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The relative effects of rootstocks and calcium sprays on the appearance of internal breakdown and superficial scald of ‘Red Delicious’ apples during storage
Scientia Horticulturae, 9 (1978) 245--249 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
245
THE RELATIVE EFFECTS OF ROOTSTOCKS AND CALCIUM SPRAYS ON THE APPEARANCE OF INTERNAL BREAKDOWN AND SUPERFICIAL SCALD OF ' R E D D E L I C I O U S ' APPLES D U R I N G S T O R A G E
J.B. O'LOUGHLIN and P. JOTIC Department of Agriculture, New Town Research Laboratories, St. John's Avenue, New Town, Tasmania, 7 00~ (Australia)
(Received 3 February 1978)
ABSTRACT O'I~ughlin, J.B. and Jotic, P., 1978. The relative effects of rootstocks and calcium sprays on the appearance of internal breakdown and superficial scald of 'Red Delicious' apples during storage. Scientia Hortic., 9: 245--249. The 2-year investigation involved storing fruit samples from each tree in a trial of 8 rootstocks with the locally selected 'Lalla Red Delicious' to see how the storage characteristics were modified by rootstock and/or calcium sprays. The 6 spray applications of calcium made a significant reduction in the incidence of internal breakdown in both years, although the magnitude of the response varied from rootstock to rootstock in 1976. There were no significant rootstock effects in 1975, and in 1976 they were eliminated where calcium sprays were used. In the absence of calcium sprays in 1976, apples from 'M. 16' produced significantly more internal breakdown than those from any of the other stocks, with 'MM. 107' producing the second highest level. At the other end of the scale, apples from 'MM. 110' had the lowest incidence, closely followed by 'M. 1.' The remaining 4 stocks ('11 immune', 'M.13', 'M.25' and 'Seedling') gave intermediate readings and were not significantly different from each other. The calcium spray treatments also significantly reduced the incidence of superficial scald with all rootstocks. The main rootstock effect observed was that apples from 'MM. 110' and 'M. 1' had significantly less scald than from 5 of the other 6 rootstocks.
INTRODUCTION T w o o f the m o s t i m p o r t a n t aspects o f q u a l i t y o f ' R e d Delicious' g r o w n u n d e r Australian c o n d i t i o n s are susceptibility to the storage disorders "superficial s c a l d " and " i n t e r n a l b r e a k d o w n " . I n f o r m a t i o n is n e e d e d o n w h e t h e r r o o t s t o c k s a f f e c t either o r b o t h . A c c o r d i n g t o the review b y Fidler et al. ( 1 9 7 3 ) , Keijer and Dijksterhuis ( 1 9 5 6 ) were u n a b l e to d e t e c t a n y differences in the incidence o f scald in ' G o l d e n R e i n e t t e ' f r o m trees o n 'M. 1' and 'M. 4 ' r o o t s t o c k s . H o w e v e r , the susceptibility o f ' B r a m l e y ' s Seedling' t o b r e a k d o w n varied a c c o r d i n g to ro6+,stocks ( K i d d and West, 1 9 3 4 ; Wallace, 1953; S c h u b e r t , 1967). More
246
recently it has been shown that applied calcium reduces breakdown in apples (Mason, 1970; Mason and Porritt, 1972; Bangerth, 1973; Blank, 1975; Shear, 1975). Lidster et al. {1975) found a very high correlation between fruit calcium levels and 'Spartan' apple breakdown but no significant relationship between rootstock type and breakdown. A trial consisting of 8 rootstocks designed to study the field performance of the locally selected 'Lalla Red Delicious' was planted in 1959 at the Huon Horticultural Research Station. The 1975 and 1976 crops were chosen by the authors to see how the storage characteristics were modified by rootstock and/or calcium sprays. METHOD The field trial consisted of 8 replicates of 2-tree plots on rootstocks 'M. 1', '11 immune', 'M. 13', 'M. 16', 'M. 25', 'MM. 107', 'MM. 110' and 'Sturmer Seedling'. The trees were planted at 6.1 X 6.1 m spacing using a Latin square design. In each of the 2 seasons studied, 1 tree in each pair received 6 calcium sprays between mid-November and