Effect of Fruitlet Thinning on Apple Production and Quality under High Density Plantation

Abstract

This study, conducted within the Experimental Block of the Division of Fruit Science at SKUAST-K, Shalimar, India, was aimed to thin 5-year-old Fuji Zehn Aztec apple plants. The research was carried out during the years 2020 and 2021and implemented a Randomized Complete Block Design with 11 treatments, including control and various other thinning methods. Chemical and hand thinning were practised at the 12 mm king fruitlet diameter stage. Among the treatments, T9 (NAA+BA@15+140ppm) demonstrated significant results, with the highest trunk girth increment (0.41 cm), annual shoot extension growth (65.46 cm), leaf area (34.71 cm2), fruit drop (39.26%), and the least reduction in return bloom (52.22%). Additionally, T9 resulted in maximum fruit length (79.98 mm), fruit diameter (89.00 mm), fruit weight (224.90 g), fruit volume (197.86 cm3), Soluble Solid concentration (15.87%), SSC : acidity (40.08), total sugar content (11.07%), anthocyanin content (7.14 mg/100g), ascorbic acid content (6.94 mg/100g), and received the highest organoleptic rating score (4.87). However, the highest yield (21.97 kg/tree), yield efficiency (1.50 kg/cm2), fruit firmness (8.36 kg/cm2), hue angle (68.57°), and acidity (0.59%) were recorded in the control group. Notably, T1 (Hand thinning @ 2 fruitlets retained per cluster) achieved the highest fruit retention (97.97%) and the maximum leaf-to-fruit ratio (27.50). These findings shed light on the potential benefits and trade-offs associated with different fruitlet thinning methods in high-density apple plantations. Understanding these effects can aid orchard management practices to optimize both production and fruit quality.