Timing and rates of application of NAA as blossom and fruitlet chemical thinner on apple cv. and #712;Braeburn and #712;

Abstract

Three concentrations of NAA (0, 10, 15 and 20 μl•l-1) were studied at three application timings (flower, fruit and the combination of each other) in order to evaluate the thinning effect and physico-chemical attributes of apple cv. 'Braeburn' fruits. NAA concentration was more significant factor than timing in terms of fruit production. The number and yield of fruits over 70 mm in diameter significantly increased in all application timings within all concentrations of thinner as compared to control. Thinning at 15 μl•l-1 in flower application appeared the best. The highest share of fruits over 70 mm was acquired using 20 μl•l-1 NAA in fruit application time. The untreated trees yielded highest total number of fruits with maximum total yield efficiency and total yield efficiency in terms of number of fruits. NAA at 15 μl•l-1 increased the yield efficiency in terms of number of fruits over 70 mm and yield efficiency in terms of yield of fruits over 70 mm in diameter. Significant differences were found regarding the effects of NAA concentration and combination of both timing and concentration while timing alone showed non-significant results for SSC, TA, SSC/TA and starch. NAA at 20 μl•l-1 resulted in highest fruit firmness, SSC and TA in fruit application time. The highest levels of SSC/TA and starch degradation level were recorded with NAA at 15 μl•l-1 sprayed in combination of flower and fruit applications. Comparatively, application of 10 μl•l-1 NAA at both flower and fruit application timing is recommended to achieve best results.