in any particular region, one dare not leave out consideration of the environment at their point of origin. The potential real usefulness of the creeping character may never be realized unless it is transferred by breeding to strains physiologically adapted to a specific environment. IV. Breeding for the Creeping-Root Character
Oakley and Carver (1913, 1917) reviewed the agronomic possibilities that lie in the development of new alfalfa strains by hybridizing forms of M. falcata and M . satiua. Superior drought resistance and winter hardiness were considered to be the main desirable characters of M . fulcuta, and they pointed to the role this species has already played in the formation of useful varieties as a result of natural crossing. GRIMMis mentioned as an outstanding example of such a variety. They also envisaged that by the use of the proliferating root character, high-yielding strains may be originated that will be especially resistant to severe climatic conditions and actually aggressive on soils of fairly loose texture. Breeding programs using the principle of combining characters of the two species into more useful varieties were almost at a standstill until after the Great Drought of the 1930’s in the Great Plains area of North America. In Canada such a breeding program was undertaken in 1938 at the Experimental Farm, Swift Current, Saskatchewan, and the aims were outlined by Heinrichs ( 1954). He states that the objective was to combine the winter-hardy and persistence qualities of M . fulcata
328
D. H.HEINRICHS
with good seed-producing qualities of common varieties. The breeding procedure followed was based on determination of the combining ability of individual plants. It was the rediscovery of strongly creeping-rooted types in the hybrid populations that led to concerted efforts to develop a creeping-rooted variety adapted to conditions in the Canadian prairies. Principles of general and specific combining ability were used to evaluate creeping-rooted selections for transmission of this character along with other useful agronomic characters to their progenies. The breeding objective was finally reached in 1955 with the release of the variety RAMBLER ( Heinrichs and Bolton, 1958). Interest of alfalfa breeders of North America in creeping-rooted types of alfalfa was greatly stimulated at the Twelfth Alfalfa Improvement Conference held in Lethbridge, Alberta. At this conference a paper on the subject was presented by Heinrichs (1950) and field demonstrations of spreading plants were shown. Breeding stock of creeping-rooted alfalfa was sent out from the Experimental Farm, Swift Current, Saskatchewan, to a great many institutions in all parts of the world. In addition, the strains of M . falcata and M . falcata X M . sativa origin available at the South Dakota Agricultural Experiment Station, Brookings, South Dakota, were a good source of the creeping character. These could be traced back to N. E. Hansen’s alfalfa introductions from Europe and Asia. At the present time substantial breeding projects, aiming to develop suitable creeping-rooted strains for specific environments, are underway at the following institutions: United States of America Crops Research Division, U.S.D.A. and North Carolina State College, Raleigh, North Carolina. John W. Dudley. Department of Plant Breeding, Cornell University, Ithaca, New York. C. C. Lowe and R. E. Anderson. Nevada Agricultural Experiment Station, Reno, Nevada. H. L. Camahan. Crops Research Division, U.S.D.A. and University of Nebraska, Lincoln, Nebraska. W. R. Kehr. South Dakota Agricultural Experiment Station, Brookings, South Dakota. M. D. Rumbaugh. Kansas State University, Manhattan, Kansas. E. L. Sorenson. Canada Experimental Farm, C.D.A., Swift Current, Saskatchewan. D. H. Heinrichs. Research Station, C.D.A., Lethbridge, Alberta. M. R. Hanna. Genetics and Plant Breeding Research Institute, C.D.A., Ottawa, Ontario. H. A. McLennan. Chile Oficina Estudios Especiales, Casilla 2-P, Santiago. Avendano T. Raul and Ruco E. Osvaldo.
CREEPING ALFALFAS
329
Australia Division of Plant Industry, C.S.I.R.O., Canberra. H. Daday and F. H. W. Morley. Division of Tropical Pastures, C.S.I.R.O., Brisbane. E. H. Hutton and L. A. Edye New Zealand Crop Research Division, D.S.I.R., Christchurch. T. P. Palmer. Great Britain Welsh Plant Breeding Station, Aberystwyth, Wales. W. Ellis Davis. Denmark Forsogsgarden Hojbakkegard. Albertslund pr. Taastrup. H. J. Moller Nielsen.