the end of February. In 1974/ 75 calcium nitrate was used, whereas in 1975/76 calcium chloride was used. The first 2 spray applications were at 0.5 kg/100 litres, the third at 0.8 kg/ 100 litres and the last 3 at 1 kg/100 litres. All trees in the trial were harvested individually during the last week in March each year. For each tree a 3-box sample (approximately 350 apples) was taken at random when the fruit was passed over a grader. These samples were then stored at 1--2°C in a specially constructed blanket type cool r o o m as described by Atkins (1973). This type of cool room ensures humidities are in excess of 85%. After 12 weeks storage, the samples were placed in a constant temperature room where temperature and relative humidity were maintained at 25°C and 90--95%, respectively. Following 10 days under these conditions, the fruit was examined for the disorders superficial scald and internal breakdown. The percentages of each disorder were transformed prior to analysis of variance using the arcsine square root transformation. The decision to use transformed values was based on a plot of residual values against expected values according to Draper and Smith (1966). RESULTS AND DISCUSSION Internal breakdown. - - The 6 spray applications of calcium made a significant reduction in the incidence of internal breakdown in both years. However, the magnitude of the response to calcium sprays varied from rootstock to rootstock in 1976 (Table I) and appeared to be related to the level of incidence of the disorder in unsprayed trees. This was responsible for the statistically significant interaction between rootstock and spray treatment. There were no significant rootstock effects in 1975, whilst in 1976 they
247
were eliminated where calcium sprays were used. In the absence of calcium sprays in 1976, apples f r o m 'M. 16' had significantly more internal breakdown than those from any o f the ot her stocks. At the o t h e r end of the scale, 'MM. 110' pr oduced fruit with the lowest incidence o f this storage disorder and was significantly different from all o t h er stocks with the e xc e pt i on of 'M. 1'. Apples from 'MM. 107' had the second highest a m o u n t of internal breakdown, being significantly different from the majority of other stocks. The remaining 4 root st ocks ('11 immune', 'M. 13', 'M. 25' and 'Seedling') gave intermediate readings n o t significantly different from each other. The 1976 results generally agree with observations on the same block in 1974 prior to the use of calcium sprays (O'Loughlin and Jotic, unpublished data, 1974). The results o f the present trial indicate that calcium sprays exert ed a far greater influence on the level of internal breakdown than did the range of r o o ts to ck s included in the experiment. This can be related to previously r ep o r ted results (Mason, 1970; Mason and Porritt, 1972; Blank, 1975; Shear, 1975) which showed t ha t applied calcium greatly reduces the a m o u n t of breakdown in apples. However, when calcium sprays were omitted, there were some significant differences between root st ocks in susceptibility of the fruit to internal breakdown. These could n o t be attributed solely to differences in mean fruit weight, as in 1976 'M. 16' had the highest incidence o f the disorder although its mean fruit weight {129.9 g) was n o t significantly different f r o m that o f 'M. 2', 'M. 25', 'Seedling', 'MM. 107' and '11 TABLE 1 Incidence of internal breakdown in 1975 and 1976 as arcsine square root percentages; original percentages in brackets Rootstock
1975 Calcium spray
Nil spray
1976 Calcium
Nil
spray
spray
MM. 110 M. 1 11 immune M. 13
2.5 2.5 3.0 2.5
(0.6) (0.4) (0.5) (0.4)
10.4 7.3 9.6 12.2
(5.8) (2.6) (4.0) (5.4)
0.4 0.4 0 0.4
(0.04) (0.04) (0) (0.04)
Seedling M. 25 MM. 107 M. 16
4.2 3.5 3.3 2.1
(0.9) (0.6) (0.7) (0.3)
6.5 9.5 9.4 10.8
(2.5) (3.4) (3.9) (3.9)
3.0 1.3 1.8 2.3
(0.4) (0.2) (0.3) (0.3)
Mean
2.9
9.5
1.2
4.9 6.4 8.9 9.8 10.9 12.0 14.2 17.9
(0.9) (1.5) (2.6) (3.3) (4.0) (4.7) (6.7) (10.0)
