Synergistic Interaction Between Southern Tomato Virus and Tomato Spotted Wilt Virus During Tomato Infection

Abstract

Synergistic infections by different viruses exacerbate symptoms, broaden host ranges, and cause severe economic losses, becoming a critical factor in viral disease epidemics. Mixed-infection by Amalgavirus lycopersici (commonly known as southern tomato virus, STV) and Orthotospovirus tomatomaculae (commonly known as tomato spotted wilt virus, TSWV) results in leaf necrosis, fruit hardening, and severe yield loss in tomatoes. However, the mechanisms by which their synergistic infections aggravate tomato diseases remain unclear. From 2020 to 2023, the incidence of STV and TSWV was monitored by RT-PCR in a total of 572 tomato samples. The annual incidence of STV was 29.0%, 31.5%, 31.1%, and 45.2% in 2020, 2021, 2022, and 2023, respectively, while that of TSWV was 23.3%, 18.9%, 22.5% and 16.1%, respectively. Shoot tip detoxification technology was applied to cultivate virus-free seedlings of Ninghuang-1, and 80% of virus-free plants survived in large-scale cultivation experiments. Mixed-infection markedly increased viral RNA and TSWV N protein expression levels, accompanied by severe damage to chloroplasts, mitochondria, and other cellular structures. Putative STV virions were observed. This study provides a theoretical foundation and has practical implications for green prevention and control of viral diseases in the field.