Role of growth regulators on fruit splitting and nutritional status of Daisy Mandarin in subtropical conditions
摘要
Daisy mandarin is a commercially important cultivar of citrus, well known for its superior fruit quality and adaptability to subtropical climates. However, the fruit splitting and imbalances in leaf nutrient content often limits its productivity. To address this issue, a field experiment was carried out during 2021 and 2022 at the Fruit Research Station, Jallowal-Lesriwal, Jalandhar, to evaluate the influence of different growth regulators on the incidence of fruit splitting and leaf nutrient composition of Daisy mandarin budded on two rootstocks viz., Rough lemon and Carrizo Citrange. Maintaining the optimal foliar nutrient status is essential, as it plays a vital role in sustaining tree vigor, development of fruits and overall yield. This study involved the foliar application of gibberellic acid (GA3) at 10, 20 and 30 ppm, naphthalene acetic acid (NAA) at 10, 20 and 30 ppm; ethephon at 10, 20 and 30 ppm; and salicylic acid (SA) at 100 and 200 ppm concentration, applied at different phenological stages. The trial was conducted on Daisy mandarin trees budded on two different rootstocks i.e. Rough lemon and Carrizo citrange. Fruit splitting was observed to be more pronounced in Carrizo citrange rootstock than in Rough lemon, which may be attributed to higher soluble solids accumulation, weaker anatomical structure, and greater stress susceptibility. The pooled analysis over two consecutive years revealed that foliar application of SA at 100 ppm significantly reduced the fruit splitting incidence (3.14% and 3.60%) and enhanced the concentrations of nitrogen (2.65% and 2.66%), phosphorous (0.15% and 0.16%), potassium (1.65%), calcium (3.58% and 3.52%), magnesium (0.35%), and other micro nutrient content of Daisy mandarin in the leaves followed by other growth regulators as compared to other untreated (control) plants. These results suggest that SA at 100 ppm is a promising foliar treatment for improving the nutritional status of Daisy mandarin in the subtropical conditions of Punjab.