Host Crop Influence on the Virulence of Tomato Spotted Wilt Virus Isolates in Southeast Georgia, USA

Globally, tomato spotted wilt virus (TSWV) is a serious pest causing tomato spotted wilt disease (TSWD) on a wide range of plant hosts. Integrated pest management (IPM) strategies are crucial for mitigating TSWD incidence in horticultural and row crops. To assess the impact of various IPM approaches on TSWV, we studied four different TSWV isolates collected from peanut (TSWV peanut), tobacco (TSWV tobacco), and tomato (TSWV tomato-1 and tomato-2) crops commonly grown in southeast Georgia, USA. All four isolates were phenotypically assessed based on disease incidence (DI), disease severity (DS), and serially passaged in Nicotiana tabacum cv NC196. In addition, viral genomic molecules were measured in the newly emerged leaves of the inoculated tobacco plants. Nucleocapsid (NP), non-structural movement (NSm), and non-structural silencing suppressor (NSs) gene sequences were analyzed from passages zero, two, and four. Our findings suggested 80-100% of DI in mechanically inoculated plants by all the isolates at 21 days post inoculation (DPI). Based on the expression of symptoms in inoculated plants, high DS was observed in plants inoculated with the TSWV peanut isolate. The difference between viral titer at 7, 14, and 21 DPI was not observed for any of the isolates. On successive passages, virulence decreased for all the isolates (except TSWV tomato-2 isolate). Our study indicated the difference in virulence between TSWV isolates from peanut, tobacco, and tomato crops on N. tabacum.