10.6
1975 L.S.D. ( P = 0.05): (a) between spray treatments = 1.8; (b) between rootstocks = N.S. (S.E.D. = 2.0).
1976 L.S.D. (P = 0.05): (a) For comparisons between rootstocks for an individual spray treatment ffi 3.1; (b) For comparisons between spray treatments for an individual rootstock = 3.2.
248
immune' (129.3--134.0 g). However, 'MM' 110' (123.9 g) and 'M. 1' (120.1 g) which had least internal breakdown had significantly lower mean fruit weights than the other 6 rootstocks. R o o t s t o c k effects on breakdown have been reported previously (Kidd and West, 1934; Wallace, 1953; Schubert, 1967). Possibly seasonal factors were responsible for the absence of a rootstock effect in 1975. Another way of summarising the results is to suggest that calcium sprays should be used for all 'Lalla Red Delicious', especially when grown on 'M. 16' or 'MM. 107'. Superficial s c a l d . - - In 1975, the levels of superficial scald were too low to be analysed due to the number of zero values. However, in 1976, the 6 spray applications of calcium produced a large (statistically significant) reduction in the incidence of scald (Table 2). This had previously been reported by Blank (1975), who found that spraying fruit 5 times before harvest with calcium chloride solutions gave considerable reductions in the incidence of superficial scald. As well as the spray effect, there were significant rootstock effects with apples from 'MM. 110' and 'M. 1' having significantly less scald than fruit from 5 of the other 6 stocks. However, these calcium and rootstock effects would be of very limited commercial importance as scald in 'Delicious' grown in Australia can usually be prevented completely by post-harvest dips of diphenylamine (Smock, 1957; Hall, 1972; Tugwell, 1975).
TABLE 2
Incidence of superficial scald in 1976 as arcsine square root percentages; original percentages in brackets Rootstock
Calcium spray
Nil spray
Mean
MM. 110 M. 1 11 immune M. 13 M. 16 M. 25 MM. 107 Seedling Mean
3.0 3.6 4.6 5.7 6.8 8.2 9.8 7.2 6.1
9.6 13.9 18.6 20.7 20.2 20.9 22.5 26.4 19.1
6.3 8.7 11.6 13.2 13.5 14.6 16.2 16.8
(0.5) (0.5) (0.9) (1.4) (1.9) (3.3) (4.3) (2.6)
(3.4) (6.3) (12.0) (13.7) (12.4) (13.8) (16.5) (21.7)
L.S.D. (P = 0.05): (a) between spray treatments = 2.1; (b) between rootstocks = 4.3.
ACKNOWLEDGEMENTS
The authors acknowledge the assistance of Messrs. L. Zantuck, M. Priest, M. Oakford and G. Adams in the conduct of their trials. The advice of Mr. P. Gillis, Biometrician, on the analysis of the trials was greatly appreciated.
