Effect of pre-harvest methyl jasmonate treatments on ethylene production, water-soluble phenolic compounds and fruit quality of Japanese plums.

Background: The effects of pre-harvest methyl jasmonate (MJ) treatments on ethylene production, respiration rate, bioactive compounds and physico-chemical parameters of plum fruits (Prunus salicina Lindell cv. 'Fortune' and 'Friar') were investigated. Whole trees were sprayed once with an aqueous solution containing MJ (0, 1120 and 2240 mg L(-1)) 2 weeks before the anticipated commercial harvest for each cultivar.

Results: In both plum cultivars, 1120 mg L(-1) MJ significantly increased hue angle of fruits. The fruit mass and geometric mean diameter were lower in MJ treatments while flesh firmness was higher, except at initial harvest date. Soluble solids concentration increased and titratable acidity decreased with MJ treatments. MJ-treated fruits exhibited higher levels of ethylene production and respiration rate. MJ was more effective in increasing water-soluble antioxidant activity, water-soluble phenolics and individual phenolics. Chlorogenic acid, caffeic acid, rutin, ferulic acid, naringenin and kaempferol contents significantly increased with 2240 mg L(-1) MJ.

Conclusions: This study revealed that pre-harvest MJ treatments were effective in delaying softening of late-harvested fruits and increasing bioactive compounds of plum fruits.