RESPONSES OF APPLES TO POSTHARVEST JASMONATE TREATMENTS

The effect of exogenous methyl jasmonate (MJ) and jasmonic acid (JA) c ompared with the effect of ethephon on surface color and quality of 'G olden Delicious' and 'Fuji' apples (Malus x domestica Borkh.) was stud ied. Treatments were applied by dipping fruit in water solutions of JA , MJ, or ethephon or by exposing fruit to MJ vapors. Response to MJ va por treatment depended on fruit developmental stage, with the maximum effect occurring as fruit began to produce ethylene. MJ promoted color changes more effectively than JA. The promotive effect of JA increase d with JA concentration. A minimum concentration of 0.1 mmol.L-1 JA wa s needed to promote significant color change within 15 d at 20 degrees C. JA at 1 or 10 mmol.L-1 promoted color change more effectively than 0.35 or 3.5 mmol.L-1 ethephon. The magnitude of JA-promoted responses decreased at lower temperatures. Treatments with 10 mmol.L-1 JA or 3. 5 mmol.L-1 ethephon were phytotoxic. Treatments using JA at 1 or 10 mm ol.L-1 in water promoted loss of fruit titratable acidity compared to controls. Firmness and soluble solids content were relatively unrespon sive to JA treatments. Based on these results, using JA and MJ to prom ote degreening of apple fruit with minimal loss of other quality attri butes appears feasible.