Methods of breeding for the creeping-root character need to differ little from those used for other quantitatively inherited characters. Heinrichs (1954) states that determination of combining ability of individual plants appears to be a good method for evaluating the capacity to transmit creeping-rootedness to progenies. The best time to score for degree of creeping-root development was in the spring, one year after planting. Creeping-rootedness, however, did not express itself in all plants until two or even three years after planting at Swift Current, Saskatchewan. In a later study of similar material, Morley and Heinrichs (19so) found that general combining ability was more important than specific combining ability, and therefore they concluded that mass selection would be very efficient in breeding for creeping-root. Jones and Hanson (1959) crossed the varieties AFRICAN, BUFFALO, CALNEFDE, and nine North Carolina clones on three Canadian creepers, and in the F2 recovered creeping-rooted plants from crosses with each of the varieties. The North Carolina selections transmitted different amounts of creep to their progenies, indicating the association of complementary factors with the expression of creeping roots. They also observed that the inherent vigor of plants has a bearing on expression of the creeping growth habit. Australian alfalfa breeders are concerned with combining the creeping-root character from Canadian creepers with summer and winter growth habits of subtropical and tropical alfalfas. The writer spent 10 months in Australia during 1961 and was quite impressed with the progress being made at the Fs generation level. The Canadian creepers show creep development in Australia but lack growth vigor, and in Queensland they produce practically nothing. In the F3 generation extremely vigorous creepers were found, as Edye et uZ. (1961) and Daday ( 1962) have shown (Fig. 4). Edye et al. concluded that mass selection for creeping-rootedness in the third and later generations should be an efficient method of breeding. Daday found that the varieties HUNTER RIVER, HAIRY PERUVIAN, and AFRICAN in crosses with RAMBLER produced only 5 per cent creepers in F1 but an average of 41 per cent in the F3 generation resulting from intercrosses of F2 creepers. The range
330
D. H. HEINRICHS
in creep between F3 lines was 0 to 81 per cent (Fig. 4).This compares quite favorably with plantings observed by Heinrichs (1954), who used the northern varieties LADAK and RHIZOMA in his breeding program. In a breeding program initiated at the U S . Regional Pasture Laboratory, University Park, Pennsylvania, Carnahan ( 1959) investigated
FIG. 4. An alfslfa breeding nursery at C.S.I.R.O., Canberra, Australia. The population is second and third generation material from crosses between Canadian creepers and African, DuPuits, and Hunter River selections. The stakes mark the creeping-rooted plants. The photograph was taken near the end of August (end of winter). Note the different degrees of winter dormancy.
methods of evaluating alfalfa for the creeping-root character. He found that creeping root expressed itself with the same expectation in nurseries oversown with timothy as in cultivated nurseries. The work involved in the oversown nurseries was less and, considering that the alfalfa will likely be grown in association with grass, such nurseries may be preferable for evaluating the alfalfa plants for creep development. When considering the breeding programs conducted at widely separated locations, there seems to be unanimity of opinion that fairly rapid progress is possible by following accepted breeding practices based on progeny performance. It also appears obvious that the creeping character must be transferred to varieties adapted to a particular climate before it can display its usefulness in improving persistence.
