Effects of Paclobutrazol and Environmental Factors on Early Flowering, fruit Setting and Quality of Durian

Abstract

Experiment on paclobutrazol (Cultar) to induce early flowering was conducted in 12-years-old durian cv. chanee (Durio zibethinus Murr.) After harvest, selected trees were pruned, followed by management to stimulate leaf flushing. Paclobutrazol, at the rates of 0, 750, 1000 and 1500 ppm, were sprayed to durian trees when the new flushing leaves developed to the stage of fully expanded.
flowering in treatd trees occurred 14 to 45 days earlier than that of the untreated trees Flowering response to paclobutrazol, was more readily in higher rates. In general, as climatic conditions prevailed, a prerequisite of 10 to 14 days of continuous dry period was required for untreated trees to induce flowering. In contrast, an interuption of 3 to 7 days of continuous dry period after chemical treatment was sufficient to promote flowering in treated trees. When compared with the untreated or control trees, the number of flowers per tree in trees treated with paclobutrazol was increased by 29 to 64%. It had been also observed that fruit set and fruit development were not influenced by paclobutrazol application, however, the rates of flower and fruit development were delayed. Results of the experimont indicated that a successful induction of flowering by using paclobutrazol involved the degree of vegetative growth suppression, concentration and time of chemical application and an interrupt of continuous dry period.