Growth and mineral nutrition of pear rootstocks in lime soils

Scientia Horticulturae, 54 ( 1993 ) 13-22

13

Elsevier Science Publishers B.V., Amsterdam

Growth and mineral nutrition of pear rootstocks in lime soils M. Tagliavini, D. Bassi and B. Marangoni Istituto di Coltivazioni Arboree, University of Bologna, Bologna, Italy (Accepted 6 November 1993 )

ABSTRACT Tagliavini, M., Bassi, D. and Marangoni, B., 1993. Growth and mineral nutrition of pear rootstocks in lime soils. Scientia Hortic.,54:13-22. Little information is available on the tolerance of pear rootstocks to lime-induced iron chlorosis. I n a 2-year study, micropropagated plants of the pear rootstocks OH × F 51, OH × F 333, B 21, C 106 and D 50, and Adams quihce were grown in low calcareous soil (LC, 1.6% lime) and high calcareous soil (HC, 72.9% lime) as well as in a mixture of HC:LC (50:50, w:w) (M 1 ) at 33.8°/o lime content and a mixture of HC:LC (75:25, w:w) (M2) at 48.3% lime content. By the end of Year 2, O H × F 51, B 21 and C 106 had reduced dry matter accumulation in stem and roots in HC soil only; the other rootstocks were adversely affected by lower soil-lime contents. Only Adams decreased the shoot-toroot dry weight ratio in relation to increased soil lime. Leaf chlorotic symptoms of plants grown under increasing lime were most severe in OH X F 333, D 50 and Adams. Root Ca concentration increased linearly and root iron and manganese decreased linearly at increasing soil lime rates. Root Cu concentration increased linearly with soil Cu content, the latter being ten-fold higher in HC than LC soil. These findings indicate varying susceptibility of pear rootstocks to lime-induced iron chlorosis. Rootstock tolerance is a necessary condition in order to overcome lime-induced iron chlorosis in pear cultivars. In grafted trees it is, however, possible that mechanisms other than iron uptake are involved in leaf chiorosis. Keywords: Copper; Cydonia oblonga; leaf chlorosis; manganese; Pyrus communis; root calcium; root iron; soil lime. Abbreviations: CPI=chlorotic power index; H C = h i g h calcareous soil; LC=low calcareous soil; M l = mixture of HC:LC (50: 50, w:w); M2 = mixture of H C : L C (75:25, w:w).

INTRODUCTION

In Italy, many pear orchards are planted in alkaline and calcareous soils. Quince rootstocks have been largely used in the Italian pear industry for their early bearing and dwarfing aptitude (Baldini, 1953 ). However, as compared Correspondence to: Massimo Tagliavini, Istituto di Coltivazioni Arboree, Via F. Re 6, 40126 Bologna, Italy.

© 1993 Elsevier Science Publishers B.V. All rights reserved 0304-4238/93/$06.00

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M. TAGLIAVINIET AL.

with pear seedlings, quince rootstocks enhance pear scion susceptibility to lime-induced iron chlorosis, although several quince rootstock clones provide varying tolerance levels to calcareous soils (Viti and Cinelli, 1989). Several clones of Pyrus communis have recently been proposed as more appropriate rootstocks to increase cold hardiness and compatibility. Nevertheless, information on their tolerance to lime-induced chlorosis is largely incomplete (Michelesi, 1991 ). Iron deficiency has been reviewed by Chen and Barak ( 1982 ) and Korcak (1987). Chaney and Bell (1987) stressed the interactions between Fe-poor soil and plant strategies to obtain iron from the root environment, including changes in mineral uptake. Although soil HCO~- reduces iron uptake (Marshner, 1986), chlorotic pear leaves show a total Fe content similar to green ones. This fact suggests that mechanisms other than iron uptake are also involved in lime-induced iron chlorosis (Kolesch et al., 1987 b). The objectives of the present study were to evaluate the growth response of several pear rootstocks to increasing levels of total soil CaCO3 and to analyse the mineral composition of pear and quince trees in soils with increasing levels of total lime. MATERIAL A N D M E T H O D S

