Biodiversity for industrial crop development in the United States

INDUSTRIALCROPS ANDPRODUCTS ANINTERNATIONALJOURNAL

Industrial Crops and Products 2 (1994) 259-272

ELSEVIER

Biodiversity for industrial crop development in the United States G.A. White av*,J.C. Gardner b, C.G. Cook” 0 USDA-ARS, National Germplasm ResourcesLaboratory,BeltsvilleAgriculturalResearch Center, Beltsville,MD 20705, USA b Canington Research Extension Centel;North Dakota State University,Box 219, Carriqton, ND 58421, USA c USDA-ARS, PO. Box 267, 2413 E. Hny. 83, Weslaco,TX 78596, USA

Received 9 January 1994; accepted 21 March 1994

Abstract

Genetic diversity is an essential component of successful improvement programs worldwide for conventional and potential new crops. Access to diverse genetic materials is often the key factor in the success or failure of new industrial crops, all of which have deficiencies in useful constituents and/or agronomic traits. Crambe (Crambe abyssinica) was first identified as a source of erucic fatty acid in 1957. Farmers, mainly in North Dakota, planted 24,300 ha of crambe in 1993. Although five cultivars have been developed, limited genetic diversity in this species has resulted in slow, incremental improvements. Kenaf (Hibiscus cannabinus), an annual source of paper pulp and other fibrous products, remains on the verge of significant commercialization. Most of the standard cultivars trace back to a Salvadorian strain. Improvements in adaptability and nematode resistance would enhance the crop prospects for kenaf. The development of nematode-resistant/tolerant cultivars may require intensive evaluation of materials with nematode tolerance, interspecific crosses with bridging species, or the use of biotech techniques. For Cuphea, the development of lines that retain seeds in their fruit and a significant broadening of the species germplasm base represents major advances in the search for annual crop sources of medium-chain-length fatty acids. Several species, especially Euphorbia lagascae, Stokesia laevis, and Vemonia galamensis, are potential new oilseed sources of epoxy fatty acid. Germplasm of E. fagascae is very limited but is essential in improving seed retention. Germplasm of S. laevis, native to the United States, is readily accessible and genetically variable. The slow germination and seedling growth of this perennial are major deterrents to its commercialization. The day-length neutral selections of K galamensis have greatly improved the crop potential of this African species. Future prospects for acreage expansion of crambe and kenaf appear very good and the crop potential of Cuphea has been greatly enhanced through significant agronomic improvements. The successful commercialization and sustained production of these and other species depend to a large degree on access to genetically diverse germplasm. Free exchange of germplasm internationally will contribute significantly to the worldwide development of new industrial crops. Keywords: New crops; Crambe; Cuphea; Stokes aster; timonia; Euphorbia; Medium-chain fatty acids; Epoxy fatty acids; Genetic diversity; Crop production

1. Introduction

Genetic diversity, an important component of any crop improvement program, is critical for de* Corresponding author.

veloping

new industrial

crops.

Rarely

can a plant

species be taken from the wild and converted to a commercial crop without considerable manipulation of their genetic resources. Lack of access to adequate genetic diversity in the past has significantly delayed the development of a

0926-6690/94/$07.00 8 1994 Elsevier Science B.V. All rights reserved. SSDI 0926-6690(94)00008-M

Erucic acid; Pulp; Fiber products;

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G.A.

Whiteet al. I Industrial Crops and Products 2 (1994) 259-272

number of new industrial crops in the United States. Scientists of the Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA), initiated an ambitious screening program in 1957 to identify plant species that contained potentially useful constituents. Chemists teamed with botanists to examine seeds of 6355 species for oils and fatty acids and to evaluate 506 species as fiber sources during the 1957-1976 period (Printen, 1977). These efforts uncovered many promising leads, in fact too many to pursue vigorously with the limited research funding available. Those species with the best constituent-use potential and favorable botanical attributes were subjected to preliminary evaluation by Federal and State agronomists and plant breeders. Species of several genera, including Crambe (Fig. l), Cupheu, Hibiscus, Lesquerella, and Wnonia emerged as top candidates for advanced development. At present, research on these genera includes breeding, cultural practices, germplasm assemblage and evaluation, processing, product development, and commercial promotion. In this paper, we focus on the commercialization, research, and genetic resource status of

