Assessing Tomato Lines with Bwr-6 and Bwr-12 Loci for Resistance to Ralstonia solanacearum Species Complex Phylotypes I and II from North Carolina

Bacterial wilt (BW), caused by members of the Ralstonia solanacearum species complex (RSSC), is a devastating disease affecting many crops, including tomato. Among the management practices implemented to combat BW, developing host resistance is the most effective approach. Therefore, it is crucial to identify sources of resistance within the available tomato germplasm. In this study, we evaluated 10 tomato lines from the World Vegetable Center in Taiwan, each possessing either the Bwr-6 or the Bwr-12 linked marker gene for BW resistance. We used two RSSC strains in our experiments: phylotype I strain NG-RL01 and phylotype II strain K60, both isolated from North Carolina. The two independent experiments were conducted simultaneously in a greenhouse using a split-plot design with six replications. Five-week-old plants were drenched and inoculated in the wounded root zone with a suspension of a 2-day-old bacterial culture. Disease severity was assessed daily using a standard disease rating scale, and the area under the disease progress curve was calculated. The results showed significant differences between the two bacterial strains, the tomato lines, and their interactions. Furthermore, K60 was more aggressive than NG-RL0. Most of the tomato lines were resistant to strain NG-RL01; however, none of the tested lines showed resistance to strain K60. Interestingly, a few plants, specifically AVTO2102, showed some resistance to K60. The findings indicate that the BW resistance-linked markers Bwr-6 and/or Bwr-12 confer considerable resistance to strain NG-RL01 but are ineffective against strain K60, emphasizing the need for research to enhance resistance across different RSSC strains.