STUDIES ON FLOWERING, FRUITING AND RESIDUAL EFFECT OF SOME BREAKING DORMANCY AGENTS ON TWO PLUM CULTIVARS

Abstract

this study was conducted during 2014 and 2015 seasons to compare the effect of spraying dormancy-breaking agents Dinitro-O-Cresol (DNOC) in the form of Universal oil at two concentrations (5% and at 6%); Duromix (which contains 50 % Hydrogen cyanamide) at 1% + Mineral oil at 1.5 %; Thiourea at 1.5% + Mineral oil at 1.5 %; Light mineral oil at 2% [CAPL2] and control treatment, at mid-January, in two seasons, on flowering; fruiting and detecting the residual effect of breaking agents on Hollywood and Beauty plum cultivars. Measurements included chilling requirements; dates of different stages of flower bud opening; flower bud opening percentages; fruit set percentages; heat requirements; dates of fruit maturity; yield; fruits physical and chemical properties and the residual of breaking agents in fruits. Results indicated that calculating chilling hours using temperature at 10.0 0C or below was more suitable than the temperature at or below 7.2 0C or 15.0 0C. Application of all dormancy breaking agents had advanced fruit set stage which ranged from 17 to 21 days for the two cultivars. Universal oil at 6% and Duromix at 1% + Mineral oil at 1.5 % treatments gave the highest fruit set percentages of the two cultivars. Meanwhile, Universal at 5% and Duromix at 1% + Mineral oil at 1.5 % treatments gave the highest percentages of fruit set of Beauty cultivar. Universal at 6% had the lowest accumulated growing degree days from time of flower bud break till fruit maturity in Hollywood cultivar. Universal at 6% had the highest yield weight per tree in Hollywood and Beauty cultivars. Universal at 5%; Universal at 6% and Duromix at 1% + Mineral oil at 1.5 % had the earliest fruit maturation of the two cultivars. Universal at 6% and Duromix at 1% + Mineral oil at 1.5 % treatments significantly increased fruit size; weight and diameter of the two cultivars. There were no agent residues found in fruits in the two cultivars 110 days from after application. It can be recommended that Dinitro-O-Cresol at 6 % and Duromix at 1% + Mineral oil at 1.5 % were the best dormancy-breaking agents application on Hollywood and Beauty cultivars. Moreover, it is safely compounds to use