Role of gibberellins in parthenocarpic fruit development induced by the genetic system pat-3/pat-4 in tomato

The role of gibberellins (GAs) in the induction of parthenocarpic fruit-set and growth by the pat-3/pat-4 genetic system in tomato (Lycopersicon escul entum Mill.) was investigated using wild type (WT; Cuarenteno) and a near-i sogenic line derived from the German line RP75/59 (the source of pat-3/pat- 4 parthenocarpy). Unpollinated WT ovaries degenerated but GA(3) application induced parthenocarpic fruit growth. On the contrary, parthenocarpic growt h of pat-3/pat-4 fruits, which occurs in the absence of pollination and hor mone treatment, was not affected by applied GA(3). Unpollinated pat-3/pat-4 fruit growth was negated by paclobutrazol, an inhibitor of ent-kaurene oxi dase, and this inhibitory effect was negated by GA(3). The quantification o f the main GAs of the early 13-hydroxylation pathway (GA(1), GA(8), GA(19), GA(20), GA(29) and GA(44)) in unpollinated ovaries at 3 developmental stag es (flower bud, FB; pre-anthesis, PR; and anthesis, AN), by gas chromatogra phy-selected ion monitoring, showed that the concentration of most of them was higher in pat-3/pat-4 than in WT ovaries at PR and AN stages. The conce ntration of GA(1), suggested previously to be the active GA in tomate, was 2-4 times higher. Unpollinated pat-3/pat-4 ovaries at FB, PR and AN stages also contained relatively high amounts (5-12 ng g(-1)) of GA(3), a GA found at less than 0.5 ng g(-1) in WT ovaries, It is concluded that the mutation s pat-3/pat-4 may induce natural facultative parthenocarpy capacity in toma to by increasing the concentration of GA(1) and GA(3) in the ovaries before pollination.