Clarification Of Rice Blast Resistance Genes In Shuhui498 Parent Of Hybrid Rice

Rice blast is the most serious fungal disease of rice,including seedling,leaf,node and panicle blast,which endangers the whole growth and development period of rice.Reasonable prevention and control measures should be adopted to reduce the harm of rice blast outbreak,so as to prevent economic losses of rice production.At present,the most feasible,economical,safest and greenest means is to cultivate rice blast resistant varieties by using blast resistance genes.Therefore,the exploration of rice blast resistance genes and the analysis of resistance molecular mechanism are the basis of promoting rice blast resistance breeding and solving the"bottleneck"problem of rice blast.In order to further explore the rice blast resistance gene resources,the rice blast resistance gene contained in R498 was analyzed by using the recombinant inbred line population constructed by the backbone parent Shuhui498（R498）and susceptible parent Yihui 3551（Y3551）with reference genome sequence.The new blast resistance genes contained in R498 were mapped and candidate genes were screened.The main research results of this paper are as follows:（1）The resistance spectra of R498 and Y3551 were determined using 15representative rice blast strains from Hunan Province.The results showed that R498 had a wider resistance spectrum than Y3551.A recombinant inbred line（RIL）population of F₁₀,which was constructed from R498 and Y3551 hybrids,was inoculated with R498 and Y3551 hybrids of 152 and 160,respectively.The results showed that the population had a 1:1 resistance ratio to 160 strains,and 3:1 to 152 strains.The results showed that there was only one main blast resistance gene against strain 160 and R498.For strain 152,R498,there were two main blast resistance genes.The resistance gene Pi-zt was found at Pi2locus in R498,which was resistant to both strains 160 and 152,and there was no significant linkage between the other resistance locus to 152 strains and the cloned blast resistance gene.（2）For 152 strains of the unknown resistance loci,the use of cloned molecular markers to rule out the site for the cloned gene,continue to design on 12 chromosomes of rice 2-3 uniform distribution of molecular markers,found only on chromosome 8 chain phenomenon,preliminarily determine the gene located on chromosome 8.（3）In order to further identify the new resistance locus against strain 152in R498,this study used the specific marker of Pi2 locus to detect and screened the recombinant inbred line RIL7 which did not contain Pi-zt gene but still showed resistance to strain 152.The BC₁F₂population constructed by RIL7 and parent Y3551 was identified by using 19 pairs of newly developed In Del markers in the initial mapping interval to identify 752 susceptible individual plants,and the target gene was finally located in the 98 kb interval between the short arm markers R43C-41 and R43C-48 on chromosome 8RIL7with parent parent Y3551.Nineteen pairs of In Del primers were used to identify 752 susceptible populations,and the target gene was located within the 98 kb physical range of two markers R43C-41 and R43C-48 on the short arm of chromosome 8.（4）The 98 kb candidate genes of R498 genome were predicted,and 16genes were found in this region,among which 7 encoded NLR protein.In susceptible parent Y3551,there were only 36 kb between R43C-41 and R43C-48 encoding 5 genes,of which only 2 encoded NLR protein.The amplification of NLR gene was widespread in 25 rice materials with high quality reference genomes.Through structural integrity analysis of genes encoding NLR protein,four genes（No.2,3,6 and 14）were selected as candidate genes for disease resistance.PCR cloning was successfully carried out and complementary vectors were constructed respectively.