鼠李糖脂处理对早酥梨抗黑斑病的诱导作用及其机理

Inductive Effect and Mechanism of Rhamnolipid Treatment on Resistance against Black Spot Disease in‘Zaosu’Pear Fruit

为探讨生物源表面活性剂鼠李糖脂(rhamnolipids,RLS)对梨果黑斑病的控制效果及其机理,本实验以梨果黑斑病菌(Alternaria alternata)为研究对象,研究了RLS对梨果抗黑斑病的诱导作用及其机理。结果表明,质量浓度20 mg/mL RLS处理能有效增强早酥梨对A.alternata的诱导抗病性,处理12 d后,其病斑直径仅为对照组的64.29%。进一步研究发现,与对照组相比,RLS处理显著提高了梨果组织的苯丙氨酸解氨酶(phenylalanine ammonia-lyase,PAL)、肉桂酸-4-羟化酶(cinnamate 4-hydroxylase,C4H)、4-香豆酸辅酶A连接酶(4-coumarate coenzyme A ligase,4CL)和肉桂醇脱氢酶(cinnamyl alcohol dehydrogenase,CAD)的活力,以及总酚和类黄酮的含量,整体上显著提高了几丁质酶和β-1,3-葡聚糖酶的活力(P<0.05);提高了NADPH氧化酶(NADPH oxidase,NOX)、超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)、过氧化物酶(peroxidase,POD)活力及贮藏前期和中期H_(2)O_(2)和O_(2)-·的含量,同时,激活了活性氧清除系统抗坏血酸-谷胱甘肽循环(ascorbate-glutathione cycle,ASA-GSH),维持了梨果组织活性氧动态平衡,进而降低了梨果细胞膜透率和丙二醛(malondialdehyde,MDA)的含量。综上,RLS采后处理可通过调节梨果组织苯丙烷代谢、活性氧代谢及病程相关蛋白增强其抗病性。

We performed this study in order to evaluate the control effect and mechanism of the biosurfactant rhamnolipids(RLS)on black spot disease caused by Alternaria alternata in pear fruit.The results showed that RLS treatment at a mass concentration of 20 mg/mL effectively enhanced resistance to A.alternata,and the lesion diameter was only 64.29%of that of the control group at 12 days following the treatment.Furthermore,it was shown that compared to the control group,RLS treatment significantly increased the activities of phenylalanine ammonia lyase(PAL),cinnamate acid 4-hydroxylase(C4H),4-coumarate coenzyme A ligase(4CL),and cinnamyl alcohol dehydrogenase(CAD),as well as the contents of total phenols and flavonoids in pear fruit tissue.The activities of chitinase andβ-1,3-glucanase were significantly induced.The activities of NADPH oxidase(NOX),superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD),and the contents of H_(2)O_(2) and superoxide anion radical in the early and middle stages of storage were also increased by RLS treatment.Meanwhile,the ascorbate-glutathione(ASA-GSH)cycle was activated to maintain the dynamic balance of reactive oxygen species(ROS)production and scavenging in pear fruit tissue,and the membrane permeability and the content of malondialdehyde(MDA)were reduced.Collectively,this study suggested that post-harvest rhamnolipid treatment can enhance black spot disease resistance in pear fruit by regulating phenylpropane metabolism,ROS metabolism and pathogenesis-related proteins.