Variation between apple fruits and its relation to keeping quality. 1. Within-tree variation.

Abstract

Variation within trees of diameter, colour, firmness, starch conversion, total acid, and soluble solids of fruit was examined for branches of different aspect for four varieties of apples and at different stages of maturity for one of them. Incidence of the storage disorders pit and breakdown in Cox Jonathan spot and deep scald in Jonathan, and pit in Cleopatra and Sturmer was examined in quarter-inch size groups within trees. The data revealed that the frequency distribution of all variables except starch conversion were of the unimodal, symmetric, or slightly skew type. Starch conversion showed strong positive skewness at low values and strong negative skewness at high values, which is characteristic of variables which have defined limits. As fruit matured, variability increased, except for starch conversion, which decreased. For three varieties, but not for a fourth, the pattern of correlation between variables within branches resembled the pattern obtained by correlating the variables at different stages of maturity of fruit from one source, but heterogeneity between branches weakened the correlation for the tree as a whole. The pattern of means in relation to aspect was not necessarily the same for two adjacent trees or for the same tree at different maturities, indicating that aspect as such was not the cause of heterogeneity within a tree but that the branches behaved as organic units. Size was correlated within a tree with incidence of the disorders pit and breakdown, but while the relationship appeared to be linear over the restricted size range there was no justification for extrapolating this relationship. There was evidence of between-branch variation in disorder incidence.