# Does multiple infection of tomato leaf curl New Delhi virus (ToLCNDV) and watermelon mosaic virus (WMV) cause a more severe disease in melon?

Atiwich Patthamapornsirikul, Eric Verdin, Cecile Desbiez

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Atiwich Patthamapornsirikul, Eric Verdin, Cecile Desbiez. Does multiple infection of tomato leaf curl New Delhi virus (ToLCNDV) and watermelon mosaic virus (WMV) cause a more severe disease in melon?. 20. Rencontres de virologie végétale (RVV 2025), Jan 2025, Aussois, France. hal-05147379

HAL Id: hal-05147379

https://hal.inrae.fr/hal-05147379v1

Submitted on 7 Jul 2025

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Variabilité/diversité des virus & épidémiologie

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# Does multiple infection of tomato leaf curl New Delhi virus (ToLCNDV) and watermelon mosaic virus (WMV) cause a more severe disease in melon?

Atiwich Patthamapornsirikul (atiwich.patthamapornsirikul@inrae.fr), Eric Verdin, Cécile Desbiez

Pathologie Végétale, INRAE, Montfavet, France

The emergence of Tomato leaf curl New Delhi virus (ToLCNDV; *Begomovirus solanumdelhiense*) in France and across the Mediterranean can induce complex interactions with other cucurbit-infecting viruses present in the area, leading to varied outcomes in disease severity and viral accumulation. These interactions can present distinct types, including synergism, where viruses mutually enhance each other's effects; asymmetric synergism, where one virus or viral component in a multipartite virus gains disproportionately over the other; and antagonism, where one virus restricts the other's impact. ToLCNDV has previously demonstrated asymmetric synergistic interactions with other begomoviruses and antagonistic relationships with certain tobamoviruses. In France, where ToLCNDV was first detected in 2020, some isolates presented an atypical "recover" phenotype, where symptom severity in susceptible cucurbits decreased in the course of infection. We studied the potential interactions of ToLCNDV with watermelon mosaic virus (WMV; *Potyvirus citrulli*), a prevalent virus in Southern France. A severe Spanish isolate ES13-35 and a French "recover" isolate FR443-1, were co-transmitted with WMV in mixed-sap inoculations on susceptible melon plants. Physical measurements—such as disease index, plant height, and weight—were used to assess disease severity, while viral accumulation was measured using multiplex TaqMan qPCR. Mixed infections produced more severe symptoms than single infections, and the recovery associated to isolate FR443-1 was no more observed, Mixed infection resulted in increased ToLCNDV accumulation without change in WMV accumulation, suggesting an asymmetric synergistic relationship where ToLCNDV gains disproportionately, potentially exacerbating disease impacts on cucurbit crops. This study highlights the need for targeted management strategies to mitigate these complex viral interactions in Mediterranean agriculture.

*Mots clés :* ToLCNDV - WMV - Mixed infection - Virus interactions - Synergism.