Relationships Between Leaf and Fruit Nutrients and Fruit Quality Attributes in Golden Smoothee Apples Using Multivariate Regression Techniques

The relationships between leaf and fruit nutrients in “Golden Smoothee” apples (Malus domestica Borkh. L) were analyzed using partial least squares regressions (PLS). The aim of the study is to identify the most relevant concentration nutrients for fruit quality in leaves (l) and fruits (f), and to work out the correlation among them and also in relation with some apple fruit quality attributes. The majority of leaf mineral concentrations [nitrogen (N), calcium (Ca), magnesium (Mg), and boron (B)] display a negative correlation with fruit N at harvest. There are positive correlations between fruit minerals [phosphorus (P), potassium (K), Mg, and boron (B)] and fruit N concentration, except for fruit Ca, which correlates negatively with fruit N. The results obtained suggest that leaf K concentration appears to be highly correlated positively with fruit K and P concentrations at harvest. Fruit B content displays a highly negative regression coefficient with leaf B concentration. Leaf Ca seems to exhibit no clear relationship with fruit Ca at harvest and this manifests as a negative correlation with many macronutrients in fruit, such as N, P, and K. These results suggest that leaf K, Ca, and Mg concentrations are good indicators for predicting the fruit K at harvest, with the leaf K influencing this positively, while leaf Ca and Mg exercise a highly negative influence. Fruit quality attributes, such as fruit acidity, are positively influenced by K and P nutrients, both in the leaf and fruit. Fruit firmness shows a positive correlation with the fruit Ca content and bitter pit incidence correlates negatively with this nutrient concentration.