crambe (Crambe abyssinica Hochst. ex R.E. Fries), kenaf (Hibiscus cannabinus L.), Cuphea species, and three sources of natural epoxy acid seed oils. Harsch (1993) describes new industrial uses and new markets for crambe and kenaf. 2. Crambe 2.1. Background Seed of C. abyssinica was first introduced into the United States in the 1940’s by the Connecticut Agricultural Experiment Station (White and Higgins, 1966). Later in 1957, this species was identified as having a high content of erucic fatty acid in the seed oil and high protein levels in the seed meal. Erucic acid, a mono-unsaturated longchain fatty acid containing 22 carbons, has utility in polymers, lubricants, and plasticizers (Princen, 1977). A 1958 Swedish introduction, PI 247310 (plant introduction number), was the main seed source for field studies until 1962 (White and Higgins, 1966). Additional germplasm was introduced mainly from Europe for more extensive field trials and initiation of breeding efforts. Lessman (1975) described the development of the three

Fig. 1. Flowering and fruiting branches of Crambe abyssinica. Fruits are one-seeded.

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cultivars Prophet, Indy, and Meyer, which were released by the Purdue University Agricultural Experiment Station in 1968, 1969, and 1973, respectively. Later, Campbell et al. (1986a, b) released BelAnn and BelEnzian plus three germplasms. Experimental plantings of Crambe have been made in many states for more than 20 years (White and Higgins, 1966; Anonymous, 1993). 2.2. Commercialization Commercialization of crambe in North Dakota has been very successful (Gardner et al., 1991, 1992, 1993). Cultivated area and seed yields for 1990-1993 in North Dakota and other states are given in Table 1. National Sun Industries (NSI), an oilseed processing company, contracted with farmers for all of the North Dakota acreage. The oil has been mostly marketed domestically for use in slip and antiblock agents for plastic wrap and bags. Minor amounts of oil have gone into cosmetic products and some have been exported to Europe. The meal has been sold as a high-protein meal for finishing beef cattle. Small plantings were made in 1993 in Kansas and Colorado as possible production areas for a NSI-retrofitted oilseed processing facility near Goodland, Kansas. About 608 ha of the 27,470 ha of crambe in North Dakota were devoted to seed production of the cultivars Meyer, BelAnn, and BelEnzian. Because of greater disease incidence during the wetter than usual 1993 season, seed quality up-

Table 1 Crambe production and seed yields during 1990-1993 Area

1990

1991

1992

1993

9,552 1,456

1,812 1,498

8,530 1,215

22,410 1,232

North Dakota

Hectares Seed yield (kg/ha)

grading may limit the 1994 potential production to about 30,375 ha. However, the estimated contracted area planned by NSI for 1994 is 24,300 ha solely in North Dakota. 2.3. Germplasm diversity The U.S. collection of crambe germplasm is maintained at the North Central Regional Plant Introduction Station, Ames, Iowa, and consists of thirteen species (Thompson et al., 1992). Only those species in the Section Leptocrambe have high amounts of erucic acid in their seed oils. The number of accessions of this Section represented in the collection and the gametic chromosome numbers are given in Table 2. In addition to the C. abyssinica accessions in the collection, approximately 1100 breeding lines from the former program of K.J. Lessman, Las Cruces, New Mexico, are being utilized at North Dakota State University, Fargo (Hanzel et al., 1993). Several of the better New Mexico lines have been tested at different locations. NM2 has performed well and is being documented for release. Genotypic and phenotypic variations in crambe are rather limited, thus only incremental progress has been made in cultivar improvement. Large numbers of selections are being evaluated followed by hybridization of superior lines. These crosses should expand the genetic diversity of C. abyssinica and allow improvements in yield, oil quality and agronomic traits such as maturity, height, and seed retention. Also, major efforts will be directed to identify low glucosinolate materiTable 2 Number of Crambe accessions (Section Leptocrambe), in the National Plant Germplasm System (NPGS) and their ploidy levels Species

Number of accessions

Ploidy level

Crambe abyssinica C. jilifomis Jacq. C. hispanica L. var. hispanica C. hispanica var. glabrata C. kralikii Cosson

330

45a

High Plains

-

Hectares Seed yield (kg/ha) San Luis K&y,

972 616

Colorado

Hectares Seed yield (kg/ha) Total hectares

972 2,688 9,552

1,812

8,530

24,414

261

a After Leppik and White (1975). b After White and Solt (1978).

