Rootstock influence on leaf and fruit mineral status of ‘Bartlett’ and ‘d'Anjou’ pear

Scientia Horticulturae, 23 (1984) 41--49

41

Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

ROOTSTOCK INFLUENCE ON LEAF AND FRUIT MINERAL OF 'BARTLETT' AND 'D'ANJOU' PEAR

STATUS

ESMAEIL F A L L A H I and FENTON E. LARSEN

Department of Horticulture and Landscape Architecture, Washington State University, College of Agriculture, Pullman, WA 99164-6414 (U.S.A.) Scientific Paper No. 6542, Project 1639 (Accepted for publication 10 October 1983)

ABSTRACT

Fallahi, E. and Larsen, F.E., 1984. Rootstock influence on leaf and fruit mineral status of 'Barl:lett' and ' d ' A n j o u ' pear. Scientia Hortic., 23: 41--49. In a test with 'Bartlett' and ' d ' A n j o u ' pear on 8 Pyrus (P.) rootstocks, leaves of 'Bartlett' were high in S and Fe on 'Bartlett' seedlings (BS), in Zn on P. ussuriensis Maxim. seedlings (USS), and in B on seedlings of P. calleryana Decne (Cal). Leaves of ' d ' A n j o u ' were high in P, Zn and B on BS, in N on USS, and in S on Cal. Both 'Bartlett' and ' d ' A n j o u ' were high in K and Ca on P. betulaefolia Bunge seedlings (Bet). Fruit of both 'Bartlett' and ' d ' A n j o u ' were high in N, K and Mg on Bet and Cal and high in Ca on Cal and USS. With both 'Bartlett' and ' d ' A n j o u ' , moderately high correlations were found between leaf and fruit concentrations of K and Mg; positive correlations were high for Ca and S with 'Bartlett' and for Zn and B with 'd'Anjou'. There was a very high negative correla;ion between leaf and fruit Ca with 'd'Anjou'. Keywords: mineral status; Pyrus betulaefolia; Pyrus calleryana; Pyrus communis; Pyrus

usseriensis.

ABBR:EVIATIONS B e t , betulaefolia; BS, B a r t l e t t s e e d l i n g ; Cal, Calleryana; I F , i m p o r t e d F r e n c h ; O H , O l d H o m e ; O H × F, O l d H o m e × F a r m i n g d a l e ; P, P y r u s ; U S S , ussuriensis; W N , W i n t e r N e l i s . INTRODUCTION Pear rootstocks are known to affect the concentration of mineral elements in s c i o n l e a v e s ( W e s t w o o d a n d L o m b a r d , 1 9 6 6 ; T e r b l a n c h e t al., 1 9 7 0 ; Woodbridge, 1973; Chaplin and Westwood, 1980a,b). Most attention has b e e n p a i d t o t h e i n f l u e n c e o f r o o t s t o c k s o n l e a v e s o f ' B a r t l e t t ' , w i t h less attention to 'd'Anjou' and other cultivars (Lombard and Westwood, 1975; W e s t w o o d a n d L o m b a r d , 1 9 7 7 ) . W o r k in O r e g o n ( L o m b a r d a n d W e s t w o o d ,

0304-4238/84/$03.00

© 1984 Elsevier Science Publishers B.V.

