Effect of carbohydrate stress and grafting on symptoms in potted grapevines dual inoculated with Seimatosporium sp. and Neofusicoccum parvum

Abstract

Grapevine trunk diseases (GTDs) are a major threat to the viticulture and wine industry, causing yield loss. Botryosphaeria dieback is caused by a number of endophytic latent pathogens, including Neofusicoccum parvum, with plant stress indicated to trigger symptom expression by this pathogen. Further, the interaction between N. parvum and other trunk associated fungi, such as Sematiosporium spp., on disease development is unclear, and the influence of combined biotic and abiotic stress on GTD expression remains unanswered. In the present study, the combined effect of abiotic carbohydrate stress (leaf removal) and biotic stress (dual inoculation of Seimatosporium spp. and N. parvum) on symptom expression in grafted and own-rooted Sauvignon blanc potted vines was investigated. Lesion length and pathogen colonisation distance by re-isolation were assessed after 3 months. For co-inoculation with both Seimatosporium spp. and N. parvum, lesion length and pathogen colonisation distance were longer in own-rooted stressed compared to grafted stressed vines, and own-rooted non-stressed compared to grafted non-stressed vines. Lesion length was longer in co-inoculation (Seimatosporium spp. + N. parvum) versus N. parvum (alone) in stressed own-rooted vines, and longer in co-inoculation (S. lichenicola + N. parvum) versus N. parvum (alone) in grafted non-stressed vines. No lesions developed with Seimatosporium spp. inoculation alone in all treatments (stress and grafting). The movement of Seimatosporium spp. was different between factors. Carbohydrate stress along with dual inoculation of GTD pathogens and trunk associated fungi were shown to influence symptom expression differently in grafted and own-rooted vines.