First report of Tomato leaf curl New Delhi virus in Türkiye

Abstract

A leaf curl disease has been observed frequently in greenhouses where cucumber (Cucumis sativus), melon (Cucumis melo) and squash (Cucurbita pepo) are produced in Antalya since 2019. The infected plants showed symptoms including apical leaf curl, vein swelling, severely stunted, wrinkled leaves, fruit shape and texture disorder and a conspicuous mosaic pattern (Figure 1-5). These symptoms are similar to those caused by Tomato leaf curl New Delhi virus (ToLCNDV), an important member of the genus Begomovirus, family Geminiviridae. ToLCNDV is transmitted by Bemisia tabaci in a persistent circulative manner, causing serious damage to a wide variety of plant species, especially in the Solanaceae and Cucurbitaceae families (Briddon, 2015). ToLCNDV was first identified on solanaceous crops in India (Padidam et al., 1995) but the virus is recognised as an emerging threat worldwide due to the severity of the disease and its increasing prevalence. Outbreaks have recently occurred in countries in Africa, Asia and Europe (European and Mediterranean Plant Protection Organization, 2023). Samples were collected from eight adjoined greenhouses in Antalya, four growing cucumber, two melon and two squash. Three leaf samples and one fruit sample were collected individually from a diseased plant in each of the greenhouses, that is 32 samples in total. Total nucleic acid was extracted from the leaf and fruit samples and analysed by PCR with specific ToLCNDV primers (ToA1-F and ToA1-R) which amplify a 504 bp fragment of viral DNA-A (Saez et al., 2016). The following conditions were used for PCR: 95°C for 5 min; 35 cycles of 30 s at 95°C, 45 s at 55°C and 45 s at 72°C, followed by a final 72°C extension step for 10 min. Sequences were obtained from samples from each of the eight plants and were found to be identical (GenBank Accession No. MZ458535). BLAST analysis showed that there was 99% identity with a ToLCNDV isolate (MH475397). Antalya is a major area of greenhouse and seed production in Türkiye and the Mediterranean basin. ToLCNDV and other plant viruses are serious threats to solanaceous and cucurbit crops grown in the region since these crops may be infected through mechanical contact, seeds and insects (Kil et al., 2020). Quarantine remains the most effective way to prevent and control such viral infections. Diseased plants in the affected greenhouses were destroyed and the houses sanitised using solarization and disinfectant. Further surveys were done in 2020 and 2021 in the affected and neighbouring greenhouses and potentially virus-infected plants (~ 84 cucurbit samples) were tested by PCR as described above. No ToLCDV infection was found indicating that the virus had been eradicated. To our knowledge, this is the first report of ToLCNDV in Türkiye.