Low susceptibility of grapevine infected by GLRaV-3 to late Plasmopara viticola infections: Towards understanding the phenomenon

Plant–pathogen interactions occurring in the vineyards often comprise the coexistence of a large number of microorganisms with different virulence. The aim of the work was to investigate the interactions between the grapevine leafroll associated virus 3 in Vitis vinifera and late downy mildew infection in the field. After veraison virus occurrence reduced some photosynthetic parameters while it increased the level of some stilbene compounds like piceids and resveratrol. Moreover, an increased expression of some defence-related genes was detected. Some degree of defence activated against leafroll virus could partially explain the observed reduced susceptibility to late Plasmopara viticola attacks in virus-infected grapevine plants.

► GLRaV-3 infected grapevine plants showed reduced symptoms of late downy mildew in field.
► Leaf photosynthetic parameters slightly decreased in virus-infected plants.
► Both stilbene amount and defence-related gene expression increased in virus-infected plants.
► Some virus-induced alterations may partly explain grapevine reduced susceptibility to fungal infection.