One-year-old micropropagated plants of pear (P. communis, L. ) rootstocks O H × F 51, O H × F 333 (Brooks, 1984), B 21, C 106 and D 50 (Bassi et al., 1989 ) and the Adams quince (Cydonia oblonga, L. ) rootstock were individually transplanted during winter 1988-1989 in 2-1 pots containing the following media (Table 1 ): low calcareous soil (LC) with 1.6% total CaCO3, texture fraction, 55% sand, 18% silt and 27% clay; high calcareous soil (HC) with 72.9% total CaCO3, texture fraction, 50% sand, 23% silt and 27% clay; mixture of LC and HC soil (50: 50, w:w) (M1); mixture of LC and HC soil ( 75: 25, w: w ) (M2). LC and HC soils were mixed to create four CaCO3levTABLE 1 Total carbonate (CaC03) , active lime (AL), chlorotic power index (CPI), pH and micronutrient concentrations of soils Soil

CaCO3 (%)

AL (%)

CPI (ppm) ~

pH (ppm) l

Fe (ppm)'

Cu (ppm) ~

Zn (ppm) ~

LC M1 M2 HC

1.6±0.42 33.8±2.8 48.3±1.1 72.9±4.8

1.0±0.6 9.9±0.1 11.4±0.6 12.0±0.1

53 463 535 1948

8.2 8.2 8.2 8.2

13.7±0.5 15.2±l~9 14.6±5.0 7.8±0.3

6.4±0.3 29.3±0.9 41.0±3.0 59.1±1.0

0.6±0.1 2.9±0.1 4.0±0.3 5.9±0.1

1Extraction by DTPA. 2Mean of three determinations + S.D.

PEAR ROOTSTOCKSIN LIME SOIL

15

els. The chlorotic power index (CPI) of the soils was calculated after Pouget and Juste (1972) as: 10 000× (active l i m e ) / ( F e ) 2. Trees were arranged in a completely randomized design with six replicates. At the end of the first growing season ( 1989 ) trees were transplanted to 51 pots; stems were cut 5 cm above the ground to minimize the effects of tree size on second year growth. Visible symptoms of chlorosis, which were rated on a scale from 0 to 5 according to Pouget and Ottenwaelter ( 1978 ), were estimated in September of Year 2 as a single record for clone-soil combination owing to the uniformity of the symptoms. In October 1990, at the end of the second growing season, trees were harvested. One sample of 30 leaves per clone-soil combination (five per tree) was analyzed for mineral elements. Leaves were collected from the mid-shoot zone. Fresh and dry weights of stems and roots and plant height were measured. Dry roots and stems from all trees of each clone-soil combination were ground. A 5 g sample of root and stem per clone-soil combination was analyzed for mineral elements. Nitrogen and P were determined by spectrophotometry and K, Ca, Mg, Fe, Cu, Mn and Zn by atomic absorption spectrophotometry. Mineral content of stems and roots was calculated as the product of mineral concentrations (one value per clone-soil combination) and stem and root dry weights. Analysis of variance (randomized complete design) of the factorial experiment (six clonesX four soils) was performed on growth data using the GLM procedure of Statistical Analysis Systems (SAS Institute, Cary, NC ) and contrast analysis was carried out to identify rootstock response to increasing levels of CaCO3. Simple linear regression was used to relate total lime content of soils and mineral concentrations of tissues within each clone. Regression lines were tested for homogeneity of intercepts and slopes among clones. RESULTS AND DISCUSSION

Soils and soil mixtures differed as to their active lime concentrations, which rose to 9.9% with 33.8% of total lime but only slightly increased in M2 and HC soils (Table 1 ). This is consistent with data reported by Wild (1988), using soils with different levels of carbonate in southern England. The ratio between active and total lime decreased as soil lime increased, suggesting a higher reactivity of carbonate in LC soil (Table 1 ). The CPI of MI and M2 soils, and of HC soil were approximately ten- and 40-fold greater than LC soil's, respectively. Soils showed the same values of bulk pH, a fact suggesting no indirect effect of soil CaCO3 on plant growth via a pH change. Nevertheless, differences between H ÷ concentrations in the bulk soil and in the rhizosphere may also be presumed. Apart from high CaCO3,HC showed Cu and Zn concentrations Soil characteristics. -

