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Molecular markers for pathogen resistance in tomato
Tomato ( Solanum lycopersicum) is one of the most popular vegetables worldwide. Tomato production is seriously constrained by plant diseases in major cultivation areas. The most important of these plant diseases are root-knot ( Meloidogyne spp.), late blight ( Phytophthora infestans), fusarium wilt ( Fusarium oxysporum), verticillium wilt ( Verticillium spp.) , leaf mold ( Fulvia fulva), bacterial wilt ( Ralstonia solanacearum), bacterial spot ( Xanthomonas campestris)), tomato yellow leaf curl virus (TYLCV), tomato spotted wilt virus (TSWV) and tomato mosaic virus (ToMV). Agrochemical application is an efficient way for controlling pathogens today, however, using resistant cultivar is the best solution to avoid environmental pollution and keep the balanced, sustainable growth and human health. Traditionally, tomato breeders develop disease-resistant cultivars through the introgression of resistant genes by back-cross-breeding following pathogen infection selection. Recently, marker-assisted selection (MAS) for resistance to pathogens has been used to identify resistant and susceptible genotypes, resulting in improving the breeding efficiency, accelerating the breeding progress and saving the cost of breeding resistant cultivars.
Nowadays, a team composed of researchers from TSIPS (Taiwan Seed Improvement and Propagation Station) and AVRDC (The World Vegetable Center) successfully developed advanced Sequenced-Characterized- Amplified-Region (SCAR) markers linked to resistant genes of TYLCV, TSWV, ToMV, fusarium wilt, and root-knot nematode in tomato. These improved markers can be applied easily and reliably for tomato breeders to screen the target progeny from segregating population in the early stage of breeding progress. This will accelerate the breeding progress of new varieties with stacked resistant genes. These technologies have been transferred to some domestic tomato seed companies for the development of resistant varieties.
Fig.1. How to screen disease-resistant plants from thousands of individual plants in the field for breeders?
Fig.2. Molecular markers assay would not be affected by environmental condition and used to identify resistant genotypes and predict diseases severity at early stages.