Pre-harvest fruit drop, bunch weight and fruit quality of ‘Rothana’ and ‘Ghur’ date palm cultivars as affected by some plant growth regulators

Abstract

Pre-harvest fruit drop is a serious problem of some date palm cultivars. During 2010 and 2011 seasons, the effect of plant growth regulators 2,4-dichlorophenoxyacetic acid (2,4-D) (50 and 100 ppm), naphthalene acetic acid (NAA) (100 and 150 ppm), gibberellic acid (GA₃) (100 and 150 ppm) and benzyladenine (BA) (100 and 150 ppm) applications, at 40 and 70 days after pollination, on pre-harvest fruit drop and quality of ‘Rothana’ and ‘Ghur’ dates were studied. In both cultivars, the application of growth regulators at both rates significantly decreased fruit drop. In this respect, 2,4-D and GA₃ were the most effective treatments followed by BA, while NAA was the least effective. The reduction in fruit drop resulted in a higher bunch weight in the treated fruit than the control. The high rate of BA was more effective than the low rate in decreasing fruit drop of ‘Ghur’ cultivar. In ‘Rothana’ cultivar, bunch weight was higher than the control with both 2,4-D rates; whereas, with GA₃ and BA, only the high rate was effective; while in ‘Ghur’ cultivar, bunch weight of all growth regulators treatments was higher than the control. The rutab percentage was lower in NAA treatments than for all the other treatments, except for control in ‘Ghur’ cultivar. Fruit and flesh weight of ‘Rothana’ cultivar were higher at the high rate of 2,4-D, the low rate of GA₃ and BA treatments than in the control. There were no consistent effects for growth regulators on the physical and chemical quality characteristics of fruit, possibly due to the large variations of the fruit load among the treatments. It was concluded that under hot arid conditions, the application of growth regulators of especially 2,4-D (50 ppm) and GA₃ (150 ppm) at both 40 and 70 days from pollination is recommended to reduce pre-harvest drop, and improve fruit quality of both ‘Rothana’ and ‘Ghur’ date palm cultivars.

Keywords: Date palm, plant growth regulators, yield, quality, fruit drop, Phoenix dactylifera L