| Magnaporthe oryzae is one of the most widespread and destructive diseases in rice, and the most effective and economical ways of controlling blast disease are breeding and planting the various resistant cultivars rationally. However, the highly pathogenic variation and complex genetic diversity of the M. oryzae often leads to the resistance breakdown of the cultivars due to new blast fungus pathotypes. Therefore, it is great significance for the breeding and utilization of resistant cultivar to study on identification of resistance rlast genotypes and pathogenic avirulence genes and analysis of the genetic diversity on M. oryzae.The thesis, by the application of in vitro inoculation method with 22 blast fungus strains known avirulence gene identified the resistant genotypes of the 88 rice cultivars. The result suggested that the frequency of 7 cultivars against 22 blast fungus strains reached 80%, accounting for 7.95% of the total,43 had 60%-80%, accounting for 48.86%,35 hold between 40%-60%, accounting for 39.77% and 3 below 40%, accounting for 3.41%. Based on the longest-distance-cluster analysis at the similarity level of 0.7, the 88 rice cultivars can be classified into 56 groups, in which 13 cultivars' resistant genotypes in 9 groups were identified, while the other 47 cultivars was unknown.The the genetic diversity of the 162 isolates of M. oryzae from Taojiang nursery and Liuyang nursery by using 10 pairs of SSR primer were analyzed. According to the UPGMA clustering analysis,162 isolates can be classified into 23 lineages at the 0.8 similarity level, among which L01 is the superior one, accounting for 72.8%. In the two blast nursery, lineages, L02, L04, L07, L13, L14 and L20 had some simultaneous isolates, but L05 or L06 only distributed in the one blast nursery. The blast fungus lineages in the two blast nursery had not only with the common superior genealogy L01, but also with their unique ones. For instance, L03 and L05 lineages were only in Taojiang blast nursery, while L09 and L10 genealogies fell in Liuyang blast nursery. Therefore, the genetic composition of the M. oryzae in the above two nursery is not only featured with consistency but also with particularity.Avirulent genes of 154 blsat fungus isolates were identified by 18 NILs known blast resistance genes. The results indicated that Avr-Pil2, Avr-Pil9, Avr-Pia, Avr-Pik, Avr-Pi-kh, Avr-Pi-sh, Avr-Pil, Avr-Pi3 and Avr-Pi9 had higher frequencies in the tested isolates. Based on virulence for 18 NILs,154 isolates for Pi-3, Pi-9, Pi-12 and Pi-19 were low, that explain these R gene have wider anti-blast fungi spectrum. So these resistance genes can have well utilization value in controlling blast in Hunan.Blast resistance of 16 leading cultivas in Hunan were test by combining both the in vitro inoculation and the natural nursery identification method of the rice blasts. The result indicated that there exists significant positive correlation between the leaf blast incidence and neck blast ones, and their regression equation is y=0.9+2.6125x with the correlation coefficient, r1=0.6778 at p<0.05),r2=0.8325 at p<0.01, respectively. And there also exists significant positive correlation between the severity of leaf and neck blasts and pathogenic frequency of 22 strains to the 16 cultivars in in vitro inoculation, with r1=0.93 and r2=0.80, respectively. |
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