42 1975; Westwood and Lombard, 1977) noted the highest leaf concentration of P with several pear cultivars on Bet, of Ca and Mg on OH and IF, and of Ca and B on Cal. Woodbridge {1973) found lower 'Bartlett' leaf concentrations of Ca and Mg on OH and IF than from most other rootstocks tested. Research to date on pear rootstocks has not related mineral concentrations of leaves and fruit, although physiological disorders of pear fruit have been related to nutrient problems (Wauchope, 1966; Mason and Welsh, 1970; Woodbridge, 1971; Raese et al., 1979). Therefore, this study was done to relate the mineral concentrations of leaves and fruits as influenced by rootstocks. MATERIALS AND METHODS Pear leaves and fruits were obtained from trees grown in central Washington at the Washington State University Royal Slope Research Unit northwest of Othello, Washington, U.S.A. The trees were planted 3 X 6 m apart, in 1965, on a fine, sandy loam soil. The experimental design was a randomized block with 3 replications of 8 treatments (rootstocks) and 4 trees per plot, to give 12 trees per scion/rootstock combination. An 'Illahee Creeping Red' fescue cover was used between rows. Trees were irrigated with overhead sprinklers. 'Bartlett' and 'd'Anjou' scions were grafted on 8 rootstocks: USS, BS and IF seedlings from Pacific Coast Nursery, Oregon; WN and Bet seedlings from Fowler Nursery, California; Cal seedlings from Whiterock Nursery, Texas; OH (Talent strain) and OH X F (unselected, un-numbered stock) were vegetatively propagated from Carlton Nursery, Oregon. During the year of the study {1977), dormant zinc sulfate (36%) and Solubor cover sprays supplied Zn and B, while N as NH4NO3 was broadcast under the trees at the rate of 250 kg ha -1. Similar applications had been made in previous years. Fruits were hand-thinned (to levels that would avoid limb breakage) following the June drop in 1977. Fifty mid-shoot leaves were taken from each quadrant of each tree in a plot on 19 July 1977. Ten fruits were randomly picked from each tree ('Bartlett', 12 August; 'd'Anjou', 26 August) in the same manner as the leaf sampling. Leaf and fruit samples were washed with distilled water. A 7-mm cork borer was used to take the tissue samples from 6 different spots on each fruit. To prevent sampling where there might be a mineral accumulation in one spot or area of the fruit, the cork borer was pushed completely into the core area. Seeds and endocarp tissue were discarded. Leaf and fruit samples from each tree were dried in a forced-air oven at 70°C and ground in a Wiley mill to pass a 40-mesh screen. Both leaf and fruit samples of each tree were ashed and separately analyzed, and the following methods were used for specific mineral element analysis: N, kjeldahl; P, phosphomolybdate; Fe, thiocyanate; B, quinalizarin; S turbidimetric. N, P, Fe, B and S were measured spectrocolorimetrically (Bausch and Lomb Spectronic 20), and Mg, Mn, Zn and Cu were measured

43 by the atomic absorption m e t h o d (aa/ae Spectrophotometer). Ca and K were determined by flame emission (Beckman Model B). RESULTS AND DISCUSSION minerals. - - 'Bartlett' leaves on BS had significantly higher concentration~,~ of S than those on Bet, OH and OH X F, and also had higher Fe than those on Bet, Cal, IF and OH. 'Bartlett' leaves on Bet had significantly higher K and Ca than those on BS, IF, OH and OH X F, while those on Cal had more Mg than those on BS, IF, OH, OH X F and WN (Table I). 'D'Anjou' leaves on Bet had relatively high levels of K and Ca, while those on Cal had high concentrations of Mg and S. 'D'Anjou' leaves on USS had significantly higher N than those on BS, Bet, Cal, IF and OH, and higher Mn than those on Bet, Cal and WN. Both 'Bartlett' and 'd'Anjou' leaves had low levels of N, P, K, S, Cu and B on OH, of Ca and Mg on IF and of Mn on Bet, while leaves of both cultivars had high levels of P and Mn on USS, of K and Ca on Bet, of Cu on IF and USS, and of B on Cal compared to most other rootstocks. Therefore, the use,' of Cal for 'Bartlett', USS for 'd'Anjou' and Bet for both 'd'Anjou' and 'Bartlett' could reduce the amount of K, Mg and B fertilizer applications for ea(',h of these scion/rootstock combinations, respectively. However, the data might also suggest that these combinations may actually require higher levels of these respective elements in order to produce good yields. In t:~is research, Bet, Cal and OH did not, as a group of vigorous rootstocks (Westwood et al., 1976), show a similar influence on the mineral uptake of scion leaves. Lombard and Westwood (1975, 1976) found that various,; cultivars of pear had high levels of K on Bet and Cal, of Mn on OH, of Zn on WN, and of B on Cal, which agrees with our research. These results are also in general agreement with Woodbridge (1973) for 'Bartlett' pear. Ove:call, 'Bartlett' leaves had significantly higher levels of N, P, S, Cu and B than 'd'Anjou' leves, while K, Ca and Mg concentrations of 'd'Anjou' leaves were higher than for 'Bartlett'. However, other differences were small. Leaf

