- 1"S 



COMPARISON OF SOME FRUIT CHARACTERISTICS OF 'MCINTOSH' 

 APPLES GROWN ON SEEDLING AND M7 ROOTSTOCKS 



Sarah A. Weis, Mack Drake 



and William J. Bramlage 



Department of Plant and Soil Sciences 



Post-storage senescent breakdown (breakdown^ of apple causes signifi- 

 cant fruit loss, most of which occurs after the fruit have been distributed. 

 It can be difficult for the grower or packer of the fruit to anticipate the 

 breakdown potential of a lot of fruit at the time of packing. While many 

 apple growers learn through experience which areas of an orchard produce ^he 

 fruit which keep best, it would be useful to improve methods of predicting 

 breakdown potential . 



From \0T^ to l*^?? we conducted surveys in orchards throughout 

 Massachusetts to see how fruit mineral composition affected breakdown inci- 

 dence in Mcintosh apples. Most of the trees in those surveys were growing 

 either on seedling or M7 rootstocks. The most important measured contribu- 

 tion to breakdown incidence was calcium deficiency. 



Another factor, in addition to fruit mineral concentration, which may 

 influence the susceptibl ity of fruit to breakdown is rootstock. Some people 

 may have suspected that fruit grown on trees of different rootstocks have 

 different storage characteristics. In any given orchard such suspected dif- 

 ferences may be the result of block differences in soil, exposure, eleva- 

 tion, etc., or they may actually be due to differences in rootstock 

 characteristics. In a larger study, such as we have done, differences 

 attributed to location can be minimized. For the comparision of mineral 

 concentrations and breakdown incidence between rootstocks, data from the 

 above surveys of Mcintosh grown on seedling or M"' rootstocks were used. 



Calcium (Ca\ magnesium ^Mg), potassium 'K\ phosphorus 'P), and nitro- 

 gen fN^ concentrations, and size in grams/fruit, were measured two weeks 

 before the beginning of commerical harvest each year. Twenty-five fruit 

 were analyzed from each orchard block surveyed. At the beginning of com- 

 merical harvest two bushels of fruit were picked from each block. One 

 bushel was stored S months in QOC air, the other for 8 months in controlled 

 atmosphere (CA^ at ?o, "^"^ 0?, ^^ COp at the Horticulture Research Center 

 ^HRC) in Belchertown, MA. Ai^ter fruit were removed from storage, they were 

 left at room temperature (approx. ""^o^ for a week before percent of fruit 

 with breakdown was assessed. In l^Bl the post-storage room temperature was 

 about '^Do. hence, there was much higher breakdown incidence in 1^81. 



Table 1 shows results of the ^-year survey. Looking first at the ele- 

 ments measured, no differences between fruit from seedling and M'' trees were 

 found for Ca , K, P, or N. In l^R? and 1<^S3 Mg concentration of fruit from 

 M'' trees was lower than that from seedling trees, but, at the levels 

 observed, Mg concentration has not been found to influence breakdown. Fruit 

 size, which affects breakdown positively, was the same for seedling and M7 

 rootstocks. After CA storage fruit from M7 trees, did have more breakdown. 

 This was statistically significant at odds of IQ;! in l^"'" and 1°^? and at 

 odds of Q:l in 1°80. The difference was insignificant in IQ81. Although 

 breakdown differences after air storage were insignificant statistically, 

 percent breakdown was greater on fruit from M7 blocks "^ years out of ^. 



