Effect of bioregulators preharvest application on date palm fruit productivity, ripening and quality

This study was conducted during 2010 and 2011 to investigate the effect of preharvest sprays on yield, harvest date, harvest period and fruit physico-chemical quality characteristics at commercial harvest date of Sokary date palm growing in Riyadh area, Saudi Arabia. These palms were sprayed at hababouk and khalal stages with naphthalene acetic acid (NAA), gibberellic acid (GA3), cytofex (CPPU), putrescine (Put), salicylic acid (SA) or ethyphon (Eth). The results showed that the yield components and fruit physical characteristics (except ground color) were improved by all sprayed bioregulators, especially NAA, GA3 and CPPU. The applications of bioregulators delayed harvest date in comparison with the control and Eth treatments. The latest harvest date was obtained with NAA followed by GA3 and CPPU treatments. On the other hand, Eth advanced fruit ripening date in comparison with the control. All the bioregulator treatments decreased the harvest period and the percentage of unmarketable fruits. It also delayed fruit carotenoids pigment formation, but increased fruit acidity and chlorophyll content as compared with control and Eth treatments. Fruit TSS and sugar content at rutab stage were higher compared to the control. However, at tamar stage, fruit acidity was decreased by all treatments.   Key words: Date palm, bioregulators, preharvest, yield, ripening fruit quality.