Mapping Of Resistance Genes For Common Bacterial Blight In Common Bean(Phaseolus Vulgaris L.)

CBB is a serious disease in the production of common bean. Screening resistant germplasms, developing linkage markers, cloning resistance gene, breeding and planting resistance varieties is the best way to control CBB. For exploring the resistance gene, this research was focused on germplasm resources screening, population construction, map construction and QTL mapping. The major results are as follows:1. Resistant germplasm resources screeningBy using ground storage water to moisturize after needle method, 661 accessions were evaluated for resistance to CBB in the greenhouse. The results showed that inoculation was reliable. Combined with moisturizing of ground storage water after inoculation by needle method, we found 5 resistant, 82 moderately resistant, 400 susceptible and 174 high susceptible accessions of germplasm resources.2. Segregation population constructionWe constructed an F2 population between Longyundou5 and Longyundou4. This population contained 463 plants. This population was evaluated by needle method for resistance to CBB. As results, the absolute value of skewness was less than 1 according to the phenotypic results at 14 d and 21 d after inoculation. It can be used to QTL mapping.3. Map construction2,802 different SSR motifs were mined based on genomic sequences, 168 markers showed polymorphisms between two parents. In addition, we screened 49 polymorphism primer sets of 1,381 public markers. According to the different of F1 plants, we explored 217 polymorphisms markers in F2 populations and removed serious distorted segregation markers, then constructed genetic linkage map and integrated into one map by QTL IciMapping v4.0. Finally, we obtained an integrated genetic map, which contained 212 SSR markers.4. QTL mapping and genetic analysisCombined with the results of the phenotype and genetic map, we detected two single-QTLs at both 14 d and 21 d after inoculation by QTL IciMapping v4.0. One was located at B08 between p8s214 and p8s193 that explained 4.2% and 3.8% of the phenotypic variation at 14 d and 21 d, respectively. The other was located at B11 between p11s225 and p11s229 that explained 9.2% and 5.7%.By analyzing epistatic-effect, 35 and 58 epistatic-QTLs were identified at 14 d and 21 d. 2 epistatic-QTLs(E-Q1 and E-Q2) were detected at both days. E-Q1 was scanned between the positions p8s192/BMg985 and p3s3/p3s9, which explained 18.8% and 43.5% of the phenotypic variation at 14 d and 21 d, respectively. E-Q2 was scanned between the positions p3s262/p3s185 and BMg1019/p4s19, which explained 24.8% and 50.4%.