Effect of gibberellin treatment on parthenocarpic ability and promotion of fruit swelling in papaya

Abstract: To improve the productivity of vegetable papaya in subtropical regions, 1) fruit setting rate (parthenocarpic ability) and fruit productivity between sex types (females and hermaphrodites) and among cultivars; and 2) effect of gibberellins (GAs) on fruit swelling, was studied. In both sex types, the number of fruits per tree correlated more closely with fruit yield than with individual fruit weight. Females produced higher number of fruits per tree, thus attaining a higher fruit yield than hermaphrodites. A variation in parthenocarpic ability was observed among cultivars, and this ability was higher in female plants than in hermaphrodites. These results suggest that it is possible to grow female cultivars with high parthenocarpic ability. However, parthenocarpic fruits were significantly smaller than those produced by pollination. GA treatment was found to be effective for promoting fruit swelling under greenhouse conditions. Thus, in the greenhouse production of papaya, GA treatment was more efficient than hand pollination. Based on these results, we suggest that in subtropical regions, efficient production of papaya fruit for use as a vegetable may be realized by selection and cultivation of female cultivars with high parthenocarpic ability and promotion of fruit swelling by GA treatment.