Anju Pandey, PhD Candidate
Graduate Research Assistant
North Carolina State University
Raleigh, North Carolina, United States
Rajan Paudel (he/him/his)
Graduate Research Assistant
North Carolina State University
Raleigh, North Carolina, United States
Tika Adhikari (he/him/his)
North Carolina State University
Raleigh, North Carolina, United States
Bode A. Olukolu
Assistant Professor
University of Tennessee
Knoxville, Tennessee, United States
Reza Shekasteband
Research Scholar
North Carolina State University
Mills River, North Carolina, United States
Ralph A. Dean
Professor
North Carolina State University
RALEIGH, North Carolina, United States
Frank J. Louws
Professor
North Carolina State University
RALEIGH, North Carolina, United States
Dilip R. Panthee
Associate Professor
North Carolina State University
Mills River, North Carolina, United States
Septoria leaf spot (SLS), caused by Septoria lycopersici, poses a major threat to tomato production in the eastern United States and Canada. To address this issue, there is an urgent need to discover genes associated with SLS resistance to incorporate into new tomato cultivars. Additional work is needed to discover and advance reliable sources of genetic resistance to this disease. This study evaluated a panel of 220 advanced tomato lines from the North Carolina State University tomato breeding program, and wild relatives from the USDA Agricultural Research Service in Geneva, NY, and the Tomato Genetics Resource Center at the University of California, Davis, CA. The plants were inoculated with locally isolated S. lycopersici strains and evaluated weekly for three consecutive weeks. The study was conducted twice to assess SLS resistance at the seedling stage in the greenhouse. Among the genotypes evaluated, 17 exhibited resistance, 46-displayed moderate resistance, and 157 were found to be susceptible. Genotyping was performed using OmeSeq-qRRS, which generated 46,466 high-quality SNP markers for genome-wide association studies. A linear mixed model in the R package GWASpoly, incorporating a kinship matrix calculated using the VanRaden method, identified four significant SNPs associated with defense-related genes linked to SLS resistance. This study enhances our understanding of the genetic basis of underlying SLS resistance and offers valuable molecular markers that can facilitate the development of disease-resistant tomato cultivars through molecular breeding.