249
REFERENCES Atkins, R., 1973. Controlled atmosphere stores for fruit.C.S.I.R.O. Food Res. Q., 33: 75--80. Bangerth, F., 1973. Investigations upon calcium related physiological disorders. Phytopathol. Z., 77: 20--37. Blank, H.G., 1975. Studies on the control of superficial scald on the apple cultivar Holsteiner Cox. Mitt. Obstbauversuchsringes des Alten Landes, 30: 229--236. Draper, N.R. and Smith, H., 1966. In: Examination of residuals. Applied Regression Analyses, Chap. 3, Wiley, New York, 407 pp. Fidler, J.C., Wilkinson, B.G., Edney, K.L. and Sharpies, R.O., 1973. The biology of apple and pear storage. Res. Rev. No. 3., Commonw. Bur. Hortic. Plant. Crops. (G.B.), 235 pp., 177--178. Hall, E.G., 1972. Cool storage of apples and pears - - directions for practical scald control. C.S.I.R.O. F o o d Res. Q., 32: 3 3 - 3 8 . Keijer, E.J. and Dijksterhuis, H.P., 1956. Bewaarziekten bij appels. De invloed van verschillende schurftbestrijdingsmiddelen. I. Onderzoek naar de oorzaken van stip. Meded. Dir. Tuinbouw (Neth.), 19: 396--400, 406. Kidd, F. and West, C., 1934. The effects of rootstock on the keeping quality of Bramley's Seedling apples. Rep. Food. Invest. Board for 1933, 204--205. Lidster, P.D., Porritt, S.W., Eaton, G.W. and Mason, J., 1975. Spartan apple breakdown as effected by orchard factors, nutrient content and fruit quality. Can. J. Plant Sci., 55: 443--446. Mason, J.L., 1970. Breakdown in Spartan apples. Can. Agric., 15: 30--31. Mason, J.L. and Porritt, S.W., 1972. Calcium concentrate sprays control Spartan apple breakdown. Can. Agric., 17: 28--29. Schubert, E., 1967. Sind Lagerverluste durch Fleischbr~une beim Apfel vermeidbar? Obstbau (East Berlin), 7: 184--186. Shear, C.B., 1975. Calcium nutrition and quality in fruitcrops. C o m m u n . Soil Sci. Plant Anal., 6: 233--244. Smock, R.M., 1957. A comparison of treatments for control of the apple scald disease. Proc. Am. Soc. Hortic. Sci., 69: 91--100. Tugwell, B.L., 1975. Some common storage disorders of apples and pears. Agric. Dept. South Austr. Bull., No. 478. Wallace, T., 1953. Some effects of orchard factors on the quality and storage properties of apples. Sci. Fruit, Univ. Bristol, pp. 140--161.
245
THE RELATIVE EFFECTS OF ROOTSTOCKS AND CALCIUM SPRAYS ON THE APPEARANCE OF INTERNAL BREAKDOWN AND SUPERFICIAL SCALD OF ' R E D D E L I C I O U S ' APPLES D U R I N G S T O R A G E
J.B. O'LOUGHLIN and P. JOTIC Department of Agriculture, New Town Research Laboratories, St. John's Avenue, New Town, Tasmania, 7 00~ (Australia)
(Received 3 February 1978)
ABSTRACT O'I~ughlin, J.B. and Jotic, P., 1978. The relative effects of rootstocks and calcium sprays on the appearance of internal breakdown and superficial scald of 'Red Delicious' apples during storage. Scientia Hortic., 9: 245--249. The 2-year investigation involved storing fruit samples from each tree in a trial of 8 rootstocks with the locally selected 'Lalla Red Delicious' to see how the storage characteristics were modified by rootstock and/or calcium sprays. The 6 spray applications of calcium made a significant reduction in the incidence of internal breakdown in both years, although the magnitude of the response varied from rootstock to rootstock in 1976. There were no significant rootstock effects in 1975, and in 1976 they were eliminated where calcium sprays were used. In the absence of calcium sprays in 1976, apples from 'M. 16' produced significantly more internal breakdown than those from any of the other stocks, with 'MM. 107' producing the second highest level. At the other end of the scale, apples from 'MM. 110' had the lowest incidence, closely followed by 'M. 1.' The remaining 4 stocks ('11 immune', 'M.13', 'M.25' and 'Seedling') gave intermediate readings and were not significantly different from each other. The calcium spray treatments also significantly reduced the incidence of superficial scald with all rootstocks. The main rootstock effect observed was that apples from 'MM. 110' and 'M. 1' had significantly less scald than from 5 of the other 6 rootstocks.
