Screening Of Resistant Resources And Primary Mapping Of Resistance Gene To Brown Planthopper In Common Wild Rice(Oryza Rufipogon Griff.)

Brown planthopper(BPH,Nilaparvata lugens St(?)l),one of the main pests of rice,affects the stable production of rice seriously.Breeding new varieties with resistence to brown planthopper is an economical and environmental strategy to control the BPH.Guangxi is the landing port for the BPH migrating from the Southeast Asia to China,and it is also a sure place for its return routine.During the long-term evolution,common wild rice(Oryza rufipogon Griff.)in Guangxi has developed into various types which are able to resist diseases and pests espacially the BPH.The common wild rice in Guangxi has been confirmed to be rich in resources to control the BPH,and several resistance genes have been exploited.In order to enrich the germplasm of resistance to BPH further,this essay mainly focus on that a set of resources of common wild rice in Guangxi was screened and then one of the resistant sources was used for preliminary gene mapping.The research results obtained are as follows:(1)Through the preliminary screening of 1221 accessions of common wild rice in Guangxi by Stem Evaluation Method(SEM)which was developed by our research group,58 resistant accessions were identified,accounting for 4.75%of the total,5 of which were highly resistant(HR),28 resistant(R)and 25moderately resistant(MR).Through repeated screening of the 58 resistant resources and once more repeated screening at adult growing stage,33accessions with stable resistance to the BPH were obtained and determinated as the final resistant sources.The analysis of the regional distribution of resistance resources showed that the frequency of resistance sources in Pingnan County in the lower reaches of Xijiang River was the highest(8.16%).The molecular marker analysis of resistant resources showed that the genetic diversity of 58resistant resources was rich.The actual number of alleles was 3.17,Shannon’s information index was 1.035,and the actual observed heterozygosity(H_o)was0.326,the mean expected heterozygosity(H_e)was 0.614,the genetic diversity index was 0.608,and the mean polymorphic information content was 0.536.(2)The common wild rice resistant resource GXU186 in Guangxi was crossed with 9311 to construct a mapping population for resistance genes to the BPH.The results of genetic analysis showed that the resistance of GXU186 to the BPH was recessive.A total of 562 polymorphic SSR molecular markers were used to screen the whole genome.Results showed that a new resistance locus was found between the molecular markers L2 and L3 on the long arm of chromosome 4,with the maximum LOD value 32.46 in this region and explaining 41.5%of contribution rate to the BPH.The results of this study show that Guangxi common wild rice is a kind of ideal materials for evaluating BPH resistant sources,and the obtained resistant resources can be used to exploit resistant genes and breed resistant cultivated varieties.The results were also testified that SEM has the characteristics of high efficiency,accuracy and flexibility,and has a bright application prospect in screening resistant resources,constructing resistant gene mapping populations and breeding resistant varieties.As population of common wild rice in Pingnan are rich in genetic diversity and high resistant frequency to the BPH,the distribution region of this wild rice becomes one of the crucial regions to further exploitation BPH resistant resources in the future.The resistance gene mapped from GXU186 and its tightly linked molecular markers can be significantly used to breed resistant rice varieties.