Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f.sp. lycopersici (Fol), threatens tomato crops globally. Fol causes substantial yield losses in susceptible plants and is persistent once established in fields, making gene-based resistance a high-priority for growers. Historically, Fol strains isolated in the Midwest United States have been predominantly race 1, and I-based resistance has been widely deployed and effective. However, there have been increasing numbers of samples sent to diagnostic clinics in the Midwest with Fusarium wilt symptoms, suggesting a potential shift in Fol race prevalence and the need to deploy additional resistances. The aim of our project is to introgress the I3 resistance gene, effective against race 3 Fol, into Midwest-suited processing tomato lines. I3 was originally identified in Solanum pennellii, a wild relative of cultivated tomato (Solanum lycopersicum), and a minimal introgression which reduced linkage drag was developed and introduced into Fresh-Market tomatoes by the University of Florida. We developed backcross families with the I3 gene using the Florida minimal introgression and recurrent parents from the Ohio processing tomato breeding program. Lines were selected for advancement based on I3 genotyping, background genome selection using unlinked single nucleotide polymorphisms (SNPs), and phenotyping of relevant yield and quality characteristics. Our analysis found no significant differences in yield and quality traits between the backcross selections and their recurrent parents, indicating the rapid conversion of parents through this strategy. We are currently combining the I3 and I2 resistance genes through further crossing and will ultimately develop high-performing processing tomato lines suited to Midwest growing conditions that are resistant to all three Fol races.
