The gray leaf spot caused by Cercospora zeina has become a serious disease in maize in China.  The isolates of C. zeina from Yunnan, Sichuan, Guizhou, Hubei, Chongqing, Gansu, and Shaanxi were collected.  From those, 127 samples were used for genetic diversity analysis based on inter-simple sequence repeat (ISSR) and 108 samples were used for multi-gene sequence analysis based on five gene fragments.  The results indicated that populations of C. zeina were differentiated with a relatively high genetic level and were classified into two major groups and seven subgroups.  The intra-population genetic differentiation of C. zeina is the leading cause of population variation in China, and inter-population genetic similarity is closely related to the colonization time and spread direction.  The multi-gene sequence analysis of C. zeina isolates demonstrated that there were nine haplotypes.  Genetic diversity and multi-gene sequence revealed that Yunnan population of C. zeina, the earliest colonizing in China, had the highest genetic and haplotype diversity and had experienced an expansion event.  With the influence of the southwest monsoon in the Indian Ocean, C. zeina from Yunnan gradually moved to Sichuan, Guizhou, Shaanxi, Gansu, and Chongqing.  Meanwhile, C. zeina was transferred directly from the Yunnan into the Hubei Province via seed and then came into Shaanxi, Henan, and Chongqing along with the wind from Hubei.

Northern corn leaf blight (NCLB), caused by the heterothallic ascomycete fungus Setosphaeria turcica, is a destructive foliar disease of maize and represents a serious threat to maize production worldwide. A comparative proteomic study was conducted to explore the molecular mechanisms underlying the defense responses of the maize resistant line A619 Ht2 to S. turcica race 13. Leaf proteins were extracted from mock and S. turcica-infected leaves after inoculated for 72 h and analyzed for differentially expressed proteins using two-dimensional electrophoresis and mass spectrometry identification. 137 proteins showed reproducible differences in abundance by more than 2-fold at least, including 50 up-regulated proteins and 87 down-regulated proteins. 48 protein spots were successfully identified by MS analysis, which included 10 unique, 6 up-regulated, 20 down-regulated and 12 disappeared protein spots. These identified proteins were classified into 9 functional groups and involved in multiple functions, particularly in energy metabolism (46%), protein destination and storage (12%), and disease defense (18%). Some defense-related proteins were upregulated such as β-glucosidase, SOD, polyamines oxidase, HSC 70 and PPIases; while the expressions of photosynthesis- and metabolism-related proteins were down-regulated, by inoculation with S. turcica. The results indicated that a complex regulatory network was functioned in interaction between the resistant line A619 Ht2 and S. turcica. The resistance processes of A619 Ht2 mainly resided on directly releasing defense proteins, modulation of primary metabolism, affecting photosyntesis and carbohydrate metabolism.