16

M. TAGLIAVINIET AL.

nearly ten-fold greater than LC, resulting in increasing contents of these micronutrients as soil lime increased. Growth. - Significant interactions occurred between rootstock and soil CaCO3 for stem and root fresh and dry weights (Table 2, fresh weight data not reported) and plant height at the end of the trial. The patterns of fresh weight and height data of plants recorded at the end of the first growing season ( 1989, data not reported), were similar to final data, although magnitude of difference was less in 1989 than 1990. Patterns of dry matter accumulation in stems of B 21, C 106 and OH × F 51 with increasing soil CaCO3 were similar but differed from those of the other clones (Table 2) as stem dry weight decreased only in HC soil. Adams, D 50 and OH × F 333 were susceptible to soil lime in the two highest CaCO3 concentrations (Table 2 ). Plant heights showed the same pattern. Root dry weight response did not differ from that of stem dry weight, although Adams performed similarly to B 21, C 106 and OH × F 51 (Table 2 ).

TABLE 2

Stem and root dry weights (grams per plant) of selected clones as affected by soil lime Clone

Adams B21 C 106 D 50 OH×F51 OH×F333

Stem dry weight

Root dry weight

Soil lime (%)

Soil lime (%)

1.6

33.8

48.3

72.9

1.6

33.8

48.3

72.9

30,9 15,2 21.7 21,5 8.2 18.6

33.8 19.9 25.8 18.4 14.4 16.8

22.5 18.9 23.1 9.4 9.6 7.0

17.7 11.2 12.7 4.8 5.8 7.4

52.1 26.4 23.2 28.9 10.1 28.1

62.7 34.3 25.9 26.7 12.1 19.2

52.5 34.7 26.5 19.3 8.4 10.8

49.6 16.3 17.8 11.6 6.7 12.4

Significance

Stem dry weight

Root dry weight

NS NS

NS NS

*** NS NS

NS NS **

Soil lime (SL)

Clone (C) Interaction SL × C Contrasts

(B21 vs. C106) × S L (B21 and C106 vs. OHXF51 ) × S L

(B21 and C106 and OH×F51 vs. others) × S L (B21 and C 106 and OH × F51 vs. Adams) X SL ( O H × F 3 3 3 vs. D50) × S L (OH × F 3 3 3 and D50 vs. Adams) × S L *P~< 0.05, **P~< 0.01, ***P~ 0.001.

NS, not significant.

PEAR ROOTSTOCKSIN LIMESOIL

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This certainly does not fit with the reported high susceptibility of quinces to lime-induced iron chlorosis, although data describing quince susceptibility are mainly based on shoot growth and leaf chlorosis (Viti et al., 1989). Furthermore, it is possible that ungrat~ed quinces perform differently from grafted ones as the grafting union plays an important role in regulating the rate of assimilate transport from shoots, which is necessary for root development. Chlorosis. - No symptoms of leaf chlorosis were observed in the clones grown in LC (Table 3). Leaves o r b 21 remained deep green up to 43.8%, CaCO3, although in this soil those of C 106 and OH × F 51 showed onset of chlorosis, whereas the leaves of D 50 and OH × F 333, starting from 48.3% and those of Adams, only at 72.9%, turned deep yellow. The symptoms appeared first and were more severe in young leaves. Several authors have shown high correlations between leaf chlorotic symptoms and chlorophyll contents (Viti and Cinelli, 1989), whereas data of AbaTABLE 3 Effects of soft type and clone on leaf chlorosis symptoms (0=intense green colour; 1 =light green colour; 2 = pale yellow colour; 3 = intense yellow colour; 4 = intense yellow colour with necrosis) Soil

Adams

B 21

C 106

D 50

O H × F 51

O H × F 333

LC Ml M2 HC

0 l 1 3

0 0 0 2

0 0 1 2

0 l 3 3

0 0 2 2

0 1 3 4

Root Ca concentration (mg

g-1 d.w.)