CREEPING ALFALFAS
331
V. Genetics of the Creeping-Root Character
The variation in type of spreading root systems and the overlapping that appears to occur between one type and another (Fig. 1 ) would tend to lead one to assume that the inheritance of this character might be complex. Heinrichs (1954) proceeded to breed for creeping root on the assumption that the character was a quantitative one. The data he obtained from combining ability tests of creeping-rooted selections seem to justify the assumption, and he concluded that the character appears to be a quantitative one with complementary factors playing a part. Morley and Heinrichs (1960) statistically examined the data obtained on the creeping-root character from a large population of alfalfa grown in experimental blocks at Swift Current, Saskatchewan. Their analysis showed that the estimate of Cov. (full sibs)-Cov. (half sibs) was 0.062, and of Cov. (half sibs) was 0.091, indicating that the genotypic variation was predominantly additive. In a study on estimates of variance in root proliferation in alfalfa, Adams (1959) found that the genotypic variance for extent of creep was mostly nonadditive and not highly heritable. In his analysis, however, Adams did not include the noncreeping fraction of the progenies, and, hence, the results give no information on the inheritance of creeping-root development versus no creep development. Further light on this apparent discrepancy was shed by a study by Heinrichs and Morley (1962). They found that when the data from the entire population were analyzed the genotypic variance was predominantly additive, but when only the creeping fraction was examined the genotypic variance was largely nonadditive. The conclusion drawn from this finding was that the creeping-root character versus tap- or branch-root character is quite highly heritable but the degree of spread is influenced strongly by nonadditive genotypic and environmental factors and perhaps by genes determining vigor of growth, as Jones and Hanson (1959) suggested. Daday (1962), working with a population of a somewhat different background, found considerably more of the variance to be due to nonadditive genetic effects than did Morley and Heinrichs ( 1960) and Heinrichs and Morley (1962). The heritabilities reported for the creeping-root character are quite good, varying from 20 per cent (Morley and Heinrichs, 1960) to 31 per cent (Heinrichs and Morley, 1962), calculated on the individual plot basis. Low heritability, reported by Adams (lQSQ),was substantiated by Heinrichs and Morley (l%2), but applied o d y to degree or extent of spread. Based on the fact that the data from a simple two-way classification into creeping and noncreeping plants gave approximately the
332
D. H. HEINFUCHS
same heritability estimates as those from five scores (1, 2, and 3 representing degrees of creep, and 4 and 5 noncreeping plants with decreasing breadth of crown), Heinrichs and Morley (1962) suggested that laborious scoring systems may not be necessary in assessing plants for creep. At the Eighteenth Alfalfa Improvement Conference at Davis, California, Heinrichs (1962) reported that plants which were scored strongly creeping produced very few more creeping-rooted progenies than those scored only slightly creeping. These results are somewhat at variance with those of Heinrichs ( 1954) and Jones and Hanson (1958), who found the phenotypic correlation between width of plant and per cent plants creeping-rooted to be 0.59 and 0.183, respectively. The genetic picture to date appears to suggest that the creeping-root character is complexly inherited, many modifying genes having an effect on its expression. The fact that practically no 100 per cent creepingrooted lines have been obtained from intercrosses between creepers selected for the character through several generations lends support to this hypothesis. However, the high proportion of additive genotypic variance occurring relative to nonadditive for the character is encouraging to the plant breeder who is concerned with developing creepingrooted strains.
+
+
VI. Association of the Creeping-Root Character with Other Plant Characters
