Application of plant growth regulators in prevention of autumn flowering in pear

Developed pear buds maintain their paradormant state and do not sprout throughout the growing season. However, early defoliation caused by leaf diseases often leads to bud paradormancy release and sprouting, resulting in out-of-season flowering in autumn. This phenomenon reduces flowering and fruit yield in the following spring, which is a production problem that needs to be addressed urgently. Our previous studies have shown that early defoliation induces auxin efflux from buds, promoting bud paradormancy release. It also altered the transcript levels of a number of genes related to hormones, such as auxin, cytokinin (CTK), and gibberellin (GA). Hence, we investigated whether early defoliation-induced autumn flowering could be prevented by regulating the levels of various hormones. In this study, we used a high concentration of the auxin analog 1-naphthaleneacetic acid (NAA), the CTK synthesis inhibitor lovastatin, and the GA synthesis inhibitor uniconazole to treat buds after early defoliation. We found that all three treatments inhibited bud break. Among them, the inhibition effect of a high concentration of NAA (300 mg L^‑1 NAA) was the most significant, reaching more than 50%. The inhibition effect of lovastatin and uniconazole was lower than that of NAA, at about 30-50%. Therefore, a high concentration of NAA can be used in production to inhibit autumn flowering. It can also be combined with CTK- and GA-related plant growth regulators such as lovastatin and uniconazole to develop a combination of autumn flowering inhibitors or more effective prevention methods.