Changes of jasmonates in grape berries and their possible roles in fruit development

Jasmonates [jasmonic acid (JA) and methyl jasmonate (MeJA)] were quantified in the skin of seeded and seedless 'Pione' grapes (Vitis spp.) treated with gibberellic acid (GA(3)). In both types of fruit, JA concentrations were higher than those of MeJA. JA and MeJA concentrations in seeded berries were high in the early growth stage of fruit development and decreased with days after full bloom (DAFB). JA concentration in seedless berries reached a peak at 53 DAFB and then decreased. MeJA in seedless berries remained unchanged from 20 DAFB to 83 DAFB (harvest). Fruit firmness in the seeded berries decreased after 53 DAFB and after 41 DAFB in the seedless berries. The timing of firmness showed an inverse relationship with levels of anthocyanin. These results demonstrate that these dates may mark the veraison stage. Changes of JA and MeJA in the skin of both types of fruits were not recognized in this period. Therefore, a direct correlation between maturation, softening and coloring, and jasmonates in the skin was not observed. JA concentration in the seed increased toward harvest. The possible effect of jasmonates on the dormancy of the seed was discussed. The function of JA in callus formation was examined on discs taken from pulp sampled at 18 and 28 DAFB and cultured on B5 medium including combinations of NAA, BA, and JA. Generally, callus weight gain was induced more at 18 DAFB than at 28 DAFB. The callus formation in the medium with NAA plus BA combination at both sampling dates was induced by 0.45 mu mol JA. This result demonstrates that endogenous JA may stimulate cell division in grape berries. The interactions between jasmonates and abscisic acid (ABA) were also investigated. Discs from pulp at 50 DAFB were sampled and placed in petri dishes including 0.4 mol mannitol solution with MeJA or ABA. Jasmonates and ABA in pulp discs were measured at 0, 24, 48, and 72 h after the initiation of treatment. With few exceptions, MeJA and ABA treatments did not influence the mutual endogenous concentrations. (C) 2001 Elsevier Science B.V. All rights reserved.