Effects of GA3 growth regulator on preventing young fruit abscission and improving seed quality of Ngoc Linh Ginseng

Ngoc Linh ginseng (Panax vietnamensis Ha et Grushv.) is a valuable endemic medicinal plant of Vietnam. However, premature fruit abscission and low seed quality have limited the production of high-quality seedlings for large-scale cultivation. This study aimed to evaluate the effects of gibberellic acid (GA3) on young fruit retention, seed quality, seedling establishment and the growth performance of Ngoc Linh ginseng seedlings. The experiment was conducted from March 2022 to March 2024 at the Ngoc Linh Ginseng and Medicinal Plant Development Center, Quang Nam Province, Vietnam. Four treatments were arranged in a randomized complete block design with three replications, including water spray (control), GA3 at 30 ppm, 60 ppm, and 90 ppm. The results showed that GA3 application had no effect on flower color but significantly improved several reproductive and seedling characteristics compared with the control. Application of GA3 at 60 ppm produced the highest number of flowers per inflorescence (61.30 flowers), flower diameter (3.65 mm) and peduncle length (1.48 cm). The same treatment also resulted in the highest germination percentage (82.48%), seedling establishment rate (79.71%) and nursery survival rate (76.88%). Furthermore, seedlings treated with GA3 at 60 ppm exhibited superior growth, with plant height, canopy diameter, stem diameter and fresh weight of 100 tubers reaching 15.65 cm, 10.62 cm, 1.95 mm and 133.84 g, respectively. These findings indicate that foliar application of GA3 at 60 ppm is an effective approach to reducing premature fruit drop, improving seed quality and enhancing seedling growth of Ngoc Linh ginseng, thereby contributing to the production of high-quality planting materials for sustainable cultivation.