Evaluation Of Rice Blast Resistance And Green Control Technology Of Rice Diseases And Insect Pests In Hunan

Rice is the most important food crop.Rice disease and insect pests are important biological disaster and they affect high and stable yield of rice and food security.Green plant protection is an important goal as plant protection.In order to select and rationally utilize,genetic diversity and and avirulence gene composition of Magnaporthe oryzae and blast resistance evaluation of some main cultivars in Hunan were studied.Meanwhile,green integrated pest control trials on main diseases and insect pests of double cropping rice in Taojiang,Hunan were conductd out for clarifying the relative optimization of integrated green prevention and control technology.(1)8 pairs of SSR primers were used to analyze the genetic diversity of 49 M.oryzae of rice blast isolated and purified from several varieties of double cropping rice in Taojiang,Hunan Province.The results showed that 49 isolates could be divided into 10 pedigrees at the level of similarity coefficient of 0.70 by cluster analysis.The dominant pedigree I contained 18 isolates,accounting for 36.73%of the total number of bacteria tested;the pedigree III contained 9 isolates,accounting for 18.37%of the total number of bacteria tested;the pedigree IV contained 7 isolates,accounting for 14.29%of the total number of bacteria tested;the other pedigrees contained 1-4 isolates,accounting for 30.61%of the total number of bacteria.The genetic structure of M.oryzae in Taojiang,Hunan Province is complex,and very few isolates are far related.(2)19 specific M.oryzae were screened by using 18 NILs single-gene blast-resistant rice varieties to identify avirulence genes.The results showed that the pathogenicity of 19isolates ranged from 35%-75%,with an average pathogenicity of 49.86%,there were 3strong pathogenic isolates(pathogenic frequency>70%)which accounted for 15.7%of the total isolates;7 isolates were highly pathogenic(70%>pathogenic frequency?50%),accounting for 36.8%of the total isolates;9 medium pathogenic isolates(50%>pathogenic frequency?20%),accounted for 47.5%of the total isolates.The virulence frequencies of NILs rice isolates were deduced.The resistance gene whose virulence frequency was between 50%and 70%with medium virulence were pi-k~p,pi-z~5,pi-t,pi-sh and pi-5.The virulence frequency of the other resistance genes is less than 50%.The resistance genes of pi-3,pi-i,pi-11,pi-19 and pi-12 are excellent.(3)48 main cultivated rice varieties in Hunan were collected and identified for their resistance to blast by using 10 M.oryzae with clear avirulence gene.The results showed that the resistance of 48 cultivars to 10 isolates varied greatly,and the virulence frequency ranged from 0%-60%.The isolates showed strong pathogenicity to Fengliangyou 4,Yuehesimiao and Longliangyou 534,moderate pathogenicity to the other 34 varieties,accounting for 70.83%of the total rice tested,and weak pathogenicity to the other 11varieties,accounting for 22.91%of the total rice tested.Cluster analysis showed that 48cultivars could be divided into 31 pedigrees at the level of similarity coefficient of 0.70.According to the inference of"gene-to-gene"relationship between rice blast fungus and rice,the occurrence frequency of resistance genes Pi-1,Pi-a,Pi-7,Pi-3,Pi-i,Pi-11 and Pi-19 in all rice varieties is high,and they have good resistance;the frequency of occurrence of Pi-5,Pi-t and Pi-kp is low,and the resistance gene Pi-ta is the lowest and basically loses resistance.(4)The results of green integrated pest control experiment of double cropping rice in Taojiang field in Hunan province showed that the yield of each treatment plot was increased in varying degrees compared with the control area;the yield of double cropping rice was357.76 kg/667 m~2 and 325.3 kg/667 m~2 by chemical pesticides,respectively,which increased by 70%-100%compared with the control area.The combined control of chemical pesticides and biological pesticides has a prominent effect on rice diseases and insect pests.The yield of early rice and late rice increased by 137.71%and 184%respectively compared with the control area.The control effect of biological pesticides on early rice was poor,and the optimum medication scheme for late rice was nearly 40%higher than that of early rice.The application of long-acting and endogenous pesticides as"grafting agents"before transplanting can save about 40%-80%of the pesticide usage,and the effect of pesticide control at seedling stage is considerable.Seed dressing with biocontrol bacteria can promote the growth of seedlings.Biological pesticides have excellent disease control effect,and have little impact on the environment and natural enemies of pests.Chemical pesticides are more comprehensive than biological pesticides in the integrated control of pests,but Bacillus thuringiensis,Metarhizium anisopliae and other biological pesticides are also more prominent,suitable for alternative use.