Abstract
Several studies have focused on the improvement of strawberry (Fragaria ×ananassa Duch.) fruit firmness with additional calcium (Ca) applications. These studies found conflicting results for additions of Ca when it is applied as soil-applied gypsum or various foliar formulations. Because limited information exists on the association between fruit firmness and tissue Ca concentration in commercial strawberry cultivars, the objective of this study was to determine if leaf or fruit Ca concentration is a reliable predictor of fruit firmness. Leaf and fruit samples for Ca concentration and firmness measurements were determined in Feb. and Mar. 2004 on seven cultivars and correlations were conducted using Pearson’s correlation coefficient. Ca concentration and fruit firmness was significantly different among cultivars. Leaf Ca concentrations ranged between 8,390 (‘Camarosa’) and 11,986 (‘Winter Dawn’) mg·kg–1. Fruit Ca concentrations ranged between 1,572 (‘Winter Dawn’) and 2,550 (‘Sweet Charlie’) mg·kg–1. ‘Treasure’ had the firmest fruits (1.23 N) and ‘Sweet Charlie’ the least firm (0.72 N). There was a wide range in r-values among the correlations, but ‘Camarosa’ had the highest average correlation between fruit Ca concentration and firmness (r = +0.67) and ‘Treasure’ for leaf Ca concentration and fruit firmness (r = +0.29). Based upon this study, no relationship was found between fruit firmness and Ca concentration. Therefore, the practice of applying supplemental Ca to strawberry plants during its normal growing season may not be beneficial to increasing fruit firmness. Moreover, Ca concentration within strawberry plants should not be used as a predictor of fruit firmness or to substitute for firm fruited cultivars used in production in the selection of lines during breeding.
