Identification Of Pathogen Causing Maize Gray Leaf Spot And Genetic Variaty In C. Zeina Population

Gray leaf spot causes yield loss of corn severely. According to different pathogenic species, they were divided into two categories: gray leaf spot caused by Cercospora zeae-maydis and gray leaf spot caused by C. zeina. To further clarify the Cercospora species causing gray leaf spot of maize in the latest disease area, the happening of the disease and popular dynamic, this study identif ied the pathogen of gray leaf spot collected during 2013-2015 and the population genetic structure and molecular variation of C. zeina collected during 2008-2015. The main results are as follows:1. Cercospora zeae-maydis and C. zeina were the main pathogen of gray leaf spot in China.The 110 Cercospora strains, isolated from the samples of eleven provinces, were identified based the morphology, culture characters and molecular detection. 82 Cercospora strains were C. zeina, they distributed in Yunnan, Sichuan, Chongqing, Guizhou, Hubei, Shaanxi, Gansu, Henan, Hebei and Heilongjiang provinces; 27 Cercospora strains were C. zeae-maydis, they distributed in Heilongjiang, Beijing, Hebei, Shaanxi, Henan and Sichuan provinces while 1 Cercospora strain isolated from Yunnan was C. rodmanii. The results has been clear about the Cercospora species of the latest area.2. Gray leaf spot caused by Cercospora zeina was expanding to the north area quickly, it has threatened the production of the north spring corn.The identif ication of the pathogen further clarify the occurrence status quo of gray leaf spot. The main pathogen isolated in the north area was C. zeae-maydis. The main pathogen isolated from Yunnan, Guizhou, Chongqing and Sichuan was C. zeina. Both of the two pathogen were existed in Shaanxi and Henan. C.zeina come from the southwest area has crossed bashan mountain and qinling mountain to Shaanxi and Gansu, C.zeina come from Hubei has been introduced to the western region of Henan, it has caused severe losess in partial area.3. Yunnan was the birthplace of gray leaf spot caused by Cercospora zeina in China.Population genetics and polygene molecular detection(ITS、β-tubulin、H3、18sRNA、Actin) showed insignif icant genetic difference in C.zeina group, and the main var iation of C.zeina was within population; Gene flow existed between any other two populations and it was frequent between Yunnan and the other six provinces; C.zeina undergo a population expansion and it may happened in Yunnan; Yunnan had the highest genetic diversity, and Shaanxi had the lowest genetic diversity. The results indicated that Yunnan was the birthplace of gray leaf spot of other provinces.4. The variation of local population of Cercospora zeina was relative to colonization time, host species and environment.The genetic structure of Cercospora population showed that special population were appeared in Yunnan and Hubei which were different from the early population. The mutation showed that when the bacteria colonization in a region, the local population can form new difference geographic population under the action of host species and environment.