Wood necrosis in esca-affected vines: types, relationships and possible links with foliar symptom expression

Abstract

<p style="text-align: justify;"><strong>Aims</strong>: Esca disease of grapevine is characterised by foliar symptoms associated with the development of various internal wood necroses. The aims of the present study are to determine the type and the quantity of necroses in the various woody compartments of vines, the relationships between them and the links between necroses and severity of foliar symptoms.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Symptomatic and asymptomatic vines cv Cabernet- Sauvignon were cross-sectioned to quantify the different types of internal necrosis in the scions (cordons, heads, and trunks) and rootstocks. Five necrosis « variables » were accounted for: central necrosis, sectorial necrosis, mixed necrosis, white rot, altered perimeter and in addition to the variable healing cone. In the scion, for all types of necrosis variables, a significant correlation between compartments was found. Vines with acute foliar form of esca had very advanced peripheral tissue degradations in the xylem and cambial zones. Chronic foliar expression of esca was associated with quantity of internal necroses higher than those obtained for asymptomatic vines. A logistic model indicated that white rot in the cordons was the best predictor for the chronic form of esca.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Necroses formed a continuum within the plant. The scion is like a single unit with a volume of necroses useful to determine the health status of vines.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: A quantitative analysis of vine internal necroses would open up new possibilities for esca-epidemic approaches.</p>

Grapevine pruning systems and cultivars influence the diversity of wood-colonizing fungi

“…The point of sampling these different wood types was not to demonstrate a relationship between wood necrosis and the presence of trunk pathogens. Indeed, trunk pathogens and other wood-colonizing fungi are reported from both apparently healthy wood, e.g., Maher et al (2012) and Bruez et al (2014) and discolored/necrotic wood, e.g., Luque et al (2009) and Kuntzmann et al (2010b). Instead, we chose this sampling scheme to focus on xylem of different ages, which might have become infected at different times in the vine's lifespan, and also because other wood-colonizing fungi examined in forest and shade trees (namely basidiomycetes) are often categorized based on their ability to colonize heartwood versus sapwood.…”

Fungal community associated with grapevine wood lesions in Lebanon

“…Collections were made in 2005 and 2007 after the expression of typical esca leaf symptoms (Lecomte et al, 2012). Isolations were performed in wood lesions classified into at least three main categories as described by Larignon (2004) or Maher et al (2012). To our knowledge, this is the first study using this classification method before microbial examination.…”

“…D. seriata and N. parvum were the most often isolated species in the current study. Botryosphaeriaceae fungi were also frequently found from mixed necrosis typical of esca (Larignon, 2004;Maher et al, 2012). As recently mentioned by White et al (2011), the role of these latter species -which were largely predominant in the wood of esca-affected vines and which were mainly considered as saprobe on grapevine in the past (Gubler et al, 2005;Larignon and Dubos, 1997;Úrbez-Torres, 2011) -in the development of esca is still unclear and needs to be further studied.…”

“…The expression of esca symptoms on the leaves is commonly associated with the development of different fungal pathogens in grapevine wood (Arnaud and Arnaud, 1931;Chiarappa, 1959;Dubos, 2002;Mugnai et al, 1999). Cross sections of the trunk of diseased vines generally reveal a variety of lesions and/or decay types (Larignon and Dubos, 1997;Larignon, 2004;Maher et al, 2012). The wood of older vines usually shows a white to yellow soft rot, from which basidiomycetes like Fomitiporia spp.…”

Evaluating the Suitability of Hyper- and Multispectral Imaging to Detect Foliar Symptoms of the Grapevine Trunk Disease Esca