Grapevine Shiraz disease-associated viruses lead to yield losses by altering transcription of genes

Abstract

Context and Purpose of Study. Grapevine Shiraz disease (SD), which is associated with Grapevine Virus A (GVA), is one of the highly destructive diseases affecting Australian and South African vineyards. However, virtually nothing is known about the transcriptional modifications in grapevine phloem tissues induced by SD as well as its impact on vine physiology, yield and fruit composition. We therefore conducted an evaluation of SD on mature Shiraz grapevines in the warm climate region of Riverland, South Australia.

Materials and methods. Physiological parameters, including vine water status, leaf gas exchange and PSII chlorophyll fluorescence, as well as yield components and fruit composition of SD-infected Vitis vinifera L. cv. Shiraz vines grown in a commercial vineyard in the Riverland region of South Australia were assessed over two growing seasons, 2020/21 and 2021/22. Viruses present in symptomatic SD-affected and asymptomatic vines were investigated using serological (ELISA) and molecular tests (PCR and Illumina next generation sequencing (RNA-seq)). Phylogenetic and differential transcript expression analyses were done on the RNA-seq data.

Results. SD did not alter plant water status over the growing season, however significantly decreased canopy size, leaf gas exchange, PSII chlorophyll fluorescence, and yield. Differential gene expression analysis revealed significantly higher expression of genes associated with systemic acquired resistance (SAR) and downregulation of defence- and photosynthesis-related genes in phloem tissues of SD vines. This is the first report of the physiological and transcriptomic effects of SD on grapevines.