INTRODUCTION T w o o f the m o s t i m p o r t a n t aspects o f q u a l i t y o f ' R e d Delicious' g r o w n u n d e r Australian c o n d i t i o n s are susceptibility to the storage disorders "superficial s c a l d " and " i n t e r n a l b r e a k d o w n " . I n f o r m a t i o n is n e e d e d o n w h e t h e r r o o t s t o c k s a f f e c t either o r b o t h . A c c o r d i n g t o the review b y Fidler et al. ( 1 9 7 3 ) , Keijer and Dijksterhuis ( 1 9 5 6 ) were u n a b l e to d e t e c t a n y differences in the incidence o f scald in ' G o l d e n R e i n e t t e ' f r o m trees o n 'M. 1' and 'M. 4 ' r o o t s t o c k s . H o w e v e r , the susceptibility o f ' B r a m l e y ' s Seedling' t o b r e a k d o w n varied a c c o r d i n g to ro6+,stocks ( K i d d and West, 1 9 3 4 ; Wallace, 1953; S c h u b e r t , 1967). More
246
recently it has been shown that applied calcium reduces breakdown in apples (Mason, 1970; Mason and Porritt, 1972; Bangerth, 1973; Blank, 1975; Shear, 1975). Lidster et al. {1975) found a very high correlation between fruit calcium levels and 'Spartan' apple breakdown but no significant relationship between rootstock type and breakdown. A trial consisting of 8 rootstocks designed to study the field performance of the locally selected 'Lalla Red Delicious' was planted in 1959 at the Huon Horticultural Research Station. The 1975 and 1976 crops were chosen by the authors to see how the storage characteristics were modified by rootstock and/or calcium sprays. METHOD The field trial consisted of 8 replicates of 2-tree plots on rootstocks 'M. 1', '11 immune', 'M. 13', 'M. 16', 'M. 25', 'MM. 107', 'MM. 110' and 'Sturmer Seedling'. The trees were planted at 6.1 X 6.1 m spacing using a Latin square design. In each of the 2 seasons studied, 1 tree in each pair received 6 calcium sprays between mid-November and the end of February. In 1974/ 75 calcium nitrate was used, whereas in 1975/76 calcium chloride was used. The first 2 spray applications were at 0.5 kg/100 litres, the third at 0.8 kg/ 100 litres and the last 3 at 1 kg/100 litres. All trees in the trial were harvested individually during the last week in March each year. For each tree a 3-box sample (approximately 350 apples) was taken at random when the fruit was passed over a grader. These samples were then stored at 1--2°C in a specially constructed blanket type cool r o o m as described by Atkins (1973). This type of cool room ensures humidities are in excess of 85%. After 12 weeks storage, the samples were placed in a constant temperature room where temperature and relative humidity were maintained at 25°C and 90--95%, respectively. Following 10 days under these conditions, the fruit was examined for the disorders superficial scald and internal breakdown. The percentages of each disorder were transformed prior to analysis of variance using the arcsine square root transformation. The decision to use transformed values was based on a plot of residual values against expected values according to Draper and Smith (1966). RESULTS AND DISCUSSION Internal breakdown. - - The 6 spray applications of calcium made a significant reduction in the incidence of internal breakdown in both years. However, the magnitude of the response to calcium sprays varied from rootstock to rootstock in 1976 (Table I) and appeared to be related to the level of incidence of the disorder in unsprayed trees. This was responsible for the statistically significant interaction between rootstock and spray treatment. There were no significant rootstock effects in 1975, whilst in 1976 they
247