(n)

25

15a

62 27

3oa 15b

11

15,30,45 b

262

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als which, if found and incorporated into superior cultivars, would enhance meal quality. The variable ploidy levels of related species could prove useful for creating a wide range of variability for long-term crop improvement. An interesting option is C. kralikii with its three ploidy levels (White and Solt, 1978). Perhaps greater cold and drought tolerance could be transferred into C. abyssinica from C. kralikii. Since only one accession of C. kralikii has a gametic number of 45, additional germplasm from Algeria should be collected and tested for ploidy level. Another potentially interesting objective would be to try to genetically 8x two- or three-seeded fruits which might make combine dehulling feasible. These multi-seeded fruits occur naturally in very low percentages in seedlots. Other areas of research include seed dormancy, proper planting rates, dates and depth, and timing of swathing and direct combine harvest. For continued acreage expansion, new market outlets involving different uses are needed. The lubricant market, especially targeted to replace petroleum in sensitive environments like timber and marine applications, looks promising. Also, the high erucic oil of crambe might displace other oils in surfactant and nylon production. There are many other potential uses for erucic acid and its derivatives (Carlson and Van Dyne, 1992; Sonntag, 1992). The future of crambe as an industrial crop for the United States looks bright; however, crop improvement through expanded genetic resources, use of genetic variability, and the expansion of seed oil markets are required for crop stability and acreage increase. 3. Kenaf 3.1. Background Kenaf (Hibiscus cannabinus L.) and its close relative roselle (H sabdatifa L.) are ancient crops that have been cultivated for many years as sources of cordage fiber for rope, twine, and burlap. Most recently, the major production for the stem bast fibers has been concentrated in India, Thailand, China, Taiwan, the former

Soviet Union, Iran, Mozambique, Ivory Coast, Guatemala, and El Salvador (Anonymous, 1993). Excellent yields of kenaf are obtainable in the lower Rio Grande Valley of Texas (Fig. 2) and in other areas of the United States. During World War II, U.S. officials became concerned about the possible disruption of foreign sources of cordage. This concern led to the organization of several cooperative research projects among the United States, Cuba, and Guatemala. A research team in Florida conducted various studies on kenaf production, breeding/genetic improvement, pathology, harvesting, and equipment development. Subsequently, two kenaf cultivars Everglades 41 and Everglades 71 were released (Wilson et al., 1965). In the early 1960’s, interest in kenaf as an annually renewable source for paper pulp resulted in experimental trials scattered across the U.S., especially the South and Midwest (White et al., 1970). The Everglades, Cuban and Guatemalan cultivars formed the basis for these field trials. Unfortunately, by this time the Florida team effort on kenaf as a cordage source had been closed out. If the research had been continued with redirection from cordage to paper pulp, the U.S. could possibly have commercialized kenaf. Breeding efforts that were initiated in Savannah, Georgia, were brief because of limited funding. However, the release of four kenaf germplasm lines with moderate root-knot nematode resistance and five lines of fiber-type roselle did result from the Georgia project (Adamson, 1983). Recent renewed national interest in alternative crops has provided funding of projects in Mississippi, Oklahoma, and Texas. Even during the period when funds were unavailable, USDA scientists still provided materials (seed samples) and technical information covering production, processing, and end uses of the fiber. The prospects for the building of a sizeable pulp mill to process kenaf in south Texas created further interest in this crop. 3.2. Commercialization Currently, interest in cultivating kenaf is centered in Texas, Mississippi, Louisiana, California, and Oklahoma. Researchers (Malone et al., 1990; Brake et al., 1993) found that the woody core was

