Tomato Leaf Curl New Delhi Virus Spain Strain Is Not Transmitted by Trialeurodes vaporariorum and Is Inefficiently Transmitted by Bemisia tabaci Mediterranean between Zucchini and the Wild Cucurbit Ecballium elaterium

Simple Summary Begomoviruses constitute a successful group of emerging plant viruses threatening vegetable, root and fiber crops worldwide that are transmitted in nature by whiteflies of the Bemisia tabaci complex. Tomato leaf curl New Delhi virus is a paradigmatic example of a begomovirus that has recently emerged in Mediterranean countries after movement from its original location in the Indian subcontinent. The Mediterranean isolates of this virus belong to a novel strain, named "Spain strain", which infects zucchini and other cucurbits but is poorly adapted to tomato. This work aimed to clarify some aspects of the whitefly transmission of tomato leaf curl New Delhi virus. It was shown that contrary to a recent study reporting the transmission of an Indian isolate of the virus by the greenhouse whitefly (Trialeurodes vaporariorum), the Mediterranean isolate is not transmitted by this insect. In addition, the most prevalent Bemisia tabaci species, Mediterranean, is not an efficient vector of this begomovirus between zucchini plants and the wild cucurbit Ecballium elaterium. These results suggest that this wild plant, although frequently infected, may not play a relevant role as a reservoir in the epidemiology of the disease caused by tomato leaf curl New Delhi virus Spain strain. Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus (genus Begomovirus, family Geminiviridae) persistently transmitted, as with all other begomoviruses, by whiteflies (Hemiptera: Aleyrodidae) of the Bemisia tabaci cryptic species complex. The virus, originally from the Indian subcontinent, was recently introduced in the Mediterranean basin, where it is currently a major concern for protected and open-field horticulture. The Mediterranean ToLCNDV isolates belong to a novel strain named "Spain strain" (ToLCNDV-ES), which infects zucchini and other cucurbit crops but is poorly adapted to tomato. Recently, it has been reported that another whitefly, Trialeurodes vaporariorum, is able to transmit an isolate of ToLCNDV from India which infects the chayote plant, a cucurbit. The present work aimed to clarify some aspects of whitefly transmission of ToLCNDV-ES. It was shown that T. vaporariorum is not able to transmit ToLCNDV-ES between zucchini plants. In addition, Ecballium elaterium may not act as a relevant reservoir for this virus strain in the Mediterranean basin, as B. tabaci Mediterranean (MED), the most prevalent species of the complex in the region, is not an efficient vector of this begomovirus between cultivated zucchini and wild E. elaterium plants.