Suppressing green mold decay in grapefruit with postharvest jasmonate application

Jasmonic acid (JA) and methyl jasmonate (MJ), collectively referred to as j asmonates, are naturally occurring plant growth regulators involved in vari ous aspects of plant development and responses to biotic and abiotic stress es. Hn this study, we found that postharvest application of jasmonates redu ced decay caused by the green mold Penicillium digitatum (Pers,: Fr,) Sacc. after either natural or artificial inoculation of grapefruit (Citrus parad isi 'Marsh Seedless'). These treatments also effectively reduced chilling i njury incidence after cold storage. The most effective concentration of jas monates for reducing decay in cold-stored fruit or after artificial inocula tion of wounded fruit at 24 degrees C was 10 mu mol L-1. Higher and lower j asmonate concentrations were less effective at both temperatures. MJ at 10 mu mol L-1 also most effectively reduced the percentage of fruit displaying chilling injury symptoms after 6 weeks of storage at 2 degrees C and 4 add itional d at 20 degrees C, When tested in vitro, neither JA nor MJ had any direct antifungal effect on P digitatum spore germination or germ tube elon gation. Therefore, it is suggested that jasmonates probably reduced green m old decay in grapefruit indirectly by enhancing the natural resistance of t he fruit to P. digitatum at high and low temperatures.