Progress in research on the control of peteca spot of lemon fruit: could ethylene metabolism influence susceptibility?

摘要

Peteca spot (PS) of lemon is a postharvest physiological disorder resulting in the collapse of the oil gland. Subsequently, the oil leaks into the adjacent tissue and causes a darkened depression. The occurrence can be severe, without any specific pre- or post-harvest practises to avoid or reduce the incidence. PS occurs in all citrus production areas of South Africa and is thought to be the result of the immature rind being subjected to postharvest stress associated with high CO_2 concentration in degreening, as well as the physical impact of the packing line and wax application. Over several seasons the incidence of PS was investigated to identify factors influencing the disorder. The first observation was the highly erratic incidence between seasons as well as within an orchard in a season, with the early fruit being most susceptible. In experiments to identify postharvest factors that influence the PS incidence, 3 ppm ethylene and 1% CO_2 were applied in a continuous flow-through system (20°Cfor 3 d). The C02 treatment resulted in significantly higher incidence compared to the other treatments. Following on from these results, postharvest application of Eth-ephon (2-Chloroethyl phosphoric acid) (200mg/L and 400 mg/L) and AVG (aminoeth-oxy-vinylglycine) (400 mg/L and 800 mg/L) applications to fruit resulted in a significant reduction in PS.