High-throughput identification of resistance to Pseudomonas syringae pv. tomato in tomato using seedling flood assay

Authors: HASSAN, JANA - University Of California; CHAU-LY, ILEA - University Of California; Lewis, Jennifer

Submitted to: Journal of Visualized Experiments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2019
Publication Date: 3/10/2020
Citation: Hassan, J.A., Chau-Ly, I.J., Lewis, J.D. 2020. High-throughput identification of resistance to Pseudomonas syringae pv. tomato in tomato using seedling flood assay. Journal of Visualized Experiments. 157.Article e60805. https://doi.org/10.3791/60805.
DOI: https://doi.org/10.3791/60805

Interpretive Summary: Pseudomonas syringae causes substantial disease under appropriate environmental conditions. We developed a rapid high-throughput seedling-based screen to identify wild species of tomato with resistance to P. syringae. Common cultivars of tomato lack resistance to the strains of P. syringae that are now observed in agricultural settings. The seedling-based screen allows for reduced plant growth time and large sample sizes, which expedites the search for resistance to bacteria. We provide a detailed protocol for conducting the seedling resistance assay, to facilitate use of the screen in multiple laboratories. New sources of resistance can be introduced into cultivars, which will improve the anti-microbial resistance of tomato with better genetic resources for plant breeders and growers, and will provide consumers with enhanced food security.

Technical Abstract: Tomato is an agronomically important crop, that can be infected by Pseudomonas syringae, a Gram-negative bacterium, resulting in bacterial speck. The tomato-P. syringae pv. tomato pathosystem is widely used to dissect the genetic basis of plant innate responses and disease resistance. While disease was successfully managed for many decades through the introduction of the Pto/Prf gene cluster from Solanum pimpinellifolium into cultivated tomato, race 1 strains of P. syringae have evolved to overcome resistance conferred by the Pto/Prf gene cluster and predominantly occur worldwide. Wild tomato species are important reservoirs of natural diversity in pathogen recognition, as they evolved in diverse environments with different pathogen pressures. In typical screens for disease resistance in wild tomato, adult plants are used, which can limit the number of plants that can be screened due to their extended growth time and required growth space. We developed a method to screen 10-day-old tomato seedlings for resistance, which minimizes plant growth time and growth chamber space, allows a rapid turnover of plants, and allows large sample sizes to be tested. Seedling outcomes of survival or death can be treated as discrete phenotypes or on a resistance scale defined by amount of new growth in surviving seedlings after flooding. This method has been optimized to screen 10-day old tomato seedlings for resistance to two P. syringae strains, and can easily be adapted to other P. syringae strains