50 OHF 333

40

Other

Intercept

Slope

R2

4.6 b

0.3 a

0.98

16.2 a

0.3 a

0.94

i

i

i

21

31

41

51

O

~

3020 10-

1

11

61

71

Soil C a C O 3 (%)

Fig. 1. Regressions o f root Ca concentration vs. total soil lime. Two separate lines were fitted, one for O H × F 333 (dashed line) and one for the other clones (solid line); letters following parameter estimates show the result o f the test for homogeneity of intercepts and slopes.

18

M. TAGLIAVINIETAL. Root Fe concentration ( r a g g-1 d . w . ) b

~- - ~~~_

Intercept

Slope

R 2

Adams

6.8 a

- 0.04 a

0.83

Other

5.6 b

- 0.04 a

0.84

OHF 3 3 3

3.6 c

- 0.04 a

0.90

i

i

41

51

61

•

11

21

31

71

Soil C a C O 3 (%)

Fig. 2. Regressions of root Fe concentration vs. total soil lime. Three separate lines were fitted, one for O H × F 333 (dotted line), one for Adams (dashed line) and one for the other clones (solid line); letters following parameter estimates show the result of the test for homogeneity of intercepts and slopes. Root Mn concentration (/Jg g-1 d . w . )

200

!a Intercept OHF 333

150

Other

Slope

R 2

84

b

-0.82 a

095

131

a

-0.82 a

0.86

100

50

11

i

i

21

31

i

41

51

61

71

Soil CaCO 3 (%)

Fig. 3. Regressions of root Mn concentration vs. total soil lime. Two separate lines were fitted, one for O H × F 333 (dashed line) and one for the other clones (solid line); letters following parameter estimates show the result of the test for homogeneity of intercepts and slopes.

dia et al. (1989) showed that specific leaf weight of chlorotic pears trees averaged 33% less than corresponding green leaves. This evidence may in part explain the agreement of growth response and chlorosis development, a decrease in the former being a consequence of the latter.

PEAR ROOTSTOCKS IN LIME SOIL

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Leaf mineral analysis revealed no change in element composition with increasing soil lime (data not shown). Except for Ca, similar results were found for stem mineral analysis. Total soil lime was positively related with root Ca concentration in all clones (Fig. 1 ) and with stem Ca concentration in B 21 and OH X F 51 (data not shown), and negatively related to root iron concentration (Fig. 2). The rates of increase of calcium and decrease of iron did not differ among clones. The higher content of calcium recorded by plants grown under increasing lime concentration may be related to larger amounts of available calcium in soil solution, as indicated by the active lime values in Table 1. Furthermore, it should be considered that adaptive strategies of iron efficient plants include an enhancement in cation uptake so as to decrease rhizosphere pH (Romera et al., 1991 a, b). This may also occur in pears and quinces grown under high soil CaCO3. Table 4 shows the Fe content of stems and roots at the end of the trial. These data indicate that only a small percentage of root iron was translocated to shoots, suggesting that growth depression and plant susceptibility to soil carbonate are unlikely to be associated with a reduced translocation of Fe from roots to aerial organs. In fact, despite a reduction of stem and root Fe content, all clones but Adams and B 21 increased the stem-to-root ratio of iron content so long as soil lime increased, a fact that may, at least in part, explain the lack of difference in leaf total iron content between plants grown in high lime conditions and non-calcareous soils. Our findings fit with previous results on blueberry plants reported by Korcak (1989), who found that Mineral

content.

-

Root Cu concentration (pg g-1 d.w.) 160

a

R 2= 0.96

140 120 1O0 80 60 40 20 0 10

i

i

i

F

~

i

i

i

i

L

15

20

25

30

35

40

45

50

55

60

Soil CU concentration (pg g .1)

Fig. 4. Regression o f root Cu c o n c e n t r a t i o n as a function o f soil Cu concentration. One single line was fitted to data for all rootstocks. Circles represent the m e a n of six data.

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M. TAGLIAVINIET AL.

