Effects of Preharvest Calcium Sprays on Yield, Quality and Mineral Nutrient Concentrations of ‘Asgari’ Table Grape

Abstract

Effects of three preharvest sprays of calcium chloride (CaCl2) on fruit quality, yield, and mineral content in ‘Asgari’ table grape (Vitis vinifera) were studied. Calcium sprays were made at rates of 0%, 0.8%, 1.2%, 1.6%, and 2% w/v as T0, T1, T2, T3, and T4, respectively. Applications were made at fruit set, early pre-bunch closure, and late bunch closure. Fruit analyses showed that Ca partitioning in the various parts of the fruit was not proportional to the levels of Ca application. The rate of Ca accumulation in the berry during the berry development followed a sigmoid pattern in all treatments. The rate of Ca accumulation depended on both the growth phase and the level of Ca applied. The highest rate was recorded at 60 days after anthesis in the high Ca (T4) treatment. Calcium accumulation in the berry ceased after 80 days past anthesis (beginning of veraison) in all treatments, while Ca redistributed from flesh to skin during berry ripening. At the end of growing season, Ca content of rachis is almost 6 times greater than Ca content of berry in all treatments. Calcium accumulated mostly in the rachis and less in the flesh during grape berry development. Yield components including berry weight, cluster weight, and thus total yield per vine were not significantly influenced by Ca sprays, whereas berry drops and botrytis infection were reduced by Ca sprays. Quality components including juice-pH, SSC, and titratable acidity were not significantly affected, whereas berry firmness, berry color, and appearance improved at harvest time. A Ca-K antagonism was observed in this investigation. The vines in the high-Ca concentration (T4) treatment sometimes exhibited leaf injury (lesions), but this was not observed on cluster and berries.