At Swift Current, Saskatchewan, Heinrichs (1954) found the correlation coefficient between winterkilling and degree of creeping-rootedness to be -0.60 in two replicated progeny tests which suffered severe winterkilling during the winter of 1948-1949. In a 2-acre breeding nursery that same year, the correlation coefficient between the percentage of 0.51, significant at the 1 per creeping-rooted progenies and vigor was cent level. This indicated that the creeping-rooted plants suffered less winter injury than noncreepers. In a special study on the association of winter injury with creeping-rootedness, Heinrichs and Morley ( 1960) reported the genotypic correlation between the two to be 0.38. Three characters having a bearing on seed production were checked for association with creeping-rootedness by Heinrichs ( 1954) in eight families. He found no correlation between creeping-rootedness and degree of pod coiling in any family; a significant positive correlation between creeping-rootedness and seed set in one family, a negative one in two families, and none in the remaining five; a significant positive correlation between creeping-rootedness and shatterability in one family, a negative one in two, and none in the remaining five. These results
+
+
CREEPING ALFALFAS
333
indicate that pod type, seed set, and seed shatterability were largely independently inherited from creeping-root. Dudley and Hanson (1961),in a study on interrelationships among characters in F2 progenies from crosses between creeping-rooted and hay type alfalfa clones, found that the interaction of creeper x hay type parents was significant only for the characters of plant width, leaf width, and leaf length. The lack of a significant interaction of the other eight characters indicates that for the majority of the characters in these crosses, general combining ability is of more importance at this stage of the breeding program than specific combining ability. VII. Agricultural Performance of Spreading Alfalfas
There has been a lot of speculation about the usefulness of spreading alfalfas for pasture purposes. Much of what has been said in public or written in popular articles during the last decade has been based on what was known about the persistence ability of yellow-flowered alfalfas in their native habitats. Without much experimental evidence to back them up, agronomists, soil conservationists, and plant breeders reasoned that a low, spreading crown hidden from the ravages of the weather and the grazing animal should persist better than protruding crowned taprooted alfalfas. Recent observations and experimental evidence is confirming these earlier expectations. Although very little has been published on the performance of NOMAD as a grazing plant, the originators (Burlingham Seed Company of Forest Grove, Oregon) claim that it persists well under heavy grazing in certain localities in Oregon and adjacent States. E. R. Jackman, farm crops and range specialist in Oregon, for several decades has been stressing the need for a range and pasture legume in the United States. Since NOMAD was released, he observed it in many field plantings and publicized its success as a pasture legume in the press and farm magazines. In recent years the spreading alfalfas NOMAD, RHIZOMA, and RAMBLER have been evaluated in relation to other varieties at a number of institutions in the United States and Canada. Published data on performance are scarce, but indications are that these creeping varieties are rather low yielding outside the region in which they were developed. Such results should not be misconstrued to mean that creeping varieties are not adapted in certain climatic regions because of the creeping character, but rather because these varieties, as such, are not adapted in these regions whether or not they have creeping rootstocks. This point is well illustrated by results from tests in Australia where
334
D. H. HEINRICHS