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263

Fig. 2. An excellent crop of kenaf cv. Everglades 71 in the lower Rio Grande Valley of Texas.

comparable to pine sawdust as broiler litter. According to a report by USDA’s Economic Research Service (Anonymous, 1993), 1700 ha of kenaf were harvested in 1992 and 1700 ha were planted to kenaf in 1993 (Table 3). European interest in kenaf resulted in the 1993 production of approximately 2025 ha, mostly in Italy. Earlier research was directed toward the use of whole kenaf stems for various pulp products such as paper, newsprint, paper board, and pressed

wood. Similar applications were envisioned if the core and bast fibers were mechanically separated, recombined in different proportions, or blended with wood fibers. Furthermore, additional nonpulp uses now include forage, poultry litter, animal bedding, mulches, mushroom compost, seeding and erosion control mats, oil absorbent, fiberglass substitute, and potting mixes. Natural Fibers of Louisiana, Inc. with its fiber separation facility, sells the fiber components as oil

264

G.A. White et al. I Industrial Crops and Products 2 (1994) 259-272

Table 3 Kenaf plantings (ha) in the United States, 1992-1993 B State

1992

1993

California Louisiana Mississippi New Mexico Tzxas Other

226 122 1134 20 195

226 105 810 82 486 60

Total

1697

1769

a After Anonymous, 1993.

absorbents, mulches, horse bedding and chicken litter, potting media, mats, and other products (H. Willett, pers. commun., 1993). This company is also looking at kenaf fiber components as substitutes for fiberglass. Kenaf production in Louisiana under farmer contracts fits in rotational cropping with sugarcane. A modified sugarcane harvester is used to harvest the 1.7 m wide rows of kenaf (Fig. 3). Stems are allowed to field dry and are then stacked to await mechanical fiber separation.

Approximately 122 ha of kenaf were grown in 1992 and 1993. According to Willett, an expansion to about 486 ha acres in 1994 and perhaps to 730 ha in 1995 is anticipated. Nematodes have not posed a problem. The main cultivars used are Everglades 41 and Everglades 71. Three other companies (Anonymous, 1993) also operate fiber separation facilities and generally compete for the same market outlets; however, because of their locations, they can exploit certain product markets. For example, AgroFibers, Inc. of California sells bast fibers for highgrade pulp and packing materials, and the woody core for animal bedding and potting mixes. This company also plans to manufacture wildflower and erosion-control mats. 3.3. Genetic diversity Cooperative research on kenaf among the U.S., Cuba and Guatamala resulted in the development of a number of useful cultivars. These cultivars were selected and developed from a highly variable Salvadorian strain. They differed in leaf

Fig. 3. Harvesting of kenaf with a modified sugarcane harvester in the lower Rio Grande Valley, Texas.

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265

Fig. 4. Kenaf roots: (1) healthy, (2) galled by root-knot nematodes, (3) galled with root-rot complex involving soil-borne fungi.

shape, photoperiod response, and dry stem yields. The Belle Glade, Florida program developed Everglades 41 and Everglades 71, the most widely used cultivars in U.S. research. Germplasm from Africa, China, India, Russia, Taiwan, and other countries have been added to the U.S. collection over the years. Tainung No. 1 and Tainung No. 2 from Taiwan are very productive, environmentally stable cultivars. The most production-limiting pest of kenaf is root-knot nematodes, especially the southern organism [Meloidogyne incognita (Kofoid and White) Chitwood]. A root-rot complex involving soil-borne fungal pathogens is often associated with nematode damage (Fig. 4). Although several fiber-type roselle cultivars are resistant to nematode attack, their stem yields are well below kenaf yields under nematode-free conditions (Scott et al., 1993). Approaches to solving the nematode and soilborne fungi complex include intensive evaluation of superior agronomic cultivars and breeding lines for genetic resistance/tolerance, evaluation of wild types from Africa, and attempting to transfer re-

