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

Abstract:

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 exculentum Mill.) was investigated using wild type (WT; Cuarenteno) and a nearisogenic line derived from the German line RP75/59 (the source of pat-3/pat-4 parthenocarpy). Unpollinated WT ovaries degenerated but GA<inf>3</inf> 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 GA<inf>3</inf>. Unpollinated pat-3/pat-4 fruit growth was negated by paclobutrazol, an inhibitor of ent-kaurene oxidase, and this inhibitory effect was negated by GA<inf>3</inf>. The quantification of the main GAs of the early 13-hydroxylation pathway (GA<inf>1</inf>, GA<inf>8</inf>, GA<inf>19</inf>, GA<inf>20</inf>, GA<inf>29</inf> and GA<inf>44</inf>) 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 GA<inf>1</inf>, 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<sup>-1</sup>) of GA<inf>3</inf>, a GA found at less than 0.5 ng g<sup>-1</sup> 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 GA<inf>1</inf> and GA<inf>3</inf> in the ovaries before pollination.