Degreening and Reducing Berry Shatter of Thompson Seedless Grapes by Using Safe Agricultural Chemicals

Berry color is one of the main fruit attributes that affect the marketability of Thompson seedless grapes. Yellowish berries are more desired by consumers especially at the beginning of the season. Consumers in many European countries have been demanding yellowish berries of “Thompson” seedless grapes. Ethrel was found to enhance the breakdown of chlorophylls and the formation of carotenes. However, Ethrel spray on Thompson grapes caused berry pinkishnes, loss of acidity and increased berry shatter. In this study, some safe chemicals, that have been already used in agriculture, were sprayed to increase yellowish-colored berries. Treatments included EDTA alone or bound with either Cu, Zn, K in addition to diluted sulphuric acid, copper sulphate, potassium sulphate, zinc sulphate and the control (water spray). All treatments were applied to the run off at a concentration 0.05% (w/v). The non-ionic surfactant Tergitol (at 0.1%, v/v) was added to all treatments. Bunches were harvested ten days after spray for the determination of some physical and chemical characteristics. Another group of bunches were exposed to precooling then stored at 1.0 ° C for 55 days for the assessment of berry shatter. The data revealed that various treatments did not significantly affect fruit weight or length while some reduced juice volume such as zinc sulphate, Zn EDTA, potassium sulphate, K EDTA and diluted sulphuric acid when compared with the control. Berry shatter after cold storage was not, generally, affected except with Cu EDTA that caused an increase in such shatter as compared J.Agric.&Env.Sci.Alex.Univ.,Egypt Vol.5 (2)2006 14 with the control especially in the first season. Total soluble solids in the berries increased significantly by some treatments such as zinc sulphate, Zn EDTA and diluted sulphuric acid in both seasons. Furthermore, Zn EDTA caused a significant increase in carotenes in the berry skin without a significant change in chlorophylls a and b in both seasons. The present study provided evidence about the possibility of utilizing some already used agricultural chemicals for other purposes such as accelerating yellowish color formation of grape berries by Zn EDTA.