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Research Project: Mining Collections of Wild Germplasm and Novel Defense Regulators for Enhanced Plant Defenses

Location: Plant Gene Expression Center

Title: Solanum pimpinellifolium exhibits complex genetic resistance to Pseudomonas syringae pv. tomato

Author
item HASSAN, JANA - University Of California Berkeley
item DIPLOCK, NATHAN - University Of California Berkeley
item CHAU-LY, ILEA - University Of California Berkeley
item CALMA, JAMIE - University Of California Berkeley
item BOVILLE, ELIZABETH - University Of California Berkeley
item YEE, STEVEN - University Of California Berkeley
item HARRIS, TAYLOR - University Of California Berkeley
item Lewis, Jennifer

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2024
Publication Date: 10/23/2024
Citation: Hassan, J.A., Diplock, N., Chau-Ly, I.J., Calma, J., Boville, E., Yee, S., Harris, T.M., Lewis, J.D. 2024. Solanum pimpinellifolium exhibits complex genetic resistance to Pseudomonas syringae pv. tomato. Frontiers in Plant Science. 15. Article 1416078. https://doi.org/10.3389/fpls.2024.1416078.
DOI: https://doi.org/10.3389/fpls.2024.1416078

Interpretive Summary: Crop productivity and yield are substantially reduced by plant diseases. Genetic sources of resistance have been effective in reducing crop losses, however over time, pathogens can evolve to overcome resistance. Wild relatives of crop plants have extraordinary genetic diversity, that can be mined as natural sources of resistance to common pathogens. We previously developed a rapid screen to identify wild tomato lines with resistance to the bacterial pathogen Pseudomonas syringae, which causes bacterial speck. Here, we examined multiple genetic populations of wild tomato to identify genes associated with resistance to P. syringae. This work provides new tools for plant breeders to help protect plants from disease.

Technical Abstract: Pseudomonas syringae pv. tomato (Pst) is the causal agent of bacterial speck disease in tomatoes. The Pto/Prf gene cluster from Solanum pimpinellifolium was introgressed into several modern tomato cultivars and provided protection against Pst race 0 strains for many decades. However, virulent Pst race 1 strains that evade Pto-mediated immunity now predominate in tomato-growing regions worldwide. Here we report the identification of resistance to a Pst race 1 strain (Pst19) in the wild tomato accession S. pimpinellifolium LA1589 (hereafter LA1589), using our rapid high-throughput seedling screen. LA1589 supports less bacterial growth than cultivars, and does not exhibit a hypersensitive response to Pst19. We tested an existing set of 87 Inbred Backcross Lines (IBLs) derived from a cross between susceptible Solanum lycopersicum E-6203 and Solanum pimpinellifolium LA1589 for resistance to Pst19. Using single-marker analysis, we identified three genomic regions associated with resistance. Bacterial growth assays on IBLs confirmed that these regions contribute to resistance in planta. We also mapped candidate genes associated with resistance in a cross between the Solanum lycopersicum var. lycopersicum cultivar Heinz BG-1706 and S. pimpinellifolium LA1589. By comparing candidates from the two mapping approaches, we were able to identify 3 QTL and 5 candidate genes in LA1589 for a role in resistance to Pst19. This work will assist in molecular marker-assisted breeding to protect tomato from bacterial speck disease.