INFLUENCE OF PREHARVEST CALCIUM TREATMENTS ON POSTHARVEST QUALITY OF SOME ESTONIAN APPLE CULTIVARS

Abstract

Current research was conducted with apple (Malus domestica) cultivars Liivi Kuldrenett, Krameri tuvioun, Talvenauding and Tellissaare at Estonian Agricultural University during 2002-2003. The aim of the research was to find out the influence of preharvest calcium sprays from different sources, CaCl 2 and Ca (NO 3 ) 2 , on postharvest quality and storability of apples in normal atmosphere. Storage period for 'Liivi Kuldrenett' and 'Krameri tuvioun' was 4 months, for 'Talvenauding' 6 months and for 'Tellissaare' 7 months. Following variables were measured after harvest and monthly during storage: loss of marketable yield, content of fruit nitrogen and calcium, dry matter, soluble solids and titratable acids. Main physiological disorders such as bitter pit, physiological spot and superficial scald were scored visually every month. Average effect of calcium treatment on the amount of spoiled fruits at the end of the storage was not significant, but in most cases effect of cultivar was remarkable. Content of fruit soluble solids, titratable acids and dry matter after harvest was significantly reduced by calcium treatment and had values from 12.8 to 11.7% for soluble solids, from 0.79 to 0.67% for titratable acids and from 13.1 to 12.3% for dry matter in control and calcium-treated variants, respectively. Bitter pit incidence appeared mostly during first two months of storage and was significantly reduced by calcium treatment, but incidence of physiological spot in calcium-treated 'Krameri tuvioun' was increased. Preharvest fertilization with CaCl 2 and Ca(NO 3 ) 2 significantly increased both calcium and nitrogen content in apple fruits. Correlations between quality characteristics after harvest and incidence of physiological disorders are presented and discussed.