Effect of Exogenous Application of Gibberellic Acid (GA3) on Seed Size and Fruit Quality of Prickly Pear Cactus (Opuntia ficus-indica)

Abstract

The present work includes studying the effect of different concentrations of gibberellic acid (GA3, 100, 300, and 500 ppm) on seed and quality fruit development in the prickly pear cactus plant. Seeds are known to be essential for normal growth of fruits. Indeed, the fruit size and shape are determined by the seed number and distribution. The fruits may contain both normal and aborted seeds, and in some cases, aborted ones may be able to partially contribute to the pulp tissue regeneration. For achieving the purpose of reducing the seed size and improving the fruit quality, treatments comprising GA3 spray were applied on the floral bud between 5:30 and 8:30 a.m. at different stages [stage 1: buds were 1 to 1.5 cm in diameter (3 days from anthesis); stage 2: buds were 1.5 to 2.0 cm in diameter and slightly rounded at the apex (7 days from anthesis); stage 3: buds were of similar diameter as stage 2 but more rounded at the apex due to internal development of floral parts (9 days from anthesis)] and twice subsequently at intervals of 21 days. Different GA3 concentrations were tested for their ability to produce well-formed and seedless fruits. Spray with different concentrations of GA3 (0, 100, 300, and 500 ppm) was applied on the research farm at the Sohag University in southern Egypt. GA3 application allowed ovules of all treated flowers to give partially developed seeds that were able to ensure sufficient support for fruit development. In this way, emasculation is not necessary to produce GA3-mediated parthenocarpic cactus fruits. The results indicated that spraying 500 ppm of GA3 on floral buds was the most effective way to reduce the number of seeds in prickly pear fruits; however, it led to producing less marketable fruits compared to spraying with a concentration of 100 ppm. This fruit is closest in size to the untreated fruit and has the greatest market value.