Evaluating Quantitative Trait Locus Resistance in Tomato to Multiple Xanthomonas spp

Area of Science:

• Plant Pathology
• Genetics
• Horticulture

Background:

• Bacterial spot, caused by four Xanthomonas species, significantly impacts tomato production.
• Pesticide control has proven ineffective, necessitating genetic resistance strategies.
• Previous research identified three quantitative trait loci (QTL) on chromosome 11 (QTL-11A, QTL-11B, QTL-11C) conferring resistance.

Purpose of the Study:

• To evaluate the effectiveness of different chromosome 11 QTL introgressions for bacterial spot resistance.
• To determine which QTL provides the greatest resistance against multiple Xanthomonas species.
• To assess the efficacy of combining QTL resistance with a major gene (Rx-4/Xv3).

Main Methods:

• Development of near-isogenic lines (NILs) through marker-assisted backcrossing.
• Introduction of resistance sources (QTL-11A, QTL-11B, QTL-11C, Rx-4/Xv3) into a susceptible tomato parent (OH88119).
• Field trials evaluating NILs inoculated with X. perforans, X. euvesicatoria, and X. gardneri over three years (2016-2018).

Main Results:

• QTL-11C and QTL-11A, particularly when combined with Rx-4/Xv3, demonstrated effective genetic resistance against multiple Xanthomonas species.
• Evidence suggests additive to dominant genetic action for the evaluated QTL introgressions.
• NILs provided a robust platform for assessing genetic resistance components.

Conclusions:

• Specific QTL introgressions from wild tomatoes, especially QTL-11C and combined QTL-11A with Rx-4/Xv3, are valuable for breeding bacterial spot-resistant tomato varieties.
• Genetic resistance strategies are crucial for sustainable management of bacterial spot disease.
• Further research into the genetic mechanisms underlying resistance is warranted.