Evaluation of Pepper (Capsicum spp.) Germplasm Collection for Bacterial Wilt (Ralstonia solanacearum) Resistance

Abstract

This study was conducted to identify resistant pepper accessions against the destructive disease bacterial wilt (BW) caused by Ralstonia solanacearum. A total of 338 pepper (Capsicum species) germplasms collected from different countries and deposited in the National Agrobiodiversity Genebank, Rural Development Administration (RDA), Republic of Korea, were evaluated. The evaluated accessions comprise samples from five distinct species: Capsicum annuum (213), Capsicum baccatum (47), Capsicum chinense (45), Capsicum frutescens (31), and Capsicum chacoense (2). Disease severity scores were recorded over four consecutive weeks and showed an increase in severity from initial inoculation to the end of the evaluation period. A strong correlation was observed between week 1 and 2, as well as between week 3 and 4. Ten resistant pepper accessions were identified. All selected accessions consistently exhibited low disease scores ranging from 0 to 1 throughout the observation period. These accessions belong to C. chinense (2), C. annuum (6), C. chacoense (1), and C. frutescens (1). Accessions such as IT236738 (C. chinense) and IT283498 (C. chinense) were demonstrated to have high resistance, showing no symptoms over all four weeks. Other accessions belonging to C. annuum (IT247232 and IT236340) and C. chacoense (IT158713) maintained a disease score of 0 (no symptoms) for the first three consecutive weeks; however, they developed symptoms with a score of 1 in the fourth week. Other important characteristics of the resistant materials were evaluated, including carotenoids and fruit characteristics. These accessions have important traits beyond resistance to the destructive pepper disease. They will serve as promising resources for breeding resistant pepper varieties against BW to enhance productivity.