Host Range of an Iranian Isolate of Watermelon Chlorotic Stunt Virus as Determined by Whitefly‐mediated Inoculation and Agroinfection, and its Geographical Distribution

Virus like symptoms appeared on most watermelon plants grown at different locations in southern provinces of Iran. The symptoms included chlorotic patches on leaves, vein yellowing and stunting of watermelon plants. The causal agent of watermelon chlorotic stunt disease was transmitted to healthy watermelon, jimsonweed and bean by the whitefly Bemisia tabaci, but not by sap inoculation. Coat protein and nucleic acid of Watermelon chlorotic stunt virus (WmCSV) were detected in infected plants using a dot‐immunobinding assay (DIBA) and squash‐blot hybridization, respectively. The data obtained confirmed that watermelon chlorotic stunt disease in Iran is caused by WmCSV. Agroinoculation of some plant species by the cloned genomic components (DNA‐A and DNA‐B) of a non‐sap‐transmissible Iranian isolate of WmCSV (WmCSV‐Ir) has been demonstrated. Host range studies using agroinoculation indicated that most plant species in the Cucurbitaceae and some species of the Solanaceae are susceptible to WmCSV‐Ir. Infection of agroinoculated plants was confirmed by DIBA and polymerase chain reaction. The virus from agroinfected plants was transmissible by the whitefly Bemisia tabaci. Results obtained from a limited survey during 1997–2000 indicated the presence of WmCSV‐Ir in some watermelon‐growing provinces of southern but not in northern, central, and north‐eastern provinces of Iran. WmCSV has apparently not yet spread to these regions.