TABLE4 Ironcontent(milligramsperplant)instem (S)androots(R)ofselectedclonesasaffectedbysoil Soil

LC M1 M2 HC

Adams

B 21

C 106

D 50

O H × F 51

O H × F 333

S

R

S

R

S

R

S

R

S

R

S

R

11 9 6 4

347 385 227 150

11 4 4 3

142 94 120 44

3 3 3 2

127 99 125 26

6 3 2 2

169 92 49 20

2 2 2 1

54 46 38 12

2 2 1 1

88 36 12 14

Interaction SEM=0.5 and 1 4 f o r s t e m a n d root Fe, respectively.

only 2.3% of total iron was present in shoots. It should be considered, however, that root iron content does not necessarily correspond to iron uptake, as shown by Kolesch et al. (1987a, b), who found that under high carbonate concentrations iron can be adsorbed through the root surface, although the mechanism of iron uptake in the roots may be disrupted. Our data also suggest a depression of root Mn concentration in all clones as soil lime increased (Fig. 3), which accords with data reported in grapes by Mengel et al. (1984). Iron and Mn may thus be similarly affected by soil carbonate. Root Cu concentration increased linearly with soil Cu content (Fig. 4). The regression lines for oach clone coincided, as both slopes and intercepts were homogeneous. Soil Zn content was not linearly related to root Zn concentration (data not shown). Mengel et al. (1984), who studied grape nutrition in calcareous soil (24.4% C a C O 3 ), found Cu and Zn concentrations respectively 35- and five-fold higher than in non-calcareous soil; while they did not record any effect of soil Cu and Zn on uptake of these elements, it should be noted that they only performed leaf mineral analysis. Roots are thought to be the most sensitive organs to Cu toxicity, although they respond to high soil Cu by increasing their Cu concentrations, whereas Cu translocation to shoots may remain unaffected (Rahimi and Bussler, 1974), as also indicated by the lack of soil effect on stem Cu concentrations (data not shown). Although we have not found in the literature any information about the optimum range of Cu in roots of pear and quince, it is possible that plants grown in lime soils face negative consequences of high soil Cu, including leaf chlorosis. Some authors (Reuther and Smith, 1953; Smith and Specht, 1953) have considered Cu toxicity as a cause of leaf iron chlorosis, and Brown and Holmes (1956 ) suggested that chlorosis is unlikely to occur so long as Cu and Mn remain low.

PEARROOTSTOCKSIN LIMESOIL

21

CONCLUSIONS

The pear and quince rootstocks tested in this trial showed varying susceptibility to soil carbonate: three clones of pear (B 21, C 106 and O H × F 51 ) were more tolerant than quince Adams and pears D 50 and O H × F 333. Although there is a need to know whether grafted pear and quince respond in a similar way as ungrafted ones to lime-induced iron chlorosis, the choice of a tolerant rootstock must be taken into account when growing pear in lime soils. In grafted trees it is possible, however, that mechanisms other than iron uptake are involved in leaf chlorosis. Our data indicate that susceptibility to lime soil may be related to CPI and total carbonate in more tolerant (B 21, C 106 and OH X F 51 ) and susceptible ( O H × F 333 and D 50) clones, respectively, but not to active lime. Growth depression and plant susceptibility to soil carbonate do not appear related to a reduced translocation of iron from roots to shoot. Our findings indicate that high lime soils may lead to impaired Fe and Mn uptake; the higher content of Cu in the calcareous soil may also have contributed to inducing leaf chlorosis. ACKNOWLEDGMENTS

