Influence of some plant growth regulators on fruit set, yield and quality of sugar apple (Annona squamosa L.) var. Arka Neelachal Vikram

Aim: To evaluate the efficacy of foliar application of homobrassinolide (HBL), gibberellic acid (GA3), and naphthalene acetic acid (NAA) for improving fruit set, yield, and quality in sugar apple. Methodology: The experiment was laid out in a randomized block design with 10 treatments, comprised of NAA (50,100, and 150 ppm), HBL (0.1,0.3, and 0.5 ppm), GA3 (100,150, and 200 ppm), and water as a control. Treatments were foliar sprayed thrice during major flowering period at monthly interval, i.e., April, May, and June. Observations were recorded on fruiting, yield, and fruit quality parameters. Results: Foliar application of GA3 at 150-200 ppm was found effective for enhancing the fruit set, fruit retention, and yield in sugar apple, when applied during May and June. Application of GA3 @ 200 ppm not only recorded the maximum fruit set and retention in May (5.03 and 69.18 %) and June flowering (9.38 and 75.35 %), but also scored the maximum values for number of fruits, fruit weight, and yield in their corresponding month of harvesting, i.e., October (50.60 fruits per tree, 235.70 g per fruit, and 11.88 kg per tree) and November (36.79 fruits per tree, 231.88 g per fruit, and 8.40 kg per tree). With respect to fruit quality, GA3 (100-200 ppm) and NAA (100-150 ppm) registered a significant improvement in various fruit quality parameters, however, GA3 treatments excelled in the performance. Fruits harvested from 200 ppm GA3 had the best quality (pulp: 72.07 %, TSS: 23.90 °B, TSS/acid ratio: 59.81, total sugar: 30.37 %, reducing sugar: 19.57 %, nonreducing sugar: 10.80 %, vitamin C: 52.34 mg 100 g"1 pulp, total flavonoid: 44.21 mg QE 100 g"1 FW, ferric reducing antioxidant power: 40.73 mM Fe(ll) 100 g"1 FW and scavenging activity: 74.65 %), followed by 150 ppm GA3. Interpretation: In sugar apple, foliar application of GA3 (150-200 ppm) twice during May and June flowering is effective for improving fruit set and enhancing yield and quality of the produce.