m i n e r a l s . - - 'Bartlett' fruits on Cal were high in N, P, K, Mg, Mn and Fe, while those on OH and OH X F had lower levels of these elements (Table II). High levels of N in 'Bartlett' fruits on both Bet and Cal and a low concentration of this element in the fruits on OH could be responsible for the dark green fruits on Bet arid Cal and lighter colored fruits on OH, as previously reported (Fallahi and Larsen, 1981). 'D'Anjou' fruits on Bet had high concentrations of K, Mg, Zn and Fe, and of Ca on Cal; while those on BS had low N, P, K, Mg and Mn (Table II). Relati'vely high ratios of K/Ca and Mg/Ca in 'd'Anjou' fruit on Bet may have contributed to the incidence of cork spot on these fruits, as reported earlier (Fallahi and Larsen, 1981). High K/Ca and Mg/Ca ratios have been shown to be associated with bitter pit in apples (Sharpies, 1980), suggesting that, not

Fruit

2.55 a 0.229 b 1.48 c 1.80 bc 0.36bc 0,171 a 43.0 ab 17.3 be ll.7a 209.4 a 35.8 abc

Bartlett (BS)

1.84 cd 0.225 a 1.80 be 2.26 be 0.36 ab 0,129 b 41.3 ab 20.8a 8,9 b 153.5a 36.4 a

leaves

N (%) P (%) K (%) Ca (%) Mg (%) S (%) M n ( r a g 1-1) Z n ( m g l ]) C u ( m g 1- l ) F e ( m g l 1) B (mgl -l)

'D'Anjou'

N (%) P (%) K (%) Ca ( % ) Mg (%) S (%) M n ( r a g 1 1) Zn (rag yl) Cu(mg1-1) F e ( r a g 1-1 ) B ( r a g 1 1)

'Baxtlett' leaves

Mineral

1.81 cd 0.190 cde 2.01 a 2.89 a 0.36 ab 0,130 b 36,5 b 17.3bc 9.6 b 166.2a 28.4 cd

1.92 bc 0.180 e 1.85 abe 2.26 bc 0.38 a 0.147 a 38.0 b 14.4d 9.0 b 171.2a 32.5 abc

2.32 a 0.234 ab 1.69 ab 1.68 bc 0.41 a 0.160 ab 43.7 ab 17.8 bc 12.1a 177.1 bc 43.3 a

(Cal)

(Bet)

2.38 a 0.217 b 1.81 a 2.23 a 0.38 ab 0.142 bcd 40.9 b 16.7 c 10,7a 167.1 c 34.8 bc

Pyrus ealleryana

Pyrus betuk~efolia

1.93 bc 0.200 bede 1.69 e 2.17 e 0.34 b 0.141 ab 43.2 ab 15.7 cd 12.2 a 185.1 a 30.6 bcd

2.47 a 0.233 b 1.58 bc 1.60 c 0.32 cd 0.154 abc 48.2 a 18.9 abc 12.4a 172.9 bc 30.3 c

Imported French (IF)

1.77 d 0.187 de 1.78 bc 2.39 be 0.40 a 0.131 b 48.4 a 20.2 ab 7.4 c 170.6 a 26.5 d

2.45 a 0.223 b 1.50 bc 1.87 b 0.31 d 0.134 d 43.5 ab 18.1 bc 11.3a 179.6 bc 34.1 bc

Old Home (OH)