Research partially supported by Centro Attivita Vivaistiche (C.A.V., Italy) and H.U.R.S.T. (40% program). REFERENCES Abadia, A., Sanz M., De las Rivas J. and Abadia J., 1989. Pear yeUowness: an atypical form of iron chlorosis? Acta Horticulturae, 256:177-181. Baldini, E., 1953. Ricerche sulla disaffinita d'innesto del pero Imperatore Alessandro (Kaiser) su cotogno. Rivista della Ortoflorofrutticoltura, Italiana, 78 (9-10): 1-12. Bassi, D., Marangoni B. and Barnab~ D., 1989. Selection of pear seedlings (P. communis L. ) as potential clonal rootstocks: preliminary data. Acta Horticulturae, 256: 43-52. Brooks, A., 1984. History of the Old Home × Farmingdale pear rootstocks. Fruit Var. J., 3:126128. Brown, J.C. and Holmes R.S., 1956. Iron supply and interacting factors related to lime-induced chlorosis. Soil Sci., 82:507-519. Chancy, R.L. and Bell P.F., 1987. Complexity of iron nutrition: lessons for plant-soil interaction research. J. Plant Nutr., 10 (9-16 ): 963-994. Chen, Y. and Barak P., 1982. Iron nutrition of plants in calcareous soils. Adv. Agron., 35:217240. Kolesch, H., Hofner H. and Schaller K., 1987a. Effects of bicarbonate and phosphate on iron chlorosis of grape vines with special regard to the susceptibility of two rootstocks. Part I: field experiments. J. Plant Nutr., 10(2): 207-230. Kolesch, H., Hofner H. and Schaller K., 1987b. Effects of bicarbonate and phosphate on iron chlorosis of grape vines with special regard to the susceptibility of two rootstocks. Part II: pot experiments. J. Plant Nutr., 10(2): 231-249.

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Korcak, R.F., 1987. Iron deficiency chlorosis. Hortic. Rev., 9: 133-186. Korcak, R.F., 1989. Influence of micronutrient and phosphorus levels and chelator to iron ratio on growth, chlorosis, and nutrition of bluecrop highbush blueberries. J. Plant Nutr., 12 ( 11 ): 1293-1310. Marschner, H., 1986. Mineral Nutrition of Higher Plants. Academic Press, London, 674 pp. Mengel, K., Breininger M.Th. and Bulb W., 1984. Bicarbonate, the most important factor inducing iron chlorosis in vine grapes on calcareous soil. Plant Soil, 81: 333-344. Michelesi, J.C., 1991. I portinnesti del pero. Rivista di Frutticoltura, 53( 11 ): 29-33. Pouget, R. and Juste C., 1972. Le choix des porte-greffes de la vigne pour les sols calcaires. Connaissance de la Vigne et du Vin, 4: 357-364. Pouget R. and Ottenwaelter M., 1978. Etudie de l'adaptation de nouvelles varietes de portegreffes a des sols tres chlorosants. Connaissance de la Vigne et du Vin, 3:167-175. Rahimi, A. and Bussler W., 1974. Kuperfermangel bei hoheren Pflanzen und sein histochemischer narchweis. Landwirtsch. Forsch., 30(2): 101-111. Reuther, W. and Smith P.F., 1953. Effects of high copper content of sandy soil on growth of citrus seedlings. Soil Sci., 75: 219-224. Romera, F.J., Alcantara E. and De La Guardia M.D., 1991 a. Characterization of the tolerance to iron chlorosis in different rootstocks grown in nutrient solution. 1. Effects of bicarbonate and phosphate. Plant Soil, 130:115-119. Romera, F.J., Alcantara E. and De La Guardia M.D., 1991 b. Characterization of the tolerance to iron chlorosis in different rootstocks grown in nutrient solution. 2. Iron stress response mechanisms. Plant Soil, 130:121-125. Smith, P.F. and Specht A.W., 1953. Heavy metal nutrition and iron chlorosis of citrus seedlings. Plant Physiol., 28:371-382 Statistical Analysis Systems, 1988. SAS/STATT M User's Guide, Release 6. 03 Edn., SAS, Cary, NC, 1028 pp. Viti, R. and Cinelli F., 1989. Evaluation of some clonal quince rootstocks in calcareous soil. Acta Hortic., 256: 53-61. Viti, R., Loreti F. and F. Cinelli, 1989. La valutazione dei portinnesti per la resistenza alia clorosi calcarea. Rivista di Frutticoltura, 51 (8/9 ): 27-32. Wild, A. (Editor), 1988. Russell's Soil Conditions and Plant Growth. Longman Scientific & Technical, Harlow, UK, 991 pp.