Regional influence and cultivar predisposition affect the prevalence of grapevine fungal pathogens in Portuguese vineyards

Grapevine fungal pathogens are responsible for substantial yield losses and increased costs for producers aiming to maintain healthy vineyards, making viticulture less cost-effective in heavily affected regions. Fungi that target the woody organs of the vine can cause severe structural damage and plant death, in syndromes collectively known as grapevine trunk diseases (GTDs). The widespread presence of fungi makes it challenging to predict and control outbreaks. We hypothesize that pathogen diversity and prevalence would vary significantly among cultivars and regions. This study assessed commercial vineyards in nine economically important wine-producing regions of Portugal, identifying 312 grapevines with symptoms. Fungal isolates were recovered from necrotic wood tissue and DNA was extracted. Fragment amplification and sequencing allowed the construction of phylogenetic trees, for relationship clarification between taxa. The most common symptoms were associated with Esca and Botryosphaeria dieback, which aligned with the pathogen isolations. The most isolated pathogens were Phaeomoniella chlamydospora (infected 18.9% of grapevines), Diplodia seriata (27.6%) and Neofusicoccum parvum (15.4%). GTD distribution varied by region, with Botryosphaeria dieback being the most prevalent GTD, followed by Esca. This trend was also seen in specific pathogens, where certain fungi showed high prevalence in one region but not in another; for example, N. parvum, which represented 30% of the fungal isolates from PGI Lisboa, but only 4.4% and 7.4% from PGI Algarve and PDO Alentejo, respectively. Furthermore, grapevine cultivar influenced pathogen colonization; for instance, some pathogens were isolated more frequently from particular cultivars even in regions where their overall prevalence was low (e.g. cv. Trincadeira in PDO Alentejo). These findings provide regional and cultivar insights into the distribution of GTD, contributing information for the effective application of GTD management strategies in commercial vineyards, thus helping producers in the mitigation of the impact of these diseases and avoiding high-risk vineyard management measures.