2.02 ab 0.208 abcd 1.85 abe 2.63 ab 0.37 ab 0.129 b 42.1 ab 19.4 ab 8,5 bc 218.8 a 31,6 bc

2.44 a 0.225 b 1.55 bc 1.82 bc 0.33 cd 0.136 ed 39.2 b 16.7 c 10.6a 196.5 ab 30.8 c

Old Home X Farmingdale (OH X F)

2.14 a 0.222 ab 1.87 abc 2.43 be 0.36 ab 0.146 ab 49.5 a 19.2 ab 12.5 a 161.6a 30.4 bcd

2.33 a 0.258 a 1.59 bc 2.24 a 0.41 a 0.166 a 49.1 a 21.3 a 12.1a 180.3 abc 40.4 ab

(USS)

Pyrus ussuriensis

2.02 ab 0.212 abc 1.89 ab 2.51 bc 0.40 a 0.135 ab 39,8 b 19.7 ab 9.8 b 155.8 a 34.1 ab

2.34 a 0.236 ab 1.68 ab 1.65 bc 0.34 cd 0,167 a 42.3 b 19.5 ab 10.9a 196.6 ab 35.9 abc

Winter Nelis (WN)

1.93 0.203 1.84"* 2.44** 0.37** 0.136 42.4 18.3 9.7 172.9 31.3

2.41"* 2.232** 1.61 1.86 0.36 0.154"* 43.7 18.3 11.5, 184.9 35.7*

Mean

Mineral levels of leaves from 'Bartlett' and 'd'Anjou' trees on different rootstocks. Values per cultivar within rows followed by the same letter are not s i g n i f i c a n t l y d i f f e r e n t w i t h D u n c a n ' s m u l t i p l e r a n g e t e s t , 5 % , ' B a r t l e t t ' a n d ' d ' A n j o u ' m e a n s a r e s i g n i f i c a n t l y d i f f e r e n t as i n d i c a t e d b y u n p a i x e d t - t e s t , 1% (**) or 5% C*)

TABLE I

H

0.34 b 0.125 b 1.13 c 0.105 ab 0.356 b 0.077 a 3.9 b 6.9 b 8.4 bc 66.6bc 27.7 a

10.8 c 3.4 b

K/Ca ratio Mg/Ca ratio

fruits

0.54 bc 0.115 b 1.21 bc 0.078 abc 0.430 c 0.218 a 3.7 b c 12.9a 17.0a 31.5 b 19.4a

Bartlett (BS)

N (%) P (%) K (%) Ca ( % ) Mg (%) S (%) M n ( m g 1-1) Z n ( r a g 1-1) C u ( m g 1-1 ) Fe(mg1-1) B ( r a g 1-1)

'D'Anjou'

N (%) P (%) K (%) Ca ( % ) Mg (%) S (%) M n ( r a g 1-1 ) Zn(ragl -I) Cu(mg1-1) F e ( m g 1-1) B ( r a g l 1)

'Bartlett' fruits

Mineral

14.3 b 4.4 ab

0.48 ab 0.158 a 1.46 a 0.102 ab 0.450 a 0,061 a 5.1 a 10.9 a 9.3 bc 98.3a 19.7 c 11.6 c 3.8 b

0.51 a 0.133 ab 1.34 ab 0.116 a 0.443 a 0.080 a 4.7 ab 7.0 b 9.8 bc 65.3bc 22.1 abc

0.74 a 0.140 a 1.42 a 0.085 ab 0.540a 0.139 abc 4.6 a 12.5a 22.5a 43.5 a 17.9a

(Ca])

(Bet)

0.63 ab 0.114 b 1.33 ab 0.078 abc 0.530 ab 0.118 bc 4.7 a ll.0a 12.5a 29.5 b 18.5a

Pyrus calleryana

Pyrus betulacfolia

13.3 b 4.2 ab

0.50 a 0.143 ab 1.26 bc 0.095 ab 0.400 ab 0.066 a 4.5 ab 7.2 b 11.7 a 66.6bc 24.9 ab

