| Gray leaf spot which happened more serious in the northest of China is an important worldwide disease of maize. The disease occurred year after year in Ya'an, Sichuan Province, and it caused serious consequence in corn production. The objectives of this study were to determine the resistance of maize varieties to Gray leaf spot caused by Cercospora zeae-maydis Tehon & Daniels and genetic diversity of the causal organism of the disease with RAPD markers.By the natural incidence of disease in the field, the resistance of 181 varieties were assessed to Gray leaf spot of maize in 2009. The results indicated that no immune cultivar was found. And 17 varieties showed highly resistant, accounting for 9.39%. The majority varieties appeared moderately resistant, susceptible or highly susceptible, accounted for 27.63%,35.91% and 20.99% respectively. The resistance of 112 varieties to Gray leaf spot was tested in 2010 by the same way. The resulted showed only Ya-yu26 was highly resistant and most were suceptible cultivars, accouting for 81.41%. Meanwhile, combined analysis indicated that the lesion length, lesion size and disease index were significantly different under different resistance levels.The genetic diversity of 49 strains which collected from different areas in Sichuan Province was analyzed by RAPD markers. The results showed that 38 bands were polymorphic stripes in 52 bands which were amplified by 6 primers, and the polymorphic rates were 73.08%, which revealed abundant genetic polymorphisms to some extent. Although genetic similarity coefficients (GS) were between 0.07 and 1.00, most of them were above 0.5. Cluster analysis showed that 49 strains could be divided into three groups and the cluster results had no significance association with cultivars isolated strains and geograghical position. |
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