has been compared in relation to locally used varieties (Rogers, 1961; Daday et aZ., 1961). RAMBLERdisplayed extremely low vigor at all locations and produced very low forage yields. Australian scientists, Morley .et al. (1957) and Rogers (196l), have recognized that the creeping-root character from Canadian strains will need to be transferred to locally adapted varieties before it will be of much use under Australian conditions. In New Zealand, Palmer (1959) found that RHIZOMA performed rather poorly compared to other varieties, mainly because of its poor winter growth habit. The variety RAMBLER, developed specifically for use on dryland in the Canadian prairies, persists better than other varieties and even yields better in this region, but not in eastern Canada and in western British Columbia, where the rainfall is much greater and soil conditions are more acidic. On the other hand, NOMAD and RHIZOMA, developed in a moister climate, performed relatively better in eastern Canada and certain areas of British Columbia than RAMBLER. Data on these Canadian results have been presented by Heinrichs and Bolton (1958). Clark (1960) reviewed the results from grazing trials with FWMBLER and other varieties conducted at Swift Current, Saskatchewan, where RAMBLER originated. In all trials RAMBLER persisted better than other varieties except the M.falcatu strains. Typical results from a test grazed by sheep from 1959 to 1962 and shown in Table I. It is significant that RAMBLER
RAMBLER
TABLE I
Relative Stand of a Number of Alfalfa Varieties during a Series of Very Dry Years at Swift Current, Saskatchewan, after Heavy Grazing by Sheep Adequacy of stand Oct. 6, 1958
"/o Basal ground cover ( point-quadrat method)
(%I
May 1960
May 1961
Aug. 1962
RHIZOMA
94 96 97 97
NOMAD
97
RAMBLER
93 83 77 94
12.9 11.9 2.5 11.6 1.1 26.5 28.2 22.0 26.3
7.6 6.3 2.2 10.1 1.0 16.7 16.8 13.0 15.6
5.9 0.7 2.2 7.0 1.1 10.8 14.8 11.5 10.9
Variety LADAK
CRIMM VERNAL
S.C. Syn. 3513 Semipalatinsk Siberian
persisted as well as Semipalatinsk and Siberian, two strains which are representative of the hardy side of its parentage. Both of these strains set very little seed and shatter the little that does set. This precludes the commercial use of these strains. The writer believes that the creeping-
CREEPING ALFALFAS
335
root character inherent in 65 per cent of plants of RAMBLER is partly responsible for its ability to persist, because it cannot be considered to be quite equal to either Semipalatinsk or Siberian in winter hardiness and drought resistance. The Swift Current strain S.C. Syn. 3513 is more strongly creeping-rooted than RAMBLER and excelled both the M. fukutu strains in persistence. The writer has observed that the soil texture and climate have a bearing on how fast a plant will spread by creeping roots, but there is no evidence to show that a truly creeping-rooted plant will not spread in certain climates or on certain soil types. Spreading of plants will occur in pots in the greenhouse as well as in the fields on sandy or clay soils. Rhizomatous spreading plants, on the other hand, will frequently not creep at all under very dry climatic conditions. VIII. The Future of Spreading Alfalfas
Investigational work indicates that spreading alfalfas have a bright future in making the alfalfa crop even more useful than it is today. Although the idea that the creeping habit offers the greatest possibilities in improving the attributes of the crop for pasture ( Aamodt, 1952; Heinrichs, 1954; Graumann, 1958) is sound, there is no doubt that the character can also add a great deal of usefulness to the hay crop. The selfrejuvenation ability of a creeping type after winter injury, heaving, or drought damage should be as important in a hay crop as in a pasture crop. The breeding work done in Canada, the United States, and Australia clearly indicates that the creeping-root character can be transferred from low yielding, poor seed-setting types of plants to high-producing types. The breeding programs which have progressed beyond the second generation indicate that the creeping character often becomes more pronounced in these later generations than was the case in the creepingrooted parental type. It appears that for maximum expression the character must become genetically associated with the growth vigor inherent in alfalfa varieties adapted to any particular environment. In spite of the wide possibilities that seem to be ahead for the creeping character in alfalfa, it should be stressed that the plant breeder perhaps should concentrate his efforts on developing a pasture type because this is where the greatest need lies. It is the vast dry ranges of so many countries that are crying out for a legume that will increase and stabilize production. Persistence as a requirement in the alfalfa variety should be stressed and restressed. It is so easy to stray away from this requirement because most plant breeders and agronomists use yield as
336
D. H. HEINRICHS
