Host Crop Influence on the Virulence of Tomato Spotted Wilt Virus Isolates in Georgia, U.S.A

Globally, tomato spotted wilt virus (TSWV) is a serious pest causing tomato spotted wilt disease (TSWD) on a wide range of host plants. Integrated pest management strategies are crucial for mitigating TSWD incidence in horticultural and row crops. To assess the impact of host 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 Georgia, United States. All four isolates were phenotypically assessed based on disease incidence and severity and serially passaged in Nicotiana tabacum 'NC196'. In addition, genomic RNAs of TSWV were measured in the newly emerged leaves of the inoculated tobacco plants. Nucleocapsid, non-structural movement, and non-structural silencing suppressor gene sequences were analyzed from passages zero, two, and four. Our findings showed 80 to 100% disease incidence in mechanically inoculated tobacco plants by the TSWV isolates studied at 21 days postinoculation (DPI). Based on the expression of symptoms in inoculated plants, high disease severity was observed in plants inoculated with the TSWV-peanut isolate. There was no statistical difference in virus copy number in the inoculated plants at 7, 14, and 21 DPI between TSWV isolates. On successive passages, virulence decreased for all the isolates (except TSWV-tomato-2). Our study indicated the difference in virulence between TSWV isolates from peanut, tobacco, and tomato crops on N. tabacum.