Predicting the Occurrence of Poststorage Disorders of ‘McIntosh’ Apples from Preharvest Mineral Analyses

In a 4-year study of the relationships between Ca, K, P, Mg, and N concentrations in ‘McIntosh’ apples at harvest and the quality of fruit after storage, Ca was the most variable element among samples within seasons and was the element most consistently related to disorders, being negatively correlated with senescent breakdown, rot, and scald. No element was correlated significantly with fruit firmness at harvest or after storage. Susceptibility of orchard lots of fruit to breakdown could be predicted from mineral analyses of fruit 2 weeks before harvest. An arbitrary scoring system incorporating all 5 elements was correct 69% of the time in identifying lots with high or low potentials for breakdown, but the middle range of scores was not closely related to breakdown potential. A regression equation was developed relating only Ca concentration in fruit at harvest with occurrence of breakdown after storage. This equation represented samples either stored in 0°C air for 5 months or in 3° CA storage for 8 to 9 months, and also represented samples taken in 2 different years. This equation was a better predictor of breakdown during storage than was the mineral scoring system, and we propose that such an equation could be used to predict storage potential for ‘McIntosh’ apples.