外源表没食子儿茶素没食子酸酯对甜瓜幼苗白粉病抗性的影响

白粉病是甜瓜生产中常见的真菌病害，严重影响果实的产量和品质。以甜瓜品种甜宝为试验材料，通过外源表没食子儿茶素没食子酸酯(EGCG)处理，探讨EGCG对甜瓜白粉病抗性的影响。通过二氨基联苯胺(DAB)染色和丙二醛(MDA)的测定结果表明，外源喷施EGCG能够减少白粉病侵染所引起的活性氧积累，MDA含量显著下降，甜瓜叶片细胞膜脂过氧化程度降低。甜瓜叶片抗氧化酶活性分析表明，外源EGCG预处理，过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、超氧化物歧化酶(SOD)、过氧化物酶(POD)4种主要抗氧化酶活性都显著升高。抗氧化酶活性也受到白粉病入侵的诱导，但外源EGCG预处理进一步促进了抗氧化酶的提高。利用实时定量PCR技术进一步分析了相关基因的表达情况，结果显示，抗氧化酶相关基因CmCAT、CmAPX、CmSOD、CmPOD也均受到外源EGCG的诱导表达。上述研究结果表明，外源喷施EGCG可以通过调控甜瓜叶片的抗氧化酶系统，降低白粉病侵染所引起的活性氧爆发，从而提高了甜瓜对白粉病的抗性。

Effects of exogenous epigallocatechin gallate on resistance of melon seedlings to powdery mildew

Powdery mildew is a common fungal disease in melon production, which seriously affects the yield and quality of melon fruit. Effects of exogenous epigallocatechin gallate (EGCG) on the resistance of melon to powdery mildew was explored in this study. The results of diaminobenzidine (DAB) staining and malondialdehyde (MDA) determination showed that exogenous spraying with EGCG could reduce the accumulation of reactive oxygen species caused by powdery mildew infection, accompanied with the content of MDA decreased significantly, and the degree of cell membrane lipid peroxidation was decreased. The analysis of antioxidant enzyme activities in melon leaves showed that the activities of catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and peroxidase (POD) were increased significantly after exogenous EGCG pretreatment. Antioxidant enzymes activity was also induced by powdery mildew invasion, but exogenous EGCG pretreatment will further promote the improvement of antioxidant enzymes. The expression of related genes was further analyzed by real-time quantitative PCR. The results showed that the antioxidant enzyme related genes CmCAT, CmAPX, CmSOD and CmPOD were also induced by exogenous EGCG. The above results revealed that exogenous spraying EGCG could reduce the reactive oxygen species burst induced by powdery mildew infection by regulating the antioxidant enzymes system to improve the resistance of melon to powdery mildew.