Diversity Of Pathogen Of Corynespora Leaf Spot On Vegetables In China

Corynespora leaf spot caused by Corynespora cassiicola occurred heavily, having a significantimpact on production of vegetables and causing huge economic losses. Based on taxonomy, this paperstudied the diversity of C. cassiicola isolated from different sources, by analyzing phenotypiccharacteristics, pathogenic differentiation and phylogenetic analysis. The main results were as follows.1. Corynespora leaf spot had become a main disease of vegetables in China based on theinvestigation in9provinces including Hebei, Shandong, Hainan, etc, during2010-2012.70strains of C.cassiicola were isolated from11hosts of5families, through tissue separation and morphologicalidentification.2. C. cassiicola was divided into6types based on colony morphology. Culture morphology of C.cassiicola was associated with hosts, but irrelevant to district sources. By measuring growth rate ofstrains at23℃and33℃, the sensitivety of C. cassiicola isolated from various hosts to temperature wassignificantly different, with obvious correlation to the hosts, but independent of geographical sources.3. Pathogen of Corynespora leaf spot on vegetables in China had2pathotypes through artificialinoculation on10hosts of4families. Pathotypes were closely related to the hosts. Hosts of pathotype1were mainly Leguminosae, Euphorbiaceae and flowers, showing higher pathogenicity on cowpea andpea bean, while hosts of pathotype2were mainly Cucurbitaceae and Solanaceae, showing higherpathogenicity than isolates from pathotype1.4. Through phylogenetic analysis, pathogens of Corynespora leaf spot on vegetables in China weredivided into5genetic groups, which were closely related to pathotypes and phenotypic characterstics.Hosts from genetic groups2and5were mainly Cucurbitaceae, hosts from genetic group3were mainlyCucurbitaceae(Cucumis sativus and Momordica charantia) and Solanaceae(Solanum melongena), whilehosts from genetic group4were mainly Solanaceae(Capsicum annuum and Solanum lycopersicum).Strains from various geographical sources and the same host distributed in various genetic groups,showing that genetic groups were not related to geographical sources.With the pathogen of Corynespora leaf spot colleted from vegetables growing areas, flowers andrubber in China, comprehensive utilization of phenotypic characteristics, pathogenicity test, andphylogenetic analysis using EF1alpha and actin gene, we analysed population differentiation of C.cassiicola from various hosts and areas in China, revealing the host specialization and genetic diversity,investigating the relationship between the pathogenicity differentiation and genetic diversity. The resultsprovided the theoretical reference for the intraspecific differentiation of C. cassiicola and laid thefoundation for breeding the stable and effective resistance varieties.