Isolation, Identification Of Causal Agents Of Maize Stalk Rot And Genetic Diversity Analysis Of Fusarium Spp.

With the changes of the cultivation methods and varieties, maize stalk rot has become increasingly serious and been a potential threat to corn(Zea mays L.)production in China. So study on dynamic changes and genetic variation within populations of pathogens is significant to understand the regularity of development of this disease and succession of pathogens and to find the effective control measures.This study was conducted to investigate and sample the maize stalk rot and isolate the pathogens from Northeastern Spring Corn Region, Huanghuaihai Summer Corn Region, Yunnan and Shanxi provinces. Several methods were used to identify the component structure of pathgens and the chemotype characteristics of Fusarium spp. populations. And population genetic diversity of Fusarium spp. populations caused maize stalk rot was preliminary studied by ISSR technique. Main results were showed below:In 2008 and 2009 growing seasons, the results from investigation in different corn producing regions showed that the dominant species of pathogens associated with maize corn stalk rot were not identical. This may arise from complexity of ecological environments, geographic and climate conditions across the sampling regions.A pair of published primers, Tri13F/Tri13R, were used to detect the mycotoxins deoxynivalenol (DON) and nivalenol (NIV) produced by F. graminearum. This primer pair amplified the fragments 234 bp and 415 bp in lengths, which were specific for Don and NIV, respectively. Primers Fum5F/Fum5R, which amplified a fragment 845 bp in length, were used to detect chemotype of fumonisin B (FB) from F. graminearum. In a total of 62 isolates of F. graminearum, 58, 6, and 3 isolates produced DON, NIV, and FB chemotypes, respectively. Enzyme-linked immunosorbent assay (ELISA) confirmed the results of PCR analysis for detection of DON and FB.Using 19 pairs of ISSR markers, the genetic diversity of 31 strains of F. verticillioides were assessed. A total of 117 alleles were produced from these strains. At each locus, the number of alleles ranged from 4 to 9 with an average of 6.16.These markers are highly polymorphic and can be used to analyze genetic diversity of F. verticillioides. Genetic diversity and clustering analyses of the 31 different isolates of F. verticillioides from 8 different regions indicated that the genetic diversity levels of populations from Beijing and Shandong were higher than those of other regions. The populations from Jilin and Liaoning provinces were closer than other populations.Using 14 ISSR markers, the genetic diversity of 115 strains of F. graminearum from 11 different regions were assessed. A total of 63 alleles were detected in these F. graminearum strains. Genetic diversity and clustering analyses of the F. graminearum stains indicated that the genetic diversity of the populations from Shandong, Jiangsu and Anhui provinces were higher than those from other provinces. The populations from Shandong and Henan provinces were closer than others populations. The strains of F. graminearum in the same cluster and the same region may different, indicating that F. graminearum exhibited obvious physiological differentiation.