李果实褐腐病病原菌产生细胞壁降解酶条件优化及其致病机理

Optimization of Culture Conditions of Monilinia fructicola for the Production of Cell Wall Degrading Enzymes and Their Involvement in Brown Rot Pathogenesis of Postharvest Plums

研究李果实褐腐病病原菌产生细胞壁降解酶的种类及其产酶最佳条件,并探讨其导致果实发病的作用机制。以Monilinia fructicola为研究菌株,通过单因素试验和正交试验优化M.fructicola产生细胞壁降解酶条件;通过损伤接种粗酶液,研究其对李果实的致病作用。结果表明:M.fructicola产细胞壁降解酶的最佳条件为:培养时间6 d、培养基pH 6.0、碳源为3.5%蔗糖、氮源为2.5%硝酸钾;粗酶液处理能够导致李果实发生褐腐病,同时引起果实多聚半乳糖醛酸酶(polygalacturonase,PG)、果胶甲基半乳糖醛酸酶(pectin methylgalacturonase,PMG)活力的上升,使果实原果胶物质转化为可溶性果胶,同时造成其纤维素含量下降,加速果实的软化腐烂进程。

The aims of this study were to optimize the culture conditions of Monilinia fructicola for the production of cell wall degrading enzymes(CWDE)and to clarify the role of the culture supernatant obtained as crude CWDE in the pathogenesis of brown rot caused by Monilinia fructicola in postharvest plums.The optimization of the culture conditions was carried out using one-factor-at-a-time and orthogonal array design methods.Besides,the pathogenesis was investigated by wounding and inoculating plum fruits with the crude CWDE and observing the incidence of brown rot.The results showed that the optimal culture conditions were as follows:culture time,6d;pH,6.0;3.5%sucrose as carbon source;and2.5%KNO3as nitrogen source.The crude enzymes produced by M.fructicola could cause brown rot of plum fruits.In addition,the activities of polygalacturonase(PG),pectin methylgalacturonase(PMG)in the fruits inoculated with the crude enzymes were enhanced,thereby leading to the conversion of insoluble protopectin to soluble pectin and cellulose reduced cellulose content and consequently accelerating the softening and rotting process.