Distribution and diversity of viruses affecting cucurbit production in New South Wales, Australia

Cucurbits are an important crop grown across peri-urban, coastal and inland regions of New South Wales, Australia. Viral infection is a persistent issue across cucurbit commodities, different production methods and production regions. In this study, 34 cucurbit growing properties across five production regions of New South Wales were surveyed and sampled repeatedly from 2018 to 2021. Samples were tested for the presence of known endemic viruses using both serological and molecular diagnostic methods. Viral pathogens were detected on 22 of the 34 properties sampled, and in 44% of samples tested. Annual disease incidence ranged from 0 to 90%, typically increasing towards the end of the summer growing season. Papaya ringspot virus, watermelon mosaic virus, and cucumber mosaic virus, were identified as the most frequently detected viruses. Melon necrotic spot virus and beet pseudo yellows virus were detected at low rates. Cases of mixed infections of papaya ringspot virus and watermelon mosaic virus were also detected in some samples. Furthermore, cucumber green mottle mosaic virus, a “notifiable disease”, was detected for the first time in New South Wales. A newly described virus, watermelon crinkle leaf associated virus-1, was also detected using next- generation sequencing technology. The latter two virus records represent a geographic range expansion and first report for Australia respectively.