were eliminated where calcium sprays were used. In the absence of calcium sprays in 1976, apples f r o m 'M. 16' had significantly more internal breakdown than those from any o f the ot her stocks. At the o t h e r end of the scale, 'MM. 110' pr oduced fruit with the lowest incidence o f this storage disorder and was significantly different from all o t h er stocks with the e xc e pt i on of 'M. 1'. Apples from 'MM. 107' had the second highest a m o u n t of internal breakdown, being significantly different from the majority of other stocks. The remaining 4 root st ocks ('11 immune', 'M. 13', 'M. 25' and 'Seedling') gave intermediate readings n o t significantly different from each other. The 1976 results generally agree with observations on the same block in 1974 prior to the use of calcium sprays (O'Loughlin and Jotic, unpublished data, 1974). The results o f the present trial indicate that calcium sprays exert ed a far greater influence on the level of internal breakdown than did the range of r o o ts to ck s included in the experiment. This can be related to previously r ep o r ted results (Mason, 1970; Mason and Porritt, 1972; Blank, 1975; Shear, 1975) which showed t ha t applied calcium greatly reduces the a m o u n t of breakdown in apples. However, when calcium sprays were omitted, there were some significant differences between root st ocks in susceptibility of the fruit to internal breakdown. These could n o t be attributed solely to differences in mean fruit weight, as in 1976 'M. 16' had the highest incidence o f the disorder although its mean fruit weight {129.9 g) was n o t significantly different f r o m that o f 'M. 2', 'M. 25', 'Seedling', 'MM. 107' and '11 TABLE 1 Incidence of internal breakdown in 1975 and 1976 as arcsine square root percentages; original percentages in brackets Rootstock
1975 Calcium spray
Nil spray
1976 Calcium
Nil
spray
spray
MM. 110 M. 1 11 immune M. 13
2.5 2.5 3.0 2.5
(0.6) (0.4) (0.5) (0.4)
10.4 7.3 9.6 12.2
(5.8) (2.6) (4.0) (5.4)
0.4 0.4 0 0.4
(0.04) (0.04) (0) (0.04)
Seedling M. 25 MM. 107 M. 16
4.2 3.5 3.3 2.1
(0.9) (0.6) (0.7) (0.3)
6.5 9.5 9.4 10.8
(2.5) (3.4) (3.9) (3.9)
3.0 1.3 1.8 2.3
(0.4) (0.2) (0.3) (0.3)
Mean
2.9
9.5
1.2
4.9 6.4 8.9 9.8 10.9 12.0 14.2 17.9
(0.9) (1.5) (2.6) (3.3) (4.0) (4.7) (6.7) (10.0)
10.6
1975 L.S.D. ( P = 0.05): (a) between spray treatments = 1.8; (b) between rootstocks = N.S. (S.E.D. = 2.0).
1976 L.S.D. (P = 0.05): (a) For comparisons between rootstocks for an individual spray treatment ffi 3.1; (b) For comparisons between spray treatments for an individual rootstock = 3.2.
248
immune' (129.3--134.0 g). However, 'MM' 110' (123.9 g) and 'M. 1' (120.1 g) which had least internal breakdown had significantly lower mean fruit weights than the other 6 rootstocks. R o o t s t o c k effects on breakdown have been reported previously (Kidd and West, 1934; Wallace, 1953; Schubert, 1967). Possibly seasonal factors were responsible for the absence of a rootstock effect in 1975. Another way of summarising the results is to suggest that calcium sprays should be used for all 'Lalla Red Delicious', especially when grown on 'M. 16' or 'MM. 107'. Superficial s c a l d . - - In 1975, the levels of superficial scald were too low to be analysed due to the number of zero values. However, in 1976, the 6 spray applications of calcium produced a large (statistically significant) reduction in the incidence of scald (Table 2). This had previously been reported by Blank (1975), who found that spraying fruit 5 times before harvest with calcium chloride solutions gave considerable reductions in the incidence of superficial scald. As well as the spray effect, there were significant rootstock effects with apples from 'MM. 110' and 'M. 1' having significantly less scald than fruit from 5 of the other 6 stocks. However, these calcium and rootstock effects would be of very limited commercial importance as scald in 'Delicious' grown in Australia can usually be prevented completely by post-harvest dips of diphenylamine (Smock, 1957; Hall, 1972; Tugwell, 1975).
