Expanded host range of grapevine virus A in vineyard ecosystems

Abstract

Grapevine virus A(GVA), a member of the genus Vitivirus (family Betaflexiviridae), is an economically important pathogen associated with grapevine wood diseases and significant yield losses. While both cultivated and wild Vitis species are recognised as natural hosts, the role of alternative hosts in virus epidemiology remains poorly understood. This study investigated the ability of the vine mealybug (Planococcus ficus) to transmit GVA from infected grapevines to non-grapevine plant species commonly found in Croatian vineyards.

Transmission experiments conducted under greenhouse conditions over three consecutive years demonstrated successful vector-mediated infection of several herbaceous hosts. Serological and molecular assays (DAS-ELISA, end-point RT-PCR, real-time RT-PCR), complemented by electron microscopy and sequencing in selected cases, confirmed GVA infection in velvetleaf (Abutilon theophrasti), redroot pigweed (Amaranthus retroflexus), field poppy (Papaver rhoeas), nettle-leaved goosefoot (Chenopodium murale), and the previously known host Nicotiana benthamiana. Infection rates varied among species and experimental years.

Infected plants exhibited a range of symptoms including leaf reddening, chlorotic spotting, vein clearing, foliar deformation, reduced lateral shoot growth, and dwarfism, although infections in A. theophrasti remained asymptomatic. Attempts to transmit GVA back from infected herbaceous hosts to virus-free grapevines were unsuccessful under the conditions tested.

The identification of new alternative hosts suggests that weeds in vineyards may act as reservoirs of GVA inoculum and contribute to virus persistence and spread. These findings expand the known host range of GVA and provide new insights into its epidemiology, highlighting the importance of considering non-Vitis species in disease management strategies.