Study On The Species Of Anthracnose Pathogens And The Groups Genetic Diversity

Anthracnose is an important global disease mostly occurred in the hot and humid areas, such as the tropical and subtropical. In China, the occurrence is particularly serious, The disease could cause leaf spots, rotting, and it easily lead to the production of crops vegetables, etc. The annual losses caused by anthracnose are not possible to estimate, so it is quite necessary to study on China anthracnose pathogen taxonomic identification and population genetic diversity.In this study, a total of164different host disease samples were collected from Ya’an, Sichuan, Luzhou, Pan zhihua, Chengdu, Yibin, Xichang, Wenjiang, Shuangliu, Guangxi, Yunnan, Hainan, Hunan and other places. A total of102Colletotrichum spp. strains were collected through direct single-spore isolation and tissue isolation. In order to classify and identify the102Colletotrichum spp. strains, the morphological characteristics of them (the colony characteristics, shape and size of spores, characteristics of the appressoriums, etc.) were observed, and55strains were selected to do molecular identification and study the genetic diversity of them. CgInt and CaInt2the two specific primers were used to do species-specific detection, and the PCR amplification of the rDNA-ITS section were also used to do molecular identification. In addition, in order to study the genetic diversity of these55strains, the phylogenetic tree based on the rDNA-ITS section,β-tubulin-2-gene as well as calmodulin gene sequences were analysised, the pathogenicity test did by vaccinating the citrus, apples and peppers.The results showed that:based on their morphological characteristic, the102Colletotrichum strains were identified into three categories:Colletotrichum gloeosporioides (C. gloeosporioides), Colletotrichum acutatum (C.acutatum), and Colletotrichum truncatum (C.truncatum). The colony characteristics, morphology and size of conidium, acervuli’size showed some differences, showed that Colletotrichum sp. has an abundant diversity in morphology. There were95Colletotrichum gloeosporioides strains in the isolates, accounting for93.1%of all strains, was the dominant species;6strains were Colletotrichum acutatum, accounting for5.9%of the tested strains; only one strain numbered as YJH was identified as C.truncatum. Through analysising the phylogenetic tree based on the sequences of rDNA-ITS region,β-tubulin-2-gene, calmodulin gene, these three gene sequences all can reveal the differences between the Colletotrichum sp. species. The tested strains were clustered into three categories and this result were the same as the result of the morphological identification. But the rDNA-ITS region sequence and β-tubulin-2-gene sequence can only effectively reveal the interspecies differentiation of Colletotrichum sp. species, while could not effectively reveal the intraspecific differentiation of Colletotrichum gloeosporioid.es, Colletotrichum gloeosporioides strains were clustered into one class in a high similarity. The phylogenetic tree constructed by the calmodulin gene sequence could effectively reveal the interspecies differences in groups and C.gloeosporioides intraspecific genetic differentiation. Found no obvious correlation between the clustering results, host types and geographic sources in this study. The phylogenetic tree also showed that Colletotrichum sp. has a rich genetic diversity. Pathogenicity test result showed that the pathogenicity of the strains tested had pathogenicity differentiation. The pathogenic strains were classified into three different levels. The tested result suggested that all strains had pathogenic capacity for citrus49%of the strains’ pathogenic were strong. For peppers and apples, some strains had no pathogenicity; most of the pathogenic strains’ pathogenicity was moderate. There is no obvious correlation between the pathogenicity strength of trains, the geographical origin and the host species.