Gibberellic Acid Spray Modulates Fruiting, Yield, Quality, and Shelf Life of Rambutan (Nephelium lappaceum L.)

A lucrative and delicious nonclimacteric tropical fruit, rambutan, has disadvantages of inadequate fruiting, low yield, and inferior edibility at farm level that need to be addressed. Moreover, unstable tropical temperatures and humidity threaten poor fruit set and insufficient rambutan yields. Therefore, the study revealed the effectiveness of gibberellic acid (GA3) on fruit set and retention, fruit size and yield, shelf life, and postharvest properties of rambutan under these atmospheric conditions. GA3 at concentrations of 50, 100, 200, 300, 400, and 500 ppm, apart from the control (without GA3), was applied to panicles twice in the early flowering and the early fruiting stages (thirty days after the first spraying). The results showed that maximum fruit set (223.2 per panicle), retention (13.2 per panicle, 5.9%), and yield (714.0 g per panicle) were obtained by GA3 treatment at 300 ppm. In addition to increasing fruit size (54.1 g) and pulp weight (31.3 g), GA3 at a dose of 300 ppm significantly reduced seed weight by 27.5% and increased the edible portion by 26.6% compared to the control. Notably, preharvest GA3 treatment increased TSS content (19.0%), total sugar (4.5%), and shelf life (11.5 days), while it decreased titratable acidity (0.4%) of rambutan. GA3 doses from 200 to 500 ppm had similar effects in terms of affecting the edible properties and shelf life of rambutan. However, fruit set, retention, and yield exhibited distinct dose-dependent responses, with 300 ppm being the best and 200 ppm consistent with the best, with some differences. Regression analysis showed a skewed curve explaining higher yield and better fruit quality at the medium GA3 treatment level (250–350 ppm). In comparison, lower (< 200 ppm) and higher (> 400 ppm) doses resulted in worse results in most cases. Therefore, regulated use of GA3 is necessary to improve rambutan yield and fruit quality.