Bacteria associated with wood tissues of Esca‐diseased grapevines: functional diversity and synergy with Fomitiporia mediterranea to degrade wood components

Abstract

Fungi are considered to cause grapevine trunk diseases such as esca that result in wood degradation. For instance, the basidiomycete Fomitiporia mediterranea (Fmed) is overabundant in white rot, a key type of wood-necrosis associated with esca. However, many bacteria colonize the grapevine wood too, including the white rot. In this study, we hypothesized that bacteria colonizing grapevine wood interact, possibly synergistically, with Fmed and enhance the fungal ability to degrade wood. We isolated 237 bacterial strains from esca-affected grapevine wood. Most of them belonged to the families Xanthomonadaceae and Pseudomonadaceae. Some bacterial strains that degrade grapevine-wood components such as cellulose and hemicellulose did not inhibit Fmed growth in vitro. We proved that the fungal ability to degrade wood can be strongly influenced by bacteria inhabiting the wood. This was shown with a cellulolytic and xylanolytic strain of the Paenibacillus genus, which displays synergistic interaction with Fmed by enhancing the degradation of wood structures. Genome analysis of this Paenibacillus strain revealed several gene clusters such as those involved in the expression of carbohydrate-active enzymes, xylose utilization and vitamin metabolism. In addition, certain other genetic characteristics of the strain allow it to thrive as an endophyte in grapevine and influence the wood degradation by Fmed. This suggests that there might exist a synergistic interaction between the fungus Fmed and the bacterial strain mentioned above, enhancing grapevine wood degradation. Further step would be to point out its occurrence in mature grapevines to promote esca disease development.

Fomitiporia mediterranea M. Fisch., the historical Esca agent: a comprehensive review on the main grapevine wood rot agent in Europe

“…Synergism between Fmed and bacteria such as Paenibacillus spp. for grapevine wood component degradation has also been confirmed (Haidar et al, 2021).…”

The microbiota of the grapevine holobiont: A key component of plant health

“…It seems that the onset of symptoms cannot be correlated with the mere presence of the fungus responsible for the decline inside the wood or with its greater or lesser abundance [38] (this is also the case for other fungal diseases such as hoja de malvón [126] ) . A recent study even supposes that Fomitiporia mediterranea virulence (one of the pathogenic fungi responsible for esca) and in particular its capacity to degrade wood is due to an interaction with certain bacteria present in the wood [163] . Nevertheless, significant differences in endophytic bacterial composition have been found between the wood of symptomatic grapevines and the wood of asymptomatic grapevines, whether they were necrotic or not: important differences for Bacillales - more abundant in asymptomatic plant - , Xanthomonadales, Rhizobiales, Enterobacteriales and unidentified taxa - more abundant in symptomatic grapevines - [162] .…”

Grapevine trunk diseases of cold-hardy varieties grown in Northern Midwest vineyards coincide with canker fungi and winter injury

“…Grapevine trunk diseases (GTDs) make up a disease complex most often associated with several wood-inhabiting fungal species [ 1 ] and more recently possibly some bacterial species [ 2 ]. Sub-groups of these diseases are frequently categorized by symptomology and or taxonomic designation of causal fungal agents.…”