Study On Pathogen Of Small Leaf Spot Disease And The Harm Of Leaf Spot Disease On Maize In Ya’an

During2010and2011, leaf blight diseases were investigated on maize in Ya’ an. The survey shows that there were some small leaf spot diseases caused by several fungi besides northern corn leaf blight(Exserohilum turcicum) and gray spot disease (Cercospora zeae-maydis) in Ya’ an. In2010, northern corn leaf blight was mild occurrence, whereas small leaf spot and gray spot disease were vere serious in Baoxing. In2011, small leaf spot and gray spot diseases were slighter than2010after treatments, especially in Lushan and Baoxing.The relationship between elevation and northern corn leaf blight is not obvious, however there were a positive correlations of between elevation and occurrences of small spot leaf and gray spot disease, especially gray spot disease. It showed that higher elevation correspond to heavier condition.22species of fungi were identificated from corn leaf by4methods, which are moisturizing observation, microscopic examination, tissue separation and tissue separation without sterile. They included Fusarium, Bipolaris spp, and so on,29isolates were obtained from small leaf spot and identificated. By comparing colony morphology, colony growth rate, spore morphology, spore germination, shape of spot, the results showed that the dominant isolates had slow growth rate, straight spore, two ends of germination, and caused the small strip spot, the strains could be divided into3categories by rDNA-ITS and elongation factor sequences detection. The first kind of strains is Bipolaris maydis which was dominant group causing southern corn leaf blight. The second kind of strains was Bipolaris sorokiniana. The third kind of strains was Bipolaris zeicola which could cause small stripe type leaf spot disease.