2018 ASHS Annual Conference

Tomato spotted wilt virus (TSWV) is an economically damaging pathogen of tomatoes. Typical symptoms of TSWV include wilting or stunning plants and chlorotic or necrotic rings on leaves and fruits. The symptoms can cause yield losses. The precise positioning of TSWV resistance genes on genetic maps is critical for improving the effectiveness of marker-assisted selection (MAS). The objective of this study was to fine map the TSWV resistance gene Sw7 from S. chilense accession LA1938. The fine mapping was initiated by identifying recombination events from F₄ plants using molecular markers. Four different types of co-dominant molecular markers including high resolution DNA melting analysis (HRM) based on single nucleotide polymorphisms (SNPs) were used. The rate of natural thrips-vectored TSWV infection was evaluated in field trials conducted in Florida (2007, 2011, 2012, 2013) and Hawaii (2014). Further, whole genome sequencing (WGS) of two resistant breeding lines, Fla. 8516 and Fla. 8820, and plotting of SNPs and insertions and deletions of DNA segments on tomato chromosomes were conducted to identify the introgression of the wild tomato genome. Together, TSWV resistance gene Sw7 has been fine mapped into 4.0-Mbp interval close to the telomere (within 10% of the chromosome length) on tomato chromosome 12.