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

Abstract

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.

Further Molecular Diagnosis Determines Lack of Evidence for Real Seed Transmission of Tomato Leaf Curl New Delhi Virus in Cucurbits

“…Some other ToLCNDV-ES modes of transmission have been described as cultivardependent [63]. For instance, the whitefly transmission of the Spanish strains from zucchini to watermelon and wild cucurbit species has been reported as inefficient, even at high inoculum pressure [12,64]. Additionally, the Spanish isolate of this viral species can be mechanically transmitted to cucurbits but at different rates, depending on the assayed host species [23].…”

The Role of Satellites in the Evolution of Begomoviruses

“…However, with the increase in irrigation and a gradual rise in global temperatures, the population dynamics of B. tabaci gradually changed, and they remained active throughout the year, resulting in the emergence of diseases caused by begomoviruses in crops that were previously free from such infections [ 1 ]. The global-warming-led increase in the B. tabaci population and its spread have also resulted in the emergence of begomovirus-induced diseases in parts of Europe that were not affected by such diseases earlier [ 14 ].…”

First report of Cucurbit Chlorotic Yellows Virus (CCYV) and Tomato Leaf Curl New Delhi Virus (ToLCNDV) in Algeria and lack of evidence for seed transmission of ToLCNDV in melon and pumpkin.

“…Some other ToLCNDV-ES modes of transmission have been described as cultivar-dependent (Janssen et al, 2022). For instance, the whitefly transmission of the Spanish strains from zucchini crops to plants of watermelon and wild cucurbit species has been reported as inefficient, even under high inoculum pressure (Farina et al, 2023;. Additionally, the Spanish isolate of this viral species resulted mechanically transmitted to cucurbits, but with different rates of success depending on the assayed species .…”