Effect of Putrescine, Gibberellic Acid and Calcium on Quality Characteristics and Maturity Delay of "desert Red" Peach Fruit Cultivar

This study was conducted during two successive seasons 2005 and 2006 by using "Desert Red" peach cultivar (Prunus persica L.) grafted on Nemaguard rootstock. Trees were sprayed with a hand sprayer to the run off at the initiation of phase ΙΙΙ of the double sigmoid curve before the onset of the climacteric. The treatments included putrescine at 5 and 10 mM, GA3 at 200 and 400 ppm, in addition to each of the above treatments plus calcium chloride (at 2%, w/v), CaCl2 alone, and the control (water spray). The surfactant tween-80 was added to all treatments at 0.05% (v/v). Skin of putrescine-treated fruits contained higher amount of chlorophyll a than the control. In a similar manner, both GA3 concentrations resulted in higher content of chlorophyll a especially in the first season. Moreover, CaCl2 treatment did not cause a significant change in chlorophyll a in both seasons. Putrescine at 5 or 10 mM, and CaCl2 did not result in a significant change in carotene content, while GA3 at 200 ppm caused a reduction in carotenes as compared with the control. Various used putrescine and GA3 concentrations caused a significant reduction in anthocyanin content as compared with the control in both seasons. Similarly, CaCl2 alone was able to significantly reduce anthocyanin content in fruit skin while its addition to any of putrescine or GA3 treatments did not, J.Agric.&Env.Sci.Alex.Univ.,Egypt Vol.6 (1)2007 58 generally, caused a significant alteration in anthocyanin content. Putrescine at 10 mM consistently reduced TSS/ acidity ratio as compared with the control. While, GA3 in general, tended to reduce such ratio when compared with the control. Meanwhile, CaCl2 did not result in a significant change in TSS to acidity ratio in both seasons. Combing CaCl2 with each of putrescine or GA3 concentrations did not result in added advantage in terms of inducing further reduction of deteriming pigments or sugars. This study recommended spraying GA3 at 200 ppm or putrescine at 10 mM (882ppm) or calcium chloride at [2% (w/v), 20,000 ppm] to delay “Desert Red” peach fruit maturity by, at least one week provided that treatments must be applied at the beginning of the third phase of the double sigmoid curve.