0.48 c 0.108 b 1.10 c 0.067 c 0.385 c 0.179 ab 2.4 c 13.5a 19.5a 33.0 b 17.9a

Imported French (IF)

11.1 c 3.7 b

0.42 ab 0.130 ab 1.13 c 0.102 ab 0.376 b 0.042 a 4.9 ab 10.5 a 8.1 c 72,6bc 18.9 c

0.42 c 0.101 b 1.06 a 0.078 abc 0.385 e 0.059 c 3.3 bc 14.5a 20.5a 29.5 b 17.4a

Old Home (OH)

17.1 a 5.3 a

0.48 ab 0.131 ab 1.28 bc 0.075 b 0.400 ab 0.042 a 4.4 ab 7.2 b 8.0 c 52.0c 23.5 abc

0.46 e 0.100 b 1.05 c 0.078 abc 0.400 e 0.065 c 3.3 c 18.5a 28.0a 26.0 b 16.6a

Old Home X Farmingdale (OH X F)

10.6 c 3.7 b

0.44 ab 0.130 ab 1.15 c 0.109 a 0.400 ab 0.072 a 4.1 b 6.0 b 9.9 b 86.0ab 20.6 bc

0.53 be 0.112 b 1.17 bc 0.092 a 0.480 ahc 0.118 bc 4.3 ab 16.0a 25.0a 30.0 b 15.2a

(USS)

Pyrus ussuriensis

13.5 b 4,3 ab

0.48 ab 0.138 ab 1.28 bc 0.095 ab 0.413 ab 0.072 a 4.5 ab 7.0 b 9.8 bc 53.0c 22.7 abc

0.48 c 0.110 b 1.10 c 0.071 bc 0.435 bc 0.103 bc 3.6 bc 15.3a 24.0a 28.0 b 16.0a

Winter Nelis (WN)

0.46 0.136"* 1.25 0.100"* 0.405 0.064 4.5 7.8 9.4 70.1"* 22.5**

0,54 0.113 1.18 0.078 0.488 0.125"* 3.7* 14.3"* 21.1 ~* 31.4 17.4

Mean

Mineral levels of fruits from 'Bartlett' and 'd'Anjou' trees on different rootstocks. Values per cultivar within rows followed by the same letter are not s i g n i f i c a n t l y d i f f e r e n t w i t h D u n c a n ' s m u l t i p l e r a n g e t e s t , 5%. ' B a r t l e t t ' a n d ' d ' A n j o u ' m e a n s a r e s i g n i f i c a n t l y d i f f e r e n t as i n d i c a t e d b y u n p a i r e d t - t e s t , 1 % ('~'~) o r 5 % ( ~ )

