Two Tomato spotted wilt virus (TSWV) isolates H1 and H2 found in Hippeastrum hybridum plants were characterized based on biological, serological, and molecular properties. Virus isolates showed differences in symptom expression – H1 isolate displayed severe necrotic spots and patterns, whereas mild mosaic symptoms were observed on H2-infected H. hybridum plants. Both TSWV isolates showed comparable reactivity with TSWV-specific antibodies and they induced similar symptoms on herbaceous indicator plants, but some differences between these isolates were detected at the nucleotide sequence level of genomic S and M ssRNAs segment fragments. The nucleotide sequences encoding nucleocapsid (N) and nonstructural (NSs and NSm) proteins showed 98.2%, 97.5%, and 96.5% identity, respectively. Phylogenetic analysis of N and NSs sequences conducted for tested isolates and 31 TSWV isolates included for comparison revealed that H1 and H2 isolates fell into the same cluster and they were grouped together with isolates found previously in different vegetables, ornamentals, and weeds. When NSm ORF was analyzed, the tested isolates formed a separate cluster: H1 isolate showed the highest affinity with TSWV isolates infecting chrysanthemum and pepper plants, whereas H2 isolate was most closely related to other virus isolates found in sweet pepper and tomatoes. These results indicate that both isolates were reassortants between different virus isolates, and represented two novel genetic patterns of TSWV.
