Genetic Mapping of Quantitative Trait Loci for Bacterial Wilt Resistance in Pepper (Capsicum annuum L.) using Genotyping-by-Sequencing

Bacterial wilt (BW) caused by Ralstonia solanacearum is one of the most common soil-borne vascular diseases of many solanaceous crops such as pepper. This study aimed to identify QTL for bacterial wilt resistance in a 170 F₈ recombinant inbred line (RIL) population obtained from a cross of ‘YCM334’ x ‘Taean’ using genotyping by sequencing (GBS) approach. For pathogen inoculations, R. solanacearum isolate WR-1 was cultured on NB medium at 28℃ for 48 h and a bacterial suspension was adjusted to 1 x 10⁷ to 1 X 10⁸ CFU/mL (A 600 = 0.3 to 0.4). Seedlings for each RIL and parents were inoculated at the 6 to 8 leaf stage using soil-drenching (3 to 5 ml/ plant) inoculation methods with 3 replications. After 10 days post inoculation, each line was evaluated visually for occurrence of bacterial wilt ranging from 1 (most resistant) to 5 (most susceptible). The construction of four 48-plex libraries from the RIL population is ongoing, and until now two GBS libraries (96 individuals) have been sequenced on one lane each of Illumina HiSeq4000. Approximately 98 gigabases of data containing 646,570,104 paired-end reads were obtained, ranged from 2.0 to 13.2 million reads per individual. A total of 8,579 SNPs were detected between the parents, of which 1,749 SNPs were also detected in the RIL population, and 1,430 of the polymorphic SNPs were high quality suitable for high-density genetic map construction. After GBS analysis for all RILs is completed, several QTL significantly associated with resistance to BW will be presented.