Research On The Resistance Of Chuanxiangyou3 To Rice Blast And The Perfect Stage Of Pathogenic Strains

Hybrid rice was cultivated extensively in Sichuan from 1980's, which contributed much to the society developing, but rice blast was an important disease in its' production all along. By artificial infection in seedling stage, the resistance spectrum and resistant inheritance of Chuanxiangyou3,and the physiological races, pathogenicity of the pathogenic strains for Chuanxiangyou3 were analyzed; Finally, with two pairs of standard isolates, the perfect stage of Magnaporthe grisea was studied in this paper. The results as below:115 isolates ,effectively inoculated on Chuanxiangyou3, which belonged to ZA, ZB, ZC, ZF, ZG 5 groups, could be subdivided into 24 Chinese races. ZB was the most dominant group with the frequency of 57.39%, followed by ZA with the frequency of 37.39%. the frequency of ZC, ZF, ZG was 2.61%, 1.74%, 0.87% respectively, it was much lower than that's of ZA and ZB. ZA13 and ZB13 were the most dominant races, both with the frequency of 22.61%. ZB group differentiated greatly including 14 races.Chuanxiangyou3 was an intermediately resistant rice variety with the total resistant rate of 76.52%,and the resistant rate to ZA, ZB, ZC, ZF, ZG group was 65.12%, 81.82%, 100%, 100%, 100%, respectively. When comparing with the restoring line CDR448, its' resistance predominance was 42.09%, 12.70%, 19.97% to ZA, ZB group and all strains. Further research on the resistant inheritance of Chuanxiangyou3 indicated that its' resistance was controlled by one dominant gene.The 27 pathogenic strains for Chuanxiangyou3, isolated from more man 10 rice varieties such as Gangyou725 in 8 counties(towns) of Sichuan, belonged to ZA, ZB group,ZA₁,ZA₅, ZA₁3, ZB₁,ZB₅,ZB₇, ZB₁3 7 races. ZA₁, ZA₁3, ZB₁ were the main pathogenic races, with the percentage of 18.52%, 29.63%, 22.22% respectively, which added up to 70.37%, the percentage of ZA₅, ZB₅,ZB₇ amounted to 18.52%, and ZB13 with the percentage of 11.11%. The virulence of the 27 pathogenic strains was strong, the frequency of pathogenicity to 27 hybrid breeding materials rangedfrom 77.78-100%, with the average of 90.54%. The pathotype of the strains in 1 race was different from each other, 8 ZA13 strains have the frequency of similar pathogenicity of 70.37-96.30%, and that's of 6 ZBi strains of 77.78-96.30%.Mating type and fertility of 132 isolates were tested with 4 standard isolates Kat3-Guylland 6023-2539w,47 of them were fertile, the rate of perfect stage formation was 35.61%.Among the fertile isolates: 34 isolates, with the frequency of 72.34%, belonged to Matl-2, 13 isolates, with the frequency of 27.66%, belonged to Matl-1; As regard to sex, 2 were female, 8 were hermaphroditic, 37 were male, with the frequency of 4.26% > 17.02%^ 78.72%, respectively. Among the 27 pathogenic strains for Chuanxiangyou3, 5 were fertile, with the sterility percentage of 18.52%, 4 of Matl-2, 1 of Matl-1; 2 have generated matured asci and ascospores when cross with Kat3, which might be good materials for pathogenicity genetics of Magnaporthe grisea research.