Study On Biological Characteristics And Genetic Diversity Of Cochliobolus Heterostrophus In Fujian Province

Southern corn leaf blight(SCLB)caused by Cochliobolus heterostrophus(Drechsler)Drechsler,is an important disease in the production of corn.To further know the characteristics of C.heterostrophus population in Fujian province,the biological characteristics and genetic diversity of 131 C.heterostrophus isolates from 7 regions in Fujian province,including Nanping,Ningde,Fuzhou,Sanming,Putian,Longyan and Zhangzhou,were studied in this paper.The main results were as follows.1.The results showed that the mycelial growth rate,sporulation and conidia germination rate of 131 isolates were in the ranges of 7.5-14.0 mm/d,4.2×10~5-117.0×10~5 mL-1 and 57.0-100.0%,respectively,with the mean values of 11.70 mm/d,37.50×10~5 mL-1 and 92.00%,in the orders.The single and double germ tube ratio in germinated spores of each isolate ranged from 0.15 to 3.56 and with the mean value of 0.7.2.The pathogenicity of 131 C.heterostrophus isolates was determined on main corn varieties by using the inoculation methods of spraying conidial suspension at the stage of corn seedling.The results indicated that the disease index of tested isolates ranged from 25.82 to 71.21,with the mean value of 48.80.The frequency of isolates,showed weak,moderate and strong pathogenicity,were 22.14%,71.75%and 6.11%,respectively,the pathogenicity had no obvious correlations with mycelial growth rate,sporulation and conidia germination rate of isolates.3.The ISSR-PCR amplification system for C.heterostrophus was established,13 polymorphism primers were selected and used to amplification of 131 DNA samples,a total of 141 DNA bands were amplified,among which 100%were polymorphic,the results indicated that there were abundant genetic polymorphism in isolates of C.Heterostrophus in Fujian.By cluster analysis,all tested isolates could be classified into 6 groups at level of genetic distance 0.757,groups ?,?,?,?,? and ? contained 38,12,13,33,34 and 1 isolates,accounted for 9.16%,9.92%,25.19%,25.96%and 0.76%of all isolates,respectively.The preliminary analysis showed that genetic clustering has a certain correlation with geographic origin of isolates,however,there were no obvious correlation between genetic clustering and biological characteristics of isolates,including their pathogenicity,mycelial growth rate,sporulation and conidia germination rate.