sistance from roselle. Cook et al. (1993a, b) have identified two lines (45-9 and 19-117-2) of kenaf that have significant levels of field tolerance to root-knot nematodes and have produced good stem yields on different soil types and environmental conditions. In addition, a greenhouse study by Mullin et al. (1994) identified a kenaf selection, A131-91, with more tolerance to root-knot nematodes than 45-9, 19-117-2, and Everglades 71. Germplasm with improved resistance to charcoal rot fungus [Macrophomina phaseolina(Tassi) Gold.] has been identified (Cook, 1993). The continued use of genetic diversity will include evaluation of recently introduced germplasm from China and the International Jute Organization (Bangladesh) for yield and resistance/tolerance to nematodes, pathogens and environmental adversities. Other emphases will include improvement of seed quality and crop rotation strategies to improve yield and reduce losses resulting from the root-knot nematode/soil-borne fungi complex.

266

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Fig. 5. (A) Seeds of Cuphea exposed to shattering. (B) Seed retention of Cuphea hybrid selection with closed, intact, maturing fruits along a fruiting branch. (Photographs by S.J. Knapp, Oregon State University.)

4. Cuphea 4.1. Background According to Kleiman (1990) and Knapp (1990), the U.S. annually imports about 454 million kg of medium chain-length fatty acids derived from coconut and palm kernel oil for use in soaps and detergents. Species of the genus Cuphea are rich sources of medium-chain triglycerides with caprylic, capric, lauric or myristic acid composing major percentages in their seed oils (Miller et al., 1964; Kleiman, 1990). In the early phases of new crop screening, Cuphea was recognized as having potentially valuable seed oil composition; but because of poor botanical traits, especially excessive seed shat-

tering (Fig. 5A), the genus was not actively pursued in agronomic evaluations. Likewise, the germplasm collection at that time was extremely limited. 4.2. Genetic diversity Prompted by commercial interest, increased efforts began in 1981 to expand the Cuphea germplasm collection and accelerate its evaluation (Thompson et al., 1992). Distribution of the estimated 250 to 260 species ranges from the United States and Mexico southward into Brazil. The current collection is comprised of 829 accessions including 89 species, one subspecies, two hybrids, six botanical varieties, and seven unidentified species. W.W. Roath and M.F! Widrlechner

G.A. White et al. /Industrial Crops and Products 2 (1994) 259-272

(pers. commun., 1993) collected 31 additional accessions of Cuphea in Mexico during SeptemberOctober, 1993. Five species were collected including 20 seed samples of C. lanceolata, the main target species of the exploration. Several species of Cuphea offer potential as omamentals. Cuphea ignea, the firecracker or cigar plant, has been available as an ornamental for several decades. Jaworski and Phatak (1990) identified three superior selections of C. glutinosa from 250 plants representing four introductions. They subsequently released all three selections (Jaworski and Phatak, 1991a, 1992). These two researchers also released an ornamental selection of C. llavea (Jaworski and Phatak, 1991b). S.J. Knapp (pers. commun., 1993) has just released Plant Introduction (PI) number 574384 (LN-183), a fully nondormant, open pollinated population of C. Zanceolata, and five autogamous hybrid lines from crosses of C. viscosissima x C. lanceolata f. silenoides (PIs 574491-5). Over a short period of time, Knapp (1990, 1993) and collaborators have devised effective breeding strategies for Cuphea that have resulted in remarkable advances. Although working with a large number of species spreads resources thinly,

261

eight species initially were investigated, with emphasis on the best sources of capric and lauric acid. These species did not differ with respect to seed retention and the lack of adequate germplasm hampered progress. Other traits such as seed dormancy, seed yield, and mode of pollination (autogamous vs. allogamous) also were included. Simultaneous selection for these traits ensued. In 1988, C. lanceolata and C. viscosissima were emphasized for research because of their various desirable traits of the two species plus the discovery that fertile interspecific hybrids occurred naturally between them. Additionally, germplasm accessibility in Mexico and the United States is relatively easy (Fig. 6). While selection for higher oil content within the two species has occurred, this effort shifted to the hybrid C. viscosissima x C. lanceolata f. silenoides population VL-119. Cuphea lanceolata provides non-dormant types, whereas C. viscosissima provides autogamous reproduction and good seed productivity. Unexpectedly, hybrid population VL-119 provided excellent seed retention (Fig. 5B). Intermating within VL199 led to 15 seed retaining phenotypes from 500 spaced plants. Several of the 15 phenotypes are quite promising for further development and pos-

Fig. 6. Wild distribution of Cuphea lanceolata and C. viscosksima.

