Research Project: Impact of Grapevine Leafroll-associated Virus 3 Genetic Variants and Emerging Viruses on Wine Grape Quality in the Pacific Northwest

Location: Horticultural Crops Production and Genetic Improvement Research Unit

Project Number: 2072-21000-057-036-G
Project Type: Grant

Start Date: May 1, 2023
End Date: Oct 31, 2026

Objective:
1. Characterization of the prevalence and distribution of the strains and genetic variants of Grapevine leafroll-associated virus 3 (GLRaV-3) and other emerging viruses in vineyards. 2. Development of specific tools for detection and differentiation of emerging grapevine viruses and GLRaV-3 strains. 3. Elucidation of the specific effects of grapevine viruses and individual GLRaV-3 strains on wine grape quality under PNW conditions.

Approach:
Many viruses infect grapevines in the Pacific Northwest (PNW), often in mixed infections, and quite often represented by multiple genetic variants. For instance, GLRaV-3 is well known to exist as a complex of genetic variants or strains separated into at least eleven phylogroups based on the genome sequences. We hypothesize that the effects of these viruses and their genetic variants on wine grape berry yield and quality may be different and would like to address this hypothesis. To characterize the virus population present in the vineyards, genomes of these viruses and their strains will be differentially detected using RT-PCR or High-Throughput Sequencing (HTS) in infected plants exhibiting symptoms of grapevine leafroll disease (GLD) in Idaho. RNA will be extracted from those symptomatic field samples and subjected to RT-PCR using strain-specific primers, or, for HTS, depleted of ribosomal RNAs, and, after generating a library of cDNAs, submitted to the HTS technology. Bioinformatic analyses will identify viruses and their genetic variants with a primary focus on GLRaV-3. Individual plants in the same vineyards infected with different viruses and their genetic variants will be identified during the first year and permanently tagged for berry quality studies. In years 2 and 3, vine yield and clusters will be collected from healthy and infected plants. A subsample of berries will be analyzed for anthocyanins (color compounds), proanthocyanidins (color and texture compounds), sugars (sweetness), and organic acids (tartness) in year 3 (after both growing seasons’ samples are collected). This will allow to compare the effects of individual genetic variants of GLRaV-3 on the yield and quality of berries.