The Analysis Of Rice Blast Resistance For Main Rice Breeding Parents In Southwest In China

Rice (Oryza sativa L.) is one of the most important staple food crops in the world. The production of rice affects the security and stability of food directly. Rice blast caused by Magnaporthe grisea is one of the most devastating disease of rice. It reduces the yield of rice every year largely. How to control this disease in effective ways have drew widespread attention of plant pathologists and breeders. For a long-term sense, resistant breeding is one of the most effective ways to prevent and control rice blast.With the report of new rice resistant genes, many breeders have breeded a few new rice varieties (lines) with broad-spectrum resistance to Magnaporthe grisea by combining traditional methods with genetically modified technology. In the past decades, there are 18 resistant genes for rice blast have been cloned. All these will make great contribution to breed new high-resistant rice varieties (lines). According to the reported references,11 pairs of pimers were designed to test the distribution of 8 rice blast resistant genes in our 36 testing rice lines.70 blast strains were spraied on the 36 rice lines at the seedling stage. And the resistant spectrum of every line was investigated. Cluster analysis was conducted based on the resiastant phenotypes and the results of RGA-PCR by 9 pairs of RGA primers.The purpose of this study is to find the resistant spectrum of the 36 lines, analysis of the source and the polymorphism of genetic resistance of these 36 testing lines. And the results are as follow:The result of resistant spectrum testing shows that Lijiangxintuanheigu (LTH) are absolute susceptibility to all rice blast strains.The resistant frequencies of 18B,Chuannong1B,Chuannong4B and DiguB are the highest reaching up to 90%. The resistant frequencies of R557,Minghui63 and R9311 are the lowest only about 40%. The resistant spectrum of the other lines are different from each other. And the average resistant frequency of maintainer lines is higher than restorer lines. The rate of neck blast for every line is quite different, ranging from 2.78% to 100%. The Channong 1B, DiguB, Kanghui lhao and R1088 have strong resistance to neck blast.The resistance to neck blast of Jin 23B and Minghui 63,ect. are poor, the resistance to neck blast of LTH and D62B are the poorest.The clustering based on the results from phenotypes of leaf blast resistance indicates that Chuannong 1B, Chuannong 4B and DiguB can be clustered together with the euclidean metric of 2.3. With the euclidean metric of 4.158, almost all the maintainer lines are divide into one group and the restore lines are divided into another group. This result indicates the diversity of genetic relationship in these two different lines. The resistant phenotype of D62B are different from other lines and more close to CK. The results of PCR by special primers shows that Pid3 are widely existing in these lines. Only R727, R498 and R137 contain Pizt. The frequencies of the resistant gene Pid2,Piz,Pikm,Pib,Pi-tαand Pi5 in these 36 lines are 25.00%,33.33%,36.11%,6.61%,0.56%,44.44%,respectively. R727, R498, R137, JR71 contain 5 blast resistant genes from the results of PCR by special locus pirmers. And Mianhui725, R9311, ZhensanB, II-32B and Jin32B only contain Pid3. The the numbers of the the resistant genes in other lines are ranging from 2 to 4.The results of RGA-PCR show that the amplification bands of every line are different form each other by different primers.The total number of amplification bands for 9 RGA primer are 593.462 bands of them are polymorphic and the frequency of polymorphic band is 85.71%.The amplification bands of primer XLRR are the highest and reach to 104. On the contrary, the amplification bands of primer N1 are the lowest and the polymorphic frequency of the amplification bands by primer Pt is the best.For all the primers, the amplification bands of Mianhui725 are the least and the polymorphy of amplification bands is the lowest. The results of clustering analysis indicate that all the lines can be divided into diffierent sub-groups with different primer. But all the lines can be devided into two groups.All these indicate the diversity of genetic background of every lines.And the genetic resistance of Mianhui 725 is widely different from the others. Meanwhile, the clusterring result is apt to divid maintainer lines and restore lines into 2 different groups.