Grapevine trunk disease symptomology data to identify individual grapevines as candidates for the “disease escape” phenotype

Abstract

Grapevine trunk diseases (GTDs), caused by a complex of fungal pathogens, pose significant challenges to viticulture in New Zealand and globally. There are few effective controls for these fungal pathogens, with most management aimed at preventing new infections via wound treatments. Recent research has demonstrated that mature vines thriving in areas of high disease can contain distinctive trunk microbiomes. These vines have been termed “disease escape” vines. Further research has shown that reintroduction of microbial taxa recovered from such vines into young grapevine canes can confer some resistance to the causal agents of GTD. However, selection of “disease escape” vines is difficult and labour intensive, requiring the application of clear criteria such as vine age, and lack of symptoms. In New Zealand, manual surveys of vines in commercial vineyards have been undertaken over time to understand the effectiveness of current, limited, GTD management methods. We investigated if symptom expression over time coupled with relative chlorophyll measurements in a 34-year-old commercial block of Sauvignon blanc vines could be used to detect putative “disease escape” vines. The vines were surveyed six times between 2018 and 2024. The trunk material of individual vines, with and without GTD symptoms (short shoots, cankers, half-head, re-worked, replacements, gaps and dead vines), in areas mapped with high disease pressure were biopsied. Vines from other areas of the same block without symptoms and surrounded by other asymptomatic vines were also collected. DNA metabarcoding of the ribosomal internal transcribed spacer 1 (ITS1) and 16S ribosomal RNA gene was applied to the trunk samples. The identification of distinctive microbiomes in putative “disease escape” vines, and their correlation with the symptomology mapping, spatial proximity of “healthy” vines and chlorophyll measurements is presented.