Identification And Genetic Diversity Of Cercospora Species Causing Gray Leaf Spot In Maize

Gray leaf spot,caused by Cercospora spp. is a destractive leaf disease, which caused yield lossand has become one of the main diseases in the world. In China gray leaf spot of maize has occurredin three major maize producing areas (northeast, Huanghuaihai and southwest maize zone), but stillnow there is not clear report for the pathogen causing the disease. The arm of the study is to undersdandthe Cercospora species causing gray leaf spot of maize in China and the genetic diversity of thepathogen population. The main results are as follows:1.136Cercospora strains, isolated from samples of Heilongjiang, Jilin, Liaoning, Inner Mongolia,Shandong, Hubei, Yunnan, were identified based the morphology and culture characters, and detectedwith the species-specificity primers. Of them,65strains were identified as Cercospora zeae-maydisTehon&Daniels), and71were Cercospora zeina Crous&U. Braun). It is first to report that C.zeae-maydis and C. zeina are tow species causing gray leaf spot of maize in Chian, and the first speciesis distributed in Heilongjiang, Jilin, Liaoning, Shandong and Inner Mongolia provinces as well as inYunnan before and the later is in Yunnan and Hubei provinces. Cercospora zeina is the first reportedin China.2. The strains of two Cercospora species grow at10~36℃temperature range with the optimumgrowth was at24～26℃, and the growth was slowly at10℃and36℃The strains can grow in pH4～12conditions, the optimum growth pH was6~7; At the same temperature and pH conditions, the growthrate of C. zeae-maydis was higher than C. zeina strainsin MLPCA medium.25℃within dark culturefor5d is a better condition for the sporulation. The pathogenicity is different among Cercospora strains.3.91Cercospora strains were analyzed for genetic diversity. Using18pairs of ISSR primers,98polymorphic bands were amplified, with average5.4polymorphic bands, of which84bands werepolymorphic markers, and polymorphism rate reached85.7%. In the nucleotide sequence of C.zeae-maydis and C. zeina,(AG)nand (GA)ndistribution is relatively common.91strains were dividedinto2groups with7subgroups. C. zeae-maydis and C. zeina are responsible to two groups respectively,and sever subgroups were related with the strains from different provinces respectively.