Exogenous Chemical Application to Regulate Sex Expression in Gynoecious Bitter Gound

Abstract

Globally, bitter gourd (Momordica charantia L.) cultivation largely depends on F1 hybrid seeds to ensure high yield and uniformity. The gynoecious sex form, which produces only female flowers, plays a vital role in hybrid seed production; however, its commercial application is constrained by the lack of cost-effective methods for maintaining gynoecious lines, as self-pollination is not possible. Bitter gourd is a monoecious vine exhibiting a protandrous flowering pattem, where male flowers appear earlier than female flowers, leading to an imbalanced sex ratio and low productivity. Developing gynoecious varieties is considered the most effective strategy to increase yield, but seed production in these lines poses a significant challenge. Sex expression in bitter gourd is influenced by genetic and environmental factors, including nutrient levels and phytohormones such as ethylene and gibberellic acid (GA3). While ethylene promotes femaleness, GA3 favors maleness. Silver nitrate (AgNO3 ), an ethylene inhibitor, has been used to manipulate sex expression. This study evaluated the effects of AgNO3 and GA3 on the induction of hermaphrodite and female flowers in gynoecious bitter gourd. The experiment was conducted in a poll.tunnel at Onesh Agri (Pvt) Ltd, Giriulla, Sri Lanka, using the gynoecious line BG 043. Eleven treatments, including combinations of AgNO3 and GA3, were tested under a Completely Randomized Design (CRD) with three replications. Reproductive traits were monitored throughout flowering. Results revealed that AgNO:, especially at 600 ppm & 1200 ppm, was most effective in inducing hermaphrodite flowers with consistent flowering patterns, while GA3 promoted female flowers without sex reversion. The earliest appearance of hermaphrodite flowers occurred approximately 12 days after spraying. These findings confirm that silver nitrate can be effectively used for sex modification in breeding programs. Futwe studies should extend observations to seed development to assess the viability of hermaphrodite-induced flowers and evaluate the potential of adopting this technique in commercial hybrid breeding.