268

G.A. Whiteet al.IIndustrialCropsand Products2 (1994) 259-272

Fig. 7. Direct combining of a good seed retaining selection of Cuphea hybrid from population VL-119. (Photo by S.J. Knwb Oregon State University.)

sible release. Combine-harvesting with minimal seed loss of one of the superior seed retaining lines was accomplished (Fig. 7). Other researchers found limited morphological differences among 40 accessions of C. viscosissima, and the variation in seed shattering was considered insufficient for exploitation (Roath et al., 1992). The percentage range for every fatty acid in C. viscosissima was narrow and the seed oil percentages ranged from 27.3% to 33.4% (Knapp et al., 1991). 4.3. Commercialization What are the key criteria for commercial acceptance of developed Cuphea cultivars? Obviously the crop must yield sufficient seed and oil to be profitable to the growers, processors, and end users. Selection and further breeding are required to achieve high seed and oil yields, nondormant seed, shatter resistance, and autofertility. All of these traits are accessible in Cuphea germplasm and their introgression into excellent cultivars seems probable within a few years.

The preceding is a brief account of exciting progress toward the commercialization of Cuphea as a new industrial oilseed source of medium chain-length fatty acids. Innovative research, infusion of a much broader range of germplasm, and the creation and evaluation of genetic variability through interspecific crosses have made this progress possible. Cuphea is a variable genus with many species and considerably within-species diversity. Several of the better materials originating from the Oregon State University program will be registered with the Crop Science Society of America and some may be protected through the Plant Variety Protection Office of the U.S. These lines should be available to researchers from the developer. While seed oils of the vastly improved lines are high in capric acid, lauric acid makes up the majority of the imported coconut and palm oils. Knapp (1992) believes that the genetic variability and the technology are available that will allow the tailoring of seed oil composition in superior agronomic types to meet market needs. The availability of various medium chain-length fatty acids through

G.A. White et al. /Industrial Crops and Products 2 (1994) 259-272

annually renewable resources should open up new market vistas. 5. Epoxy acid seed oil sources While the U.S. consumes about 63,560,OOOkg (Princen, 1977) of epoxy fatty acids annually, there are no U.S. sources of naturally occurring epoxy fatty acids. Three species, Euphorbia lagascae Spreng., Stokes aster [Stokesia laevis Hill (Greene)], and Vemonia galamensis (Cass.) Less. are excellent potential new oilseed crop sources of vernolic acid (12,13-epoxy-cis-9-octadecenoic). These oils should have good market outlets for use in plastics, paints, and lubricants. The germplasm status for these three species is summarized in Table 4. United States needs are now met by epoxidation of fats, and linseed and soybean oils. 5.1. E. lagascae

This plant was evaluated in preliminary trials in the 1960’s because of its high seed oil content and desirable upright plant structure. Knapp (1990) states that seed shattering and seed dormancy usually determine the difference between undomesticated and domesticated forms of a species. This statement adequately applies to E. Zagascae Table 4 Germplasm status for Euphorbia lagascae, Stokesia laevis, and Vernonia galamensis a

Species

Number of accessions

Origin

E. lagascae

5 40 13 9

Spain U.S. Africa Africa Africa

S. laevis K galamensis subsp. afromontana subsp. galamensis var. australis var. ethiopica var. galamensis var. petitiana subsp. gibbosa subsp. lushotoensis subsp. mutomoensis subsp. nairobiensis

18

1 4 5 3 4 2 6

a Accessions maintained at seedbanks Plant Germplasm System.

Africa Africa Africa Africa within the National

269

with its seed dispersal mechanism. Because of the lack of seed retention and limited germplasm, this species was dropped from the evaluation program. Interest in this species has been renewed because of increased recent support of new crop research and added germplasm from Spain. Pascual-Villalobos et al. (1993) have identified indehiscent phenotypes through mutation breeding. By improving seed retention, the potential for commercializing this crop is considered excellent. 5.2. S. laevis Currently, there is no crop development research on Stokes’ aster. Its potential as a source of seed oil high in epoxy acid has been discussed (White, 1977; Campbell, 1981; Shands and White, 1990; Knapp, 1990). The senior author participated with J.E. Bear in a 1973 field exploration for S. laevis. Subsequently, the various accessions were increased in isolation at the Beltsville Agricultural Research Center. This collection is highly diverse genetically relative to seed retention (Fig. S), productivity, plant habit, and flowering/maturity dates. Campbell (1989) released four germplasm lines in which he utilized selected plants from 16 germplasm accessions. These germplasm lines were developed for improved seed yield, seed retention, and seedling and general vigor through intercrosses and recurrent selection. Although seed and plants are commercially available as ornamentals, this limited commercial outlet could be greatly expanded through selection and evaluation. As an oilseed crop, disadvantages at present include slow germination and seedling development and allofertility. S. laevis is a perennial, which could be considered an advantage for sustainable agriculture, but no multi-year management studies have been conducted. There are relatively few accessions in the NPGS germplasm collection, but the wild populations are quite accessible and diverse. Unfortunately, some of the smaller populations are near extinction. Campbell (1981) reported variation in seed oil (27.040.0%) and vernolic acid content (63.1-78.8%). White (1977) observed oil content up to 44% in 20 germplasm accessions.

270

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Fig. 8. Seed heads of Stokesia laeviswith inflexed bracts that contribute to seed retention.

5.3. Vemoniu galamensis Gunstone (1954) discovered that the seed oil of K anthelmintica contained high amounts of the epoxy fatty acid now referred to as vemolit acid. Breeding and cultural research aimed at assessing the crop potential of this species ended when no genetic variability for seed retention could be identified in the limited available germplasm. Perdue et al. (1986) found a Vernonia species in Ethiopia that had good seed retention. Initially, this new introduction was designated as v pauciflora but was later identified as K galamensis subsp. galamensis var. ethiopica. Oil content of Kgalamensis was higher than the highest values reported for K anthelmintica. This acces-

sion was daylength sensitive (short day) and, thus would not set seed in the continental U.S. The presence of good seed retention and favorable utilization research on seeds produced in Zimbabwe re-stimulated interest again in Vemonia. This led to the introduction of more accessions of K galamensis from Africa. The staff of the USDA-ARS research facility at Phoenix, Arizona, and state cooperators identified day-neutral plants within K galamensis subsp. galamensis var. petitiuna (Thompson et al., 1992). Intensive selection is underway, including hybridizing among subspecies and obtaining favorable recombinations (Dierig and Thompson, 1993). Selections from hybrids of K galamens& subsp. galamensis var. petitiana (A20295) x (V. galamensis subsp. galamensis var. ethiopicu (PI 312852) are the foci for identifying superior autofertile, day-neutral, good seed retention, non-dormant and high yielding (seed and oil) types. Several generations of these selections have been produced and are being widely evaluated throughout the United States. Good progress has been achieved in producing lines with favorable agronomic characteristics. Thompson et al. (1992) and Dierig and Thompson (1993) described the germplasm collection of K galamensis and its use. There are 65 accessions of Kgalamensis in the germplasm collection in Iowa plus different accessions under study in Phoenix. The collection includes six subspecies and four botanical varieties of Kgalamensis subsp. galamensis. Additional germplasm of K galamensis and especially Kgalamensis var. petitiana and var. ethiopica would be desirable for breeding the genetic base of day-length neutrality. Pollinations under controlled day lengths probably can serve to transfer desirable traits from short-day selections into day-neutral types. Acknowledgements Y The authors express their appreciation to S.J. Knapp for information and photographs, to Vicki M. Binstock for slide and manuscript preparation, to reviewers T.A. Campbell, K.D. Carlson and A.E. Thompson, and to others who contributed information and/or editorial assistance.

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