Prediction of apple fruit quality using preharvest mineral nutrients

Leaf mineral analysis has been a useful tool for diagnosis of apple tree (Malus x domestica Bork.) deficiencies for several decades. However, leaf minerals alone cannot precisely predict many of the fruit postharvest disorders. Therefore, fruit analysis alone or in combination with leaf analysis are used for a more precise prediction of fruit quality. The authors have been developed several prediction models for prediction of apple fruit quality over the last several years. Models developed within a given year, can predict apple fruit quality attributes for that year, but may not strongly predict quality attributes in different years. To solve this problem, a ranking of major minerals, such as calcium (Ca) and nitrogen (N) has been developed that can predict apple fruit quality within a year and between years. In these trials magnesium (Mg) infiltration was also used into fruit to artificially induce bitter pit, and based on the degree of bitter pit occurrence, predict the potential for postharvest bitter pit development. In these studies, increase in fruit N was always negatively associated with fruit yellow or red color and increase in fruit Ca was negatively associated with bitter pit but was positively associated with fruit firmness. Apple fruits with greater N concentrations had greater ethylene concentrations and respiration rates. In this article, an overview of prediction studies from these authors and other researchers are discussed.