Minimal versus Intensive: How the Pruning Intensity Affects Occurrence of Grapevine Leaf Stripe Disease, Wood Integrity, and the Mycobiome in Grapevine Trunks

Abstract

Previous works on grapevine-trunk diseases indicate that minimal or non-pruning of the grapevine under certain circumstances can significantly reduce the risk of symptom expression. Nevertheless, knowledge of the mechanisms behind these observations are limited. Therefore, it was the aim of this study to investigate in more detail the effect of pruning intensity on the grapevine trunk by means of trunk integrity and the fungal community in the wood tissue. Two German vineyards partially trained in vertical-shoot position and semi-minimally pruned hedges were chosen for this survey due to the accessibility of multi-annual esca-monitoring data. The results revealed that only in one of the two vineyards was the incidence of external esca symptoms significantly reduced over a period of five years (2017–2021) by minimal pruning, which was up to 73.7% compared to intensive pruning. In both vineyards, the trunks of intensively pruned vines not only had more pruning wounds on the trunk (by 86.0% and 72.9%, respectively) than minimally pruned vines, but also exhibited a larger (by 19.3% and 14.7%, respectively) circumference of the trunk head. In addition, the percentage of white rot and necrosis in the trunks of esca-positive and esca-negative vines was analyzed and compared between the two pruning intensities; hereby, significant differences were only found for esca-negative ‘Dornfelder’ vines, in which the proportion of necrosis was higher for intensively pruned vines (23.0%) than for minimally pruned vines (11.5%). The fungal communities of the differently pruned vine trunks were mainly dominated by four genera, which are also associated with GTDs: Diplodia, Eutypa, Fomitiporia and Phaeomoniella. All in all, the fungal diversity and community composition did not differ between minimally and intensively pruned, esca-positive vines.

Metagenomic Assessment Unravels Fungal Microbiota Associated to Grapevine Trunk Diseases

“…Ascorbate-Glutathione cycle was considered likely to be involved in grapevine susceptibility to fungi associated with the Esca complex [89]. Other hypotheses can contribute for the appearance of leaf symptoms, such as the disturbance of sap flow to the leaves on given xylem pathways altered by fungi, which is described as 'hydraulic dysfunction' [85,90,91], and annual infections by some fungi through pruning or green wounds [23,92]; however, more research is required to develop this hypothesis and to unravel the processes underlying colonization by these fungi [93].…”

“…It is important to consider that several factors can shape the grapevine microbiome and increase/decrease the susceptibility to GTDs, such as seasonality, climatic conditions, surrounding flora, cultural practices, plant genotype, plant age, and presence of pathogens, rootstock, and cultivar [48,50,85,[92][93][94][95][96]. In addition, biotic and abiotic stresses might also be playing an important role in the expression of GTDs symptoms [97].…”

Fungal trunk diseases of fruit trees in Europe: pathogens, spread and future directions

“…Among Diatrypaceae, Eutypa lata has been commonly associated with FTD in Europe. This fungus was found on walnut, quince, grapevine, pistachio, almond, plum, cherry, blueberry, and olive, in the Czech Republic, France, Germany, Italy, and Spain (Prodorutti et al, 2008;Laveau et al, 2009;Luque et al, 2009;Tosi and Natalini 2009;Wenneker et al, 2011;Gramaje et al, 2012;Gierl and Fischer, 2017;Baránek et al, 2018;Aiello et al, 2019;Bien and Damm 2020;Eichmeier et al, 2020;Guarnaccia et al, 2020;López-Moral et al, 2020b;Kraus et al, 2022). Other Diatrypaceae are less frequently associated with FTD in Europe; Eutypella citricola, Eu.…”

“…Several basidiomycetous fungi have been recorded as involved in FTD. Fomitiporia mediterranea is the predominant species in Europe, especially in vineyards, where it causes white rot in grapevine trunks (Rumbos and Rumbou 2001; Laveau et al, 2009;Luque et al, 2009;Akgül et al, 2015;Baránek et al, 2018;Moretti et al, 2021;Kraus et al, 2022). In addition, this fungus was also associated with decline symptoms on olive, kiwifruit, citrus, almond and pear (Elena et al, 2006;Carlucci et al, 2013;Markakis et al, 2017;Olmo et al, 2017).…”

“…spur or cane pruning), can cause more frequent external FTD symptoms than minimal pruning schemes (Lecomte et al, 2018(Lecomte et al, , 2022Kraus et al, 2019). It was also assumed that intensive pruning causes more and larger pruning wounds on grapevine trunks, leading to increased infections by wood degrading fungi, and consequent interruption of host vascular systems and increased symptoms (Travadon et al, 2016;Kraus et al, 2022).…”