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 esculentum Mill.) was investigated using wild type (WT; Cuarenteno) and a near‐isogenic line derived from the German line RP75/59 (the source of pat‐3/pat‐4 parthenocarpy). Unpollinated WT ovaries degenerated but GA3 application induced parthenocarpic fruit growth. On the contrary, parthenocarpic growth of pat‐3/pat‐4 fruits, which occurs in the absence of pollination and hormone treatment, was not affected by applied GA3. Unpollinated pat‐3/pat‐4 fruit growth was negated by paclobutrazol, an inhibitor of ent‐kaurene oxidase, and this inhibitory effect was negated by GA3. The quantification of the main GAs of the early 13‐hydroxylation pathway (GA1, GA8, GA19, GA20, GA29 and GA44) in unpollinated ovaries at 3 developmental stages (flower bud, FB; pre‐anthesis, PR; and anthesis, AN), by gas chromatography‐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 concentration of GA1, 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 GA3, a GA found at less than 0.5 ng g−1 in WT ovaries. It is concluded that the mutations pat‐3/pat‐4 may induce natural facultative parthenocarpy capacity in tomato by increasing the concentration of GA1 and GA3 in the ovaries before pollination.