Exogenous anti-gibberellin agents for biennial bearing management in Balady mandarin trees
Pomology Department, Faculty of Agriculture, Cairo University, Egypt. Corresponding e-mail:ahmed.rasheedy@agr.cu.edu.eg
DOI: https://doi.org/10.37855/jah.2025.v27i04.131
Full text PDF Exogenous application of growth regulators often induces physiological changes by altering endogenous hormone levels, thereby affecting plant productivity. Consequently, this trial aimed to explore the impacts of anti-gibberellin (A-GA) agents, using both abscisic acid (ABA) and ethephon (ETH) at 50 ppm alongside a control, before the Off-year season (at flower bud induction period) twice during the last week of December and January on fruit yield, cumulative impacts on the following On-year and biennial bearing (BB) of Balady mandarin trees. Regarding the two Off-years, ETH effectively decreased endogenous GA content in March by 28.26% and 29.78%, while it increased the C/N ratio by 16.67% and 14.29%, the number of fruits by 55.18% and 50.26%, and fruit yield by 50% and 45.45%. Also, ABA decreased endogenous GA content in March by 8.46% and 16.10%, while it increased the number of fruits by 87.4% and 52.8% and increased fruit yield by 75% and 45.45%. ABA increased Off-year yield by 12.48% relative to ETH. Concerning the following two On-years, higher endogenous GA content was observed in the previous September (Off year) in A-GA treatments, resulting in a decrease in mandarin fruit yield. ETH decreased the number of fruits by 17.37% and 24.1%, resulting in increases of 3.8% and 16% in fruit weight. Also, ABA decreased the number of fruits by 22.94% and 6.97%, resulting in increases of 10.34% and 10.71% in fruit weight. Furthermore, ETH decreased BB by 39% and 60% and ABA decreased BB by 52.44% and 38.24%. Using A-GA agents prior to the off year during the flower bud induction period alleviates BB in Balady mandarin trees.
