Grapevine pruning strategy affects trunk disease symptoms, wood pathobiome and mycobiome

Vine training and pruning are cultural strategies that can be deployed to manage grapevine trunk diseases (GTDs). Forty-year-old commercial vineyards in the Cognac region, France, trained to either Guyot-Arcure (severe pruning) or Guyot-Poussard (minimal pruning), were studied to determine how the two systems affected trunk disease symptomatology. Effects of pruning practices on the pathobiome and mycobiome of asymptomatic grapevines were also assessed, using culture- and amplicon-based Illumina sequencing approaches. The hypothesis examined was that severe pruning of Guyot-Arcure increases trunk diseases incidence and severity, and causes higher pathogen load and microbial diversity, compared to Guyot-Poussard. Numbers of symptomatic and asymptomatic vines for the two training systems were recorded over 3 years, including numbers of vines with esca foliar symptoms, and partially unproductive and dead vines. Six asymptomatic vines from each pruning method were selected, and culturing and sequencing data were obtained from 27 samples per vine. Fungi in the Phaeomoniellaceae, Togniniaceae, and Botryosphaeriaceae were the most frequently identified. The data indicated that severe pruning increased risk of pathogen infections, with Phaeomoniella chlamydospora, Phaeoacremonium minimum and Diplodia sp. being the most commonly identified fungi. Greater numbers of dead or dying vines were recorded in the severely pruned vineyard, indicating that this strategy shortens vine longevity. Results also showed that severe pruning increased endophytic microbial diversity, and that the pruning methods influenced mycobiome community composition. This knowledge will improve recommendations to growers for practical and cost-effective ways to manage GTDs.