Stacking Robust Resistance to Septoria Leaf Spot from Wild Germplasm Accessions into the Cultivated Tomato

Project Overview

LNE21-427R
Project Type: Research Only
Funds awarded in 2021: $198,977.00
Projected End Date: 02/29/2024
Grant Recipient: West Virginia University
Region: Northeast
State: West Virginia
Project Leader:
Dr. Vagner Benedito
West Virginia University

Commodities

  • Vegetables: tomatoes

Practices

  • Crop Production: plant breeding and genetics
  • Pest Management: genetic resistance

    Proposal abstract:

    The long-term goal of our research program is to use natural genetic variation in tomato to increase sustainability of crop management systems by providing breeding tools for resistance to key pests and diseases of tomato. Septoria leaf spot (SLS) of tomato is becoming an increasingly important fungal disease in the Northeast and many neighboring states in the eastern seaboard of the US where hot and humid weather prevails during the growing season in most years. This aggressive foliar disease can devastate tomato crops, to which varieties with effective tolerance are not available. A recently released variety (‘Iron Lady’) was claimed to be tolerant to SLS, but our trials showed that it does not offer sufficient protection against the predominant pathogen strain in mid-Appalachia. There is a critical need of deconvoluting the genetics behind this trait and to develop resistant varieties via introgression of robust SLS resistance from wild species into commercial varieties of tomato. This research project, therefore, aims to respond to our farmers’ needs by identifying strong sources of resistance against SLS in the tomato germplasm, introgressing it into a cultivated variety, and creating breeding tools. The specific aims of this project are: 1) to introgress the novel trait ‘SLS resistance’ from wild accessions into a popular heirloom tomato variety (‘Cherokee’) by creating interspecific hybrids via embryo rescue; 2) to identify the genetic locus responsible for SLS resistance (through a mapping-by-sequencing genomic approach); and 3) to develop bona fide CAPS markers for breeding. Backcrossing will be carried out in greenhouse conditions. Selection will occur in both, greenhouse as well as yearly in the field for performance evaluation at the WVU Organic Farm with the most advanced inbred line available. As preliminary work, we have circumvented the major bottlenecks of this project (thus, making it a low-risk, high-reward investment) by identifying several sources of genetic tolerance (including complete resistance) to Septoria lycopersici in wild tomato accessions, producing 10 viable hybrids, and we have already started the introgression work into the cultivated tomato by recurrent backcrossing and selection. An advisory panel has been formed with crop specialists and farmers, who will meet virtually with the research team once a year for updates and discussion of the directions and priorities of the project. We have pre-built connections with farmers in WV and neighboring Appalachian regions, who will be actively involved in beta-testing and selecting the finalist genotypes prior to final selection for variety release. The main end-product generated from this research will be a long-term, science-based sustainable solution for management of an increasingly important foliar disease to growers who will adopt this variety. The plant material and molecular markers developed in this project will be made available to farmers, breeders, and researchers.

    Performance targets from proposal:

    As a direct response to farmers’ needs, the research objective is to develop a tomato cultivar that is resistant to Septoria Leaf Spot (SLS) by introgressing a novel natural resistance source we identified in wild tomatoes. No effective resistance against SLS is available in any tomato cultivar. We produced several F1 hybrids via embryo rescue. We will also map the resistance locus, identify the gene, and develop molecular markers for breeding. Our research will deliver a breeding toolkit to tomato breeders interested in incorporating SLS resistance in their cultivars, and the resistant materials will be available to farmers and breeders.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.