TABLE

46 only the Ca levels of fruits, but also K/Ca and Mg/Ca ratios might be calculated to help predict 'd'Anjou' fruit storage disorders. However, the K/CA and Mg/Ca ratios of 'd'Anjou' fruit on OH X F were highest (numerically if not statistically) because of low Ca levels, and no cork spot occurred on these fruits (Fallahi and Larsen, 1981). Further study is required to help explain these findings. In general, 'Bartlett' fruits had significantly higher mean levels of S, Mn, Zn and Cu, while 'd'Anjou' fruits had higher P, Ca, Fe and B. Comparison o f fruit and leaf minerals. -- With some rootstocks, concentrations of some minerals in the scion fruits fluctuated in the same pattern as in scion leaves. For example, both leaves and fruits of 'd'Anjou' had high levels of B on BS, of K on Bet, of S on Cal, of Cu on IF and USS, and of Mn on OH. Also, both 'Bartlett' fruits and leaves had high levels of S on BS, of K on Bet, and of Ca on USS. Therefore, for these elements, with these combinations of scions and rootstocks, leaf analysis should be sufficient for determining fruit nutrient needs. For other situations, leaf analysis alone may not be sufficient. For determination of 'd'Anjou' fruit Ca level, fruit analysis seems to be particularly essential. As an example, 'd'Anjou' leaves on Bet had the highest concentration of Ca, while 'd'Anjou' fruits on the same rootstock had a moderate-to-low level of Ca. Correlations were strong between some fruit and leaf mineral levels, but negligible in others (Table III). In some cases, the correlation between a mineral element in the leaf and the same or another element in the fruit was negative in 'Bartlett' but positive in 'd'Anjou'. For example, 'Bartlett' leaf and fruit N were negatively correlated, while this correlation in 'd'Anjou' was positive. This might suggest that the mechanism of xylem and phloem loading, and the transport from leaf to fruit in 'Bartlett' are different than in 'd'Anjou'. These correlations might also suggest that 'Bartlett' fruit would not accumulate as much N and B as 'd'Anjou' with increasing fertilizer application, while both 'Bartlett' and 'd'Anjou' would tend to accumulate K in the fruit. While Ca accumulated in 'Bartlett' fruit (r = 0.63) but not 'd'Anjou' (--0.94), both accumulated P, K, Mg, Mn, S and Zn. We might suspect that heavy N fertilizer application would lead to mineral imbalances in the fruit, particularly N and Ca, resulting in storage disorders. Based on these correlations, it seems t h a t leaf analysis alone may generally be a valid indicator of fruit nutrient needs for the elements K, Ca, Mg and S in 'Bartlett' and K, Mg, Zn, Fe and B in 'd'Anjou' fruit. However, it would be essential to analyze fruit tissue to detect fruit Ca concentrations in 'd'Anjou' fruits. There were several strong correlations between various pairs of elements in both 'd'Anjou' and 'Bartlett' leaves and fruit (i.e. leaf Mg and fruit Mn or leaf Mg and fruit N). Further studies are required on the significance of such relationships.

47 TABLE III Correlation coefficients (r) between mineral concentrations of leaf and fruit of 'Bartlett' and 'd'AJljou' pears. Values marked * or ** are significant at 5 or 1%, respectively Pair of elements r values

Pair of elements r values

Leaf

Fruit

'Bartlett'

'd'Anjou'

Leaf

Fruit

'Bartlett'

'd'Anjou'

