Ethephon-Induced Abscission of Oil Palm Fruits at Optimal Bunch Ripeness and Retting Period to Improve Commercial Seed Production

Abstract

Oil palm seed producers typically require 10 months of various processes from pollination to seed germination to produce commercial dura × pisifera hybrid seeds. Conventional forced fruit shedding from underripe fresh fruit bunches (FFB) usually causes seed damage and an extended retting period (incubation for natural fruit abscission from spikelets), eventually leading to bunch rot and disease infection. As a fruit ripening agent, ethephon has been explored to hasten fruit abscission in many fruit crops and oil palm. Nevertheless, the previous studies in oil palm only focused on fruit shedding from FFB to improve oil extraction rate in oil mills without considering the actual FFB ripeness and retting period, which are critical for oil palm seed production. In this study, the application of ethephon containing buffer (adjusted to pH 9.0) to underripe FFB at 145 days after pollination (DAP), 135 DAP and 125 DAP resulted in 50% more fruit abscission after a 72-h incubation. Considering the minimal seed loss upon FFB harvest (<1%) and 50% reduction in retting period, underripe FFB at around 145 DAP was found to be optimum for seed production using ethephon treatment. The treatment, however, made negligible improvement in fruit detachment for ripe FFB at 150 DAP and older. Importantly, seed germination and culling rate at nursery stages were not significantly affected by the ethephon treatment. Hence, ethephon application can improve commercial seed production practices for oil palm.