Fine Mapping Of A Novel Resistance Gene Xa39 For Rice Bacterial Blight And Marker-assisted Selection Breeding

Bacterial blight(BB),caused by Xanthomonas oryzae pv.oryzae,is a rice disease worldwide.For controlling this diseases,developing resistant cultivars is the most economic and effective approach.In the previous study,a novel reisitance gene from a BC1F4 population derived from the cross between donor PSBRC66 and recipient Hang-Hua-Zhan has been identified and was designated Xa39.This gene provides rice breeders a new option to incorporate BB resistance into newly developed cultivars a since this gene is a single completely dominant gene resistance with broad resistance spectrum.In this study,Xa39 was fine mapped using F2 population,effectiveness of two closely linked molecular markers RM26985 and RM206 were evaluated by four breeding populationas,and resistant materials carring Xa39 were constructed.The main results are as follows:1.Using Bulked Segregation Analysis(BSA)to screen 516 pairs of SSR markers,46 pairs and 30 pairs Indel markers and 30 self-designing design markers,we constructed molecular markers linkage map by molecular markers tightly linked with Xa39,the gene is located on chromosome 11 of rice,between molecular markers RM26985 and DM13,and the range of 97.4 kb to predict 10 candidate genes.2.Combining artificial inoculation with phenotype identification we used RM26985 and RM206 closely linked with Xa39 gene,to evaluate of selective efficiency of molecular markers linked with Xa39,The results showed that the accuracy of marker RM26985 for MAS was 95.81% and that for marker RM206 was93.61% in the four populations.The accuracy of two markers RM26985 and RM206 for MAS were up to 95.35%.Therefore,RM26985 and RM206 can be used as effective markers in MAS for Xa39 in rice breeding program.3.Xa39 has been used to develop BB-resistant hybrid parents based on marker assisted selection,and resistant lines BC3F2 of four hybrid parent backgrounds have been obtained.