Genetic Diversity Of Magnaporthe Oryzea And Green Control Of Rice Diseases In Taojiang,Hunan

Rice is one of the most important food crops.The rice blast,sheath blight and rice false smut are main diseases of rice,posing serious threat to high and stable yield of rice.In this study,we estimated the genetic diversity of Magnaporthe oryzae strains in Taojiang and the rice blast resistance of the mainly-planted rice varieties in Hunan province,with the aim to provide scientific proof for the rational distribution of rice varieties against to blast.Meanwhile,green prevention and control technique including compatible biological and chemical control measures were studied for control of the rice blast,sheath blight and rice false smut diseases,in order to reduce the use of chemical pesticides,make the environment and ecology more safe,and the economic benefit more remarkable.The main findings are as follows:1.Rice samples infected by M.oryzae were collected from Taojiang in 2019,and 120strains were obtained by single spore isolation.All strains could grow on tomato oat medium and produce conidia.However,there were significant differences in growth rate and sporulation among different strains.Among these,strain 006 grew the fastest,which was8.83mm/d.The slowest was strain 020,which was only 4.62mm/d.No.009 strain produced the most conidium,which was 17.53×10~5/m L.Strain 052 produced the least conidium,which was only 0.11×105/m L.2.Genetic diversity of the 120 strains was analyzed by PCR amplification using 8 SSR primer pairs.At the 0.70 similar level,the 120 strains were divided into 10 genealogies.The dominant genealogies wereⅠandⅤ,each of which accounted for 20%of the total number of strains.Ⅵwas the subdominant genealogy,accounting for 12.5%of the total strains.The proportion of other genealogy accounted for 10%to 2.5%.The genetic diversity of M.oryzae strains in Taojiang of Hunan Province is larger and abundant.3.Forty mainly-planted rice varieties in Hunan province were collected,and their resistance against to rice blast were tested using 40 single-isolated M.oryzae strains.Among these,Yuehe Si Miao,C liangyou 87 and Jingliangyou 1998 had the strongest rice blast resistance,with the antifungal frequency exceed 60%.The resistance frequencies of Chuangliangyou Yinhuazhan,Y liangyou No.1,Quanyou 33,Huiliangyou Youhang 1573,Liangyou 671,Shengtai you 9712 and Yliangyou No.6 were less than 20%,thus,these varieties should not be planted in the rice blast endemic areas.4.In the study of green prevention and control of late rice diseases in Taojiang,three biocontrol bacteria JN005,JN369 and YN145 had better comprehensive control effects on sheath blight,leaf blast,panicle blast and rice false smut diseases.Biological agent 37%Jing gang Bacillus cereus WP had the same effect as chemical fungicide.This study indicated that microbial preparation and bio-fungicide could replace the use of chemical fungicide for once or twice.Therefore,the rational or alternate use of biological and chemical fungicides could reduce the use of chemical pesticides and achieve the goals of efficiency,environmental protection and ecological friendliness in the integrated green prevention and control of rice disease.