Effects of Prohexadione- calcium and some Oranic Compounds on Fruit Thining and Quality of Allple cv. Red Delicious in Semirom Areas

In order to study the effects of mineral and biological compounds as thinning agents on fruit quantitative and qualitative characteristics of apple cv. Red Delicious and to compare them with flower and fruit-hand thinning, a research was carried out in a commercial orchard in Semirom, Iran. Treatments included lime-sulfur (6%, 8% and double application of 6% first at 30-40 and then 70-80 bolting percentage), ammonium thiosulfate (20, 25 and twice application of 20 mll-1 (in 30-40 and 70-80 bolting percentage) and prohexadione- calcium, Apogee® (300, 450 and twice application of 300 mgl-1 (first at 70-80 bolting percentage and then 2-3 weeks after FB), and hand-thinning of flowers (at full bloom) and fruits (at 4 week after FB),which were applied on selected trees. The results showed that all of the treatments except Apogee (300 and 450 mgl-1) significantly thinned the fruits and reduced fruit set (10 -50 %). The treatments increased fruit weight(51%), volume(48%), total soluble solids (23%), TSS/total acid ratio(38%) and color and enhanced leaf area index (30%). There were no significant difference between control and the total acidity of fruits. Twice application of 20 ml ammonium thiosulfate was the best economically treatment. In terms of yield and yield efficiency(TCSA), treatments were significantly different, so that the control and lime sulfur 8% had the highest and lowest yield, respectively.