Effects of exogenous gibberellin on anatomical structure and chemical composition of banana pericarp and fruit rust control

【Objective】 To study effects of exogenous gibberellin(GA) on anatomical structure and chemical composition of banana pericarp and fruit rust control, and to provide theoretical reference for banana production and cultivation technological improvement and sustainable and virtuous development of banana industry.【Method】 Baodao banana with resistance to Fusarium wilt was used as experimental material. 100 mg/L GA₄₊₇ was sprayed on fruit surface of Baodao banana during combing period, and banana fruits sprayed with clean water was taken as the control(CK). Fruit rust occurrence was observed in the field. Differences in pericarp tissue structure, chemical content, related enzyme activities and fruit quality were analyzed by optical microscope, fluorescence microscope and physicochemical analysis.【Result】 Banana fruit rust occurred 60 d after budding, and the disease increased as fruit swelled, the fruit rust index of GA₄₊₇ treatment was 18.0%(absolute value) lower than that of CK. Fruit rust occurrence was closely related to pericarp tissue structure and cell wall lignification, and compared to CK, in GA₄₊₇ treatment, cuticle thickness significantly increased by 63.6%, epidermal cell size and width-length ratio increased by 79.69 μm² and 0.14, but cell wall thickness decreased by 28.4%; compared to CK, in GA₄₊₇ treatment, phenylalanine ammonia lyase(PAL) activity of pericarp increased by 55.3%, activity of polyphenol oxidase(PPO) and peroxidase(POD) decreased by 29.2% and 18.0%, and lignin content decreased by 4.1%-41.3%, thus enhancing cell flexibility and inhibiting fruit rust. GA₄₊₇ treatment had no significant effect on total sugar, soluble solids, protein, potassium content and edible rate(P>0.05), but significantly increased total acid content and vitamin C (P<0.05), with an increase of 40.0% and 11.8% respectively.【Conclusion】 Spraying exogenous 100 mg/L GA₄₊₇ can effectively reduce fruit rust occurrence and has no adverse effect on fruit quality, showing potential application value in high-quality banana fruit cultivation and production.