Effect of Application with Gibberellin GA4+7 on Russeting of „Golden Delicious” Apples

Abstract

Worldwide, the presence of russet on ‘Golden Delicious’ apples has been a concern to producers and marketers of fresh fruit for a long time due to the fact that it decresses the smoothness, perfomes an uniform finish of the fruit and results in economic loss thru quality reduction. Apple cultivars present different degrees of susceptibility to russeting, and fruits in early stages of development are more susceptible than those in later stages. Under orchard conditions, russeting is avoided. For sensitive cultivars the aspect of peel is improved by applying gibberellin GA 4+7. The study subject of the experience was ‘Golden Delicious’ apple variety grafted on M 9. The trees were trained as slender spindles. The distance of plantation is 3.5 x 1.2 m. The tested gibberellic acid was GA 4+7 , (Gerlagib LG). To study russeting of the apple fruits were experimented the following variants of treatment: 1. Control – no treatment; 2. GA 4+7 - 4 mg L -1 ; 3. GA 4+7 - 5 mg L -1 . Trees were sprayed 4 times. The experiment was conducted in the year 2013. During the research, we studied the amount and average of fruits, tree production, firmness of fruits, and  hydrolysis index. Russeting of fruit was estimated at harvest using a grading scale (S. J. Wertheim). It was established that, gibberellic acid GA 4+7 may be included in prevention system of apple fruits russeting with a,  dose of 5 mgL -1 , applied up to 4 times by treatment. First treatment should be performed starting at the beginning of petal fall stage, and the next 3 treatments 7-10 days after previous.