Mineral Analysis from Corkspotted and Normal `Anjou' Pear Fruit

Abstract

Relationships between mineral content and corkspot in `Anjou' pears (Pyrus communis) were evaluated in 1985 and 1986. Although there were no significant relationships between mean preharvest fruit mineraI content and corkspot incidence, the postharvest mineral concentrations of corkspotted and normal fruit were markedly different. Corkspotted and normal pear fruit had different Ca and N : Ca ratios in all types of subsamples (peels, opposing tangential slices with peels, opposing tangential slices without peels, cortical tissue plugs from the area next to the core, cortical tissue plugs from the area just inside of the peel, and the cores including seed), based on either dry or fresh weight. The dry-weight basis also revealed differences in Mg concentrations in both years and in B and K concentrations in 1986. Peel concentrations correlated with other tissues and were the easiest subsample to process. Corkspot was absent in either year, with a peel N: Ca ratio below 6.3. A computer model used mean Ca concentrations and standard deviations to estimate the percentage of pears in each orchard that were less than a given threshold level. When the overall average percentage of arbitrarily defined low-Ca pears was small (< 10%), it was difficult to predict the actual number of low-Ca pears from mean Ca concentrations. Therefore, it may not be realistic to expect strong correlations between mean Ca concentration and the incidence of disorders commonly encountered in Hood River, Ore. This situation occurred even when Ca concentrations of disordered and normal pears clearly differed.