Distinguished Professor University of Florida Gainesville, FL, USA
Gene editing of Bs6 and Bs8 susceptibility loci in tomato for resistance to Xanthomonas spp. Mousami Poudel1, Apekshya Parajuli1, Gerald V. Minsavage1, Samuel F. Hutton2,3, Jeffrey B. Jones1, Anuj Sharma2,3, 1 Department of Plant Pathology, Univ. of Florida, Gainesville, USA 2 Gulf Coast Research and Education Center, Univ. of Florida, Wimauma, USA Bacterial spot caused by several Xanthomonas spp. is a serious disease in tomatoes and peppers. In tomato (Solanum lycopersicum) host resistance is limited, whereas in pepper (Capsicum annuum) besides dominant resistance genes, several recessive resistance genes (i.e., bs5, bs6, bs8) have been identified. These resistances result from mutations in corresponding disease susceptibility genes. Pepper cultivars that carry bs5 provide excellent field resistance to BSP. Recently, the Bs5 homolog in tomato was modified by CRISPR/Cas9-mediated editing. Plants with the resulting mutation had significantly less bacterial spot in greenhouse and field experiments. Two additional susceptibility genes Bs6 and Bs8 also facilitate bacterial multiplication and disease development in pepper. We are developing bacterial spot-resistant tomato plants by knocking out homologs of Bs6 and Bs8. We identified three Bs6 homologs of and one Bs8 homolog in tomato, and designed CRISPR/Cas9 constructs targeting these genes for mutagenesis. Following tomato transformation, we recovered multiple T0 plants with mutations in all four targeted genes. Preliminary assays on the mutant T1 lines indicate reduced bacterial growth, supporting involvement of one or more of these genes in susceptibility. We will continue to focus on validating resistance across multiple generations under greenhouse and field conditions. The anticipated outcome of this work is the development of durable, bacterial spot-resistant tomato varieties.
