ASHS 2025 Conference

Tomato (Solanum lycopersicum) growers report that foliar diseases are their biggest production challenge. The tomato organic management and improvement (TOMI) project was launched in 2014 with support from the NIFA-OREI program to address this challenge. We have applied a transdisciplinary approach, integrating studies aimed at 1) increasing biocontrol efficacy, 2) understanding mechanisms controlling induced systemic resistance (ISR), and 3) developing new varieties using a participatory breeding approach. In our biocontrol studies, we learned that combining products with different modes of action was not effective, however, if applied early and often, some biocontrol agents can reduce disease across diverse locations and years. Potting media and composts containing residues with high carbon to nitrogen ratios can increase survival and efficacy of a soil-applied biocontrol agent. In our ISR studies, we learned that not all tomato genotypes are responsive to this form of disease control. The most responsive are wild relatives (Solanum pimpinellifolium), which release distinct compounds from their roots to signal and support soil microbes with biocontrol capabilities. ISR responsiveness is associated with upregulation of brassinosteroid and phenylpropanoid pathways, and grafting appears to promote ISR activity. Identifying genetic markers will improve selection for this trait. Finally in our breeding program, we learned that engaging growers in the selection process aids in the development of new varieties with the most desirable set of traits. We made significant gains in advancing populations and some advanced lines are being considered for release by seed companies, though resistance in many populations is not effective in all ecoregions. Regionally-focused breeding programs are likely to be more effective in developing varieties best adapted to local environmental conditions and disease complexes. We are continuing to work closely with growers to advance these efforts. More information about our project and resources for growers can be found on our website: https://eorganic.info/tomi.