N N N N N N N

Ca K N P Mn Zn S

--0.44* --0.39 --0.46* --0.44* --0.62** --0.02 0.40

--0.002 --0.14 0.30 --0.60** --0.56** -0.51"* 0.97**

Mn Mn Mn Mn Mn Mn Mn

P Ca Zn Cu Fe B Mn

0.10 0.23 --0.07 0.05 0.26 --0.28 0.10

0.57** -0.92** 0.82** --0.58** 0.50* --0.79** 0.23

P P P

N P Ca

0.02 0.17 0.54**

--0.53** 0.17 --0.51"*

Zn Zn Zn

Zn Fe B

0.26 --0.02 --0.71"*

0.58** 0.63** -0.58**

K K K K K K

N P K Ca Fe Mg

0.63** 0.45* 0.63** 0.03 0.20 0.76**

--0.43* 0.67** 0.64** 0.02 0.71"* 0.27

Cu Cu Cu Cu Fe Fe

P Zn S Cu Fe N

0.42* --0.24 0.61"* 0.004 --0.30 --0.32

--0.67** --0.54** 0.89** --0.04 0.48* --0.62**

Ca Ca Ca Ca Ca Ca

P K Ca Zn Cu B

--0.11 0.20 0.63** --0.08 --0.25 --0.18

0.52** 0.17 --0.94** 0.80** 0.62** -0.76**

B B B B B B

P Mn N Zn B S

0.80** 0.72** 0.71"* --0.28 --0.17 0.11

--0.59** --0.89** --0.38 --0.72** 0.67** 0.54**

Mg Mg Mg Mg Mg Mg

N K Ca Mg Mn B

0.79** 0.77** 0.79** 0.88** 0.89** --0.11

0.97** 0.40 --0.11 0.49* 0.66** --0.61"*

S S S

N Mn S

0.29 0.24 0.69**

--0.55** --0.64** 0.31

I n f l u e n c e o f c r o p load. - - C r o p l o a d m a y have h a d s o m e e f f e c t o n l e a f a n d f r u i t n u t r i e n t levels, b u t t h e t r e n d s in t h i s d i r e c t i o n w e r e o n l y t o a v e r y l i m i t e d d e g r e e w h a t m i g h t have b e e n e x p e c t e d if p e a r s r e s p o n d as r e p o r t e d f o r a p p l e s ( L o r d a n d B r a m l a g e , 1 9 8 3 ) . A c c o r d i n g t o this r e p o r t , leaves o f l i g h t - c r o p p i n g t r e e s s h o u l d have l o w e r N, Ca a n d Mg a n d h i g h e r K, w i t h no d i f f e r e n c e in P. F r u i t s h o u l d be h i g h e r in K a n d l o w e r in Ca, w i t h n o diff e r e n c e in N, P a n d Mg. B o t h ' B a r t l e t t ' a n d ' d ' A n j o u ' / U S S h a d c o m p a r a t i v e l y l o w y i e l d s ( T a b l e IV), b u t n u t r i e n t levels s h o w e d v e r y l i t t l e t e n d e n c y t o r e s p o n d as s u g g e s t e d a b o v e w h e n c o m p a r e d w i t h o t h e r r o o t s t o c k s . W i t h ' B a r t l e t t ' f r u i t , K was high w i t h b o t h B e t a n d Cal r o o t s t o c k s , w h i l e t h e s e rootstocks produced the highest and lowest yields, respectively.

48 T A B L E IV M e a n yields ( M T h a "~, 1 9 7 7 ) o f ' B a r t l e t t ' a n d ' d ' A n j o u ' pears o n several r o o t s t o c k s . M e a n s are f r o m 3 p l o t s o f 4 trees each; m e a n s e p a r a t i o n b y D u n c a n ' s m u l t i p l e range test, 5% Rootstock

'Bartlett'

'd'Anjou'

B a r t l e t t (BS)

33.7 37.4 20.0 35.5 33.0 37.1 22.2 29.7

34.6 31.0 31.3 26.6 14.8 37.8 21.7 35.6

P. betulaefolia ( B e t ) P. calleryana (Cal) Imported French (IF) Old H o m e (OH) Old H o m e X F a r m i n g d a l e ( O H X F ) P. ussuriensis (USS) Winter Nelis (WN)

a a b a a a b ab

ab abc abc bc d a cd ab

CONCLUSIONS

In choosing a rootstock, its adaptation to local conditions and its known influences on the scion fruit quality and yield must be carefully considered. As shown in this research, rootstocks can influence fruit as well as leaf nutrient status. It might be possible to take advantage of these effects in situations where specific elements are a problem (high or low according to the situation). For example, Cal might be used for both 'Bartlett' and 'd'Anjou' where B deficiency is a problem, as B levels in the scion tissues on this rootstock were relatively high. On the other hand, in an area of Zn deficiency, trees on Cal may require more attention than some rootstocks in order to avoid Zn shortage. Bet might be used for 'Bartlett' and 'd'Anjou' for better K uptake, but the quality of 'd'Anjou' fruit on this rootstock is poor (Fallahi and Larsen, 1981). It might be possible to solve the problem of poor quality in 'd'Anjou'/Bet by using an interstock between the 'd'Anjou'/Bet combination, which would lower the K/Ca ratio in the 'd'Anjou' fruits, leading to less incidence of cork spot. In alkaline and poorly aerated soils, IF and OH might be used in order to absorb more Mn. While the data may be interpreted as above, suggesting that certain rootstocks should or should not be used in certain situations, another possible interpretation is that there should be a different set of recommended nutritional levels for each scion/rootstock combination, and that nutrients should be applied accordingly. The results of leaf analyses may not be good indicators of nutrient levels in other scion parts. While there may be good correlations in some cases, there may be little or none in others.

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