TABLE 2
Incidence of superficial scald in 1976 as arcsine square root percentages; original percentages in brackets Rootstock
Calcium spray
Nil spray
Mean
MM. 110 M. 1 11 immune M. 13 M. 16 M. 25 MM. 107 Seedling Mean
3.0 3.6 4.6 5.7 6.8 8.2 9.8 7.2 6.1
9.6 13.9 18.6 20.7 20.2 20.9 22.5 26.4 19.1
6.3 8.7 11.6 13.2 13.5 14.6 16.2 16.8
(0.5) (0.5) (0.9) (1.4) (1.9) (3.3) (4.3) (2.6)
(3.4) (6.3) (12.0) (13.7) (12.4) (13.8) (16.5) (21.7)
L.S.D. (P = 0.05): (a) between spray treatments = 2.1; (b) between rootstocks = 4.3.
ACKNOWLEDGEMENTS
The authors acknowledge the assistance of Messrs. L. Zantuck, M. Priest, M. Oakford and G. Adams in the conduct of their trials. The advice of Mr. P. Gillis, Biometrician, on the analysis of the trials was greatly appreciated.
249
REFERENCES Atkins, R., 1973. Controlled atmosphere stores for fruit.C.S.I.R.O. Food Res. Q., 33: 75--80. Bangerth, F., 1973. Investigations upon calcium related physiological disorders. Phytopathol. Z., 77: 20--37. Blank, H.G., 1975. Studies on the control of superficial scald on the apple cultivar Holsteiner Cox. Mitt. Obstbauversuchsringes des Alten Landes, 30: 229--236. Draper, N.R. and Smith, H., 1966. In: Examination of residuals. Applied Regression Analyses, Chap. 3, Wiley, New York, 407 pp. Fidler, J.C., Wilkinson, B.G., Edney, K.L. and Sharpies, R.O., 1973. The biology of apple and pear storage. Res. Rev. No. 3., Commonw. Bur. Hortic. Plant. Crops. (G.B.), 235 pp., 177--178. Hall, E.G., 1972. Cool storage of apples and pears - - directions for practical scald control. C.S.I.R.O. F o o d Res. Q., 32: 3 3 - 3 8 . Keijer, E.J. and Dijksterhuis, H.P., 1956. Bewaarziekten bij appels. De invloed van verschillende schurftbestrijdingsmiddelen. I. Onderzoek naar de oorzaken van stip. Meded. Dir. Tuinbouw (Neth.), 19: 396--400, 406. Kidd, F. and West, C., 1934. The effects of rootstock on the keeping quality of Bramley's Seedling apples. Rep. Food. Invest. Board for 1933, 204--205. Lidster, P.D., Porritt, S.W., Eaton, G.W. and Mason, J., 1975. Spartan apple breakdown as effected by orchard factors, nutrient content and fruit quality. Can. J. Plant Sci., 55: 443--446. Mason, J.L., 1970. Breakdown in Spartan apples. Can. Agric., 15: 30--31. Mason, J.L. and Porritt, S.W., 1972. Calcium concentrate sprays control Spartan apple breakdown. Can. Agric., 17: 28--29. Schubert, E., 1967. Sind Lagerverluste durch Fleischbr~une beim Apfel vermeidbar? Obstbau (East Berlin), 7: 184--186. Shear, C.B., 1975. Calcium nutrition and quality in fruitcrops. C o m m u n . Soil Sci. Plant Anal., 6: 233--244. Smock, R.M., 1957. A comparison of treatments for control of the apple scald disease. Proc. Am. Soc. Hortic. Sci., 69: 91--100. Tugwell, B.L., 1975. Some common storage disorders of apples and pears. Agric. Dept. South Austr. Bull., No. 478. Wallace, T., 1953. Some effects of orchard factors on the quality and storage properties of apples. Sci. Fruit, Univ. Bristol, pp. 140--161.