the ultimate yardstick rather than persistence. E. R. Jackman, Soil Conservationist in Oregon, in a recent letter to the writer, said that research persons tend to have a “yield complex and somehow cannot see that persistence comes first. Many will agree that this is generally true. However, it is not necessarily the plant breeder‘s fault, but perhaps just as much the fault of the agronomist, rangeman, or farmer, who often are slow to accept and get new varieties into use where they should be used. The great need in the future will be the proper evaluation of creepingrooted and rhizomatous alfalfas in relation to varieties of similar adaptivity without the spreading habit. This is the area in which much more research needs to be done before a true assessment of the value of the spreading habit of growth will be forthcoming. Research work on the various types of creepers on an individual plant basis requires investigation before the plant breeder will know exactly the type for which he is selecting. The only detailed investigation of this nature was done by Murray (1955). She found that the rate of spreading varied greatly between creeping-rooted clones. There are sparse creepers and dense creepers and all gradations between. Which type to select for will depend on where and how the alfalfa is to be used. Certainly the agronomic possibilities are great indeed. The term creeping alfalfa would be best not used as a synonym for grazing alfalfa because the two have distinct and different meanings. Nevertheless, it seems logical to suppose that the creeping-root character will make a good grazing alfalfa even better. REFERENCES Aamodt, 0. S. 1952. What’s N e w In Crops Soils 5. Adams, M. W. 1959. J. Genet. 56, 395-400. Adams, M. W., and Semeniuk, G. 1958. S . Dakota State Coll. Agr. Expt. Sta. Bull. 469. Burlingham, E. F. & Sons. Forest Grove, Oregon. Nomad Alfalfa. Camahan, H. L. 1959. Agron. J. 51, 625626. Clark, K. W. 1960. Rept. 17th Alfalfa Imp. Conf. pp. 99-106. Daday, H. 1962. Australian J . Agr. Res. 13, 813-820. Daday, H., Mottershead, B. E., and Rogers, V. E. 1961. Australian J . Exptl. Agr. Animal Husbandy 1, 67-72. Dudley, J. W., and Hanson, C. H. 1961. Crop Sci. 1, 59-63. Edye, L. A., Haydock, K. P., and Saunders, A. M. 1961. Conf. Cereal Pasture Plant Breeders C.S.I.R.O. Canberra Australb 1, 31-1-31-9. Gamer, S. 1922. U.S. Dept. Agr. Bull. 1087. Graumann, H. 0. 1955. Soil Conseru. 21, 103-104. Graumann, H. 0. 1958. What’s New Crops Soils 10. Hansen, N. E. 1909. U.S. Dept. Agr. Bull. 150. Hansen, N. E. 1927. S . Dakota State Coll. Agr. Erpt. Sta. Bull. 224.
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Hanson, C. H., Garrison, C. S., and Graumann, H. 0. 1960. US. Dept. Agr. Agr. Handbook 177. Heinrichs, D. H. 1950. Rept. 12th Alfalfa Imp. Conf. pp. 59-61. Heinrichs, D. H. 1954. Can. J. Agr. Scl. 34,269-280. Heinrichs, D.H. 1958. Agr. Inst. Reu. May-June. Heinrichs, D. H. 1959. Can. J. Plant Sci. 39, 384-394. Heinrichs, D. H. 1962. Rep. 18th Alfalfa Imprwement Conf., Daois, Calif., pp.
45-50.
Heinrichs, D. Heinrichs, D. Heinrichs, D. Heinrichs, D.
H., and Bolton, J. L. 1958. Can. Dept. Agr. Publ. 1030. H., and Morley, F. H. W. 1960. Can. 1. Plant Sci. 40,487-489. H., and Morley, F. H. W. 1962. Can. J. Genet. Cytol. 4, 79-89. H., Troelsen, J. E., and Clark, K. W. 1960. Can. J . Plant Sci. 40,
638-644.
Jones, A., and Hanson, C. H. 1959. Agron. J. 51, 710-718. Komarov, V. L. 1945. Flora URSR 11, 129-176. Ludwig, L. J. 1960. M.S.Dissertation, University of New Zealand. Morley, F. H. W., and Heinrichs, D. H. 1960. Can. 1. Plant Sci. 40,424-433. Morley, F. H. W., Daday, H., and Peak, J. W. 1957. Australian J. Agr. Res. 8,
635-651.
Murray, B. E. 1955. Ph.D. Dissertation, Cornell Univ., Ithaca, New York. Murray, B. E. 1957. Can. J. Botany 35, 463-475. Nilan, R. A. 1951. Sct. Agr. 31, 123-127. Oakley, R. A,,and Carver, S. 1913. US. Dept. Agr. Bur. Plant Ind. Circ. 115. Oakley, R. A., and Garver, S. 1917. U.S. Dept. Agr. Bull. 428. Odland, T. E., and Skogley, C. R. 1953. Agron. J. 45, 243-245. Oliver, G. W. 1913. U.S. Dept. Agr. Bur. Plant Ind. Bull. 258. Palmer, T. P. 1959. New Zealand J . Agr. Res. 2, 1195-1202. Rogers, V. E. 1961. Australtan J. Exptl. Agr. Animal Husbandry 1, 80-66. Smith, D. 1950. Agron. J. 42, 398-401. Smith, D. 1951. Agron. J . 43, 573-575. Smith, D. 1955. Agron. 1. 47, 588-589. Southworth, W. 1921. Scl. Agr. 1, 5-9.