P-478 - Emergence and spread of Begomovirus coheni associated with tomato yellow leaf curl disease: impact on sustainable production of tomatoes in the USA

Tomato yellow leaf curl disease (TYLCD) is primarily caused by the whitefly-transmitted tomato yellow leaf curl virus (TYLCV; Begomovirus coheni). This disease severely impacts tomato (Solanum lycopersicum L.) production worldwide. In addition to TYLCV, a complex association with the tomato chlorosis virus has been identified in tomato cultivars in southern Georgia, USA. Although several commercial tomatoes have been developed with intermediate resistance gene(s) against TYLCV-IL (Israel) isolate, we observed high disease severity in seven extensively grown tomato cultivars under natural conditions. Three full-length sequences and 26 intergenic regions of B. coheni isolated from symptomatic tomato plants were generated from samples collected in Grady, Colquitt, and Tift counties, in Georgia, USA. A phylodynamic analysis of B. coheni associated with TYLCD indicates a polyphyletic clade closely related to European and Mediterranean isolates. Furthermore, the analysis of TYLCV isolates identified from tomatoes revealed a basal diversification into two major clades. Agrobacterium-mediated infectivity assay of TYLCV-GA (Georgia) isolate showed severe symptoms in tomato cultivars after 30 days post-inoculation. Additionally, the genetic parameters of TYLCV-GA indicated purifying selection or recent population expansion of tomato-associated viruses in the US. Our study demonstrated that a shift in TYLCV populations in Georgia leads to TYLCD in commercial tomato cultivars. Future research is needed to develop resistance against emerging TYLCV-GA isolate.