Development Of Molecular Markers Linked To Me1 Gene With The Nematodes Resistance In Pepper

Root-knot nematode is one of the main disease of pepper, having brought increasingly serious harm. The most effective way to control this disease is breeding resistant pepper. Traditional breeding has the disadvantage of long cycle and high cost, and molecular mark assisted breeding will greatly improve efficiency of breeding. EST-SSR is a new type of molecular marker developed from the databank of sequence of expression sequence tags (EST) and cDNAs. As a new kind of molecular marker, EST-SSR markers have more advantages than the traditional genomic-derived SSRs because they are part of expressed genes. Therefore, EST-SSRs might be involved in gene functioning directly or indirectly. The ability of SSR markers will be greatly enhanced.In this study, we analyzed SSR resource of ESTs data in Capsicum, and preliminary developed soMe EST-SSR markers, and identified molecular markers linked to the dominant resistant gene Me1 laying the foundation for resistance breeding. The main results were following.1. In this report,19173 ESTs of Capsicum annuum were downloaded from NCBI, from which 612 SSRs were screened, by using software SSRIT, and the frequency was 3.19%.51 types of repeat motifs were detected and the dominant type was trinucleotide which occupied 60.46% out of total SSRs. Predominant motifs of di-, tri-, tetra-, penta-and hexa-nucleotide repeats were AG/GA/CT/TC, AAG/AGA/GAA/CTT/TTC/TCT, TAAT, ATATA and CTGCTC, with the frequencies of 13.40%,16.18%,1.80%,3.27% and 2.12% respectively. The repeat number of pepper EST-SSR was mainly 5-10 and the motif length ranged from 15bp to 20bp.2. We designed 357 candidate priMer pairs for 576 EST-SSRs. Under optimal PCR conditions, The amplification and polymorphism displayed by these priMers in 6 varieties of pepper were detected by using silver staining of non-denaturing polyacrylamide gel.337 priMer pairs (94.40%) showed clear amplification, and 75 of them (21.01%) demonstrated polymorphism.3. The materials were F1 and a F2 population from PM217 with the resistant gent Me1, and the typical susceptible variety QieMen. Using artificial inoculation,2000 eggs of southern root-knot nematodes per plant were poured to investigate the number of root knots after inoculated for two months. Base on the results of the investigation, a resistance group and a sensitive group were divided with 'BSA' Methods to search for the EST-SSR polymorphic priMer combinations priMer 118,141,142 and 211, and tentatively naMed EST-SSR markers 118,141,142 and 211.4. By the software JoinMap V3.0, the relationship of 4 EST-SSR molecular markers and resistant segregation of F2 population were analyzed.The results indicated that the distance between the EST-SSR molecular markers141,118 and 211 and the nematodes resistance Me1 gene in pepper were 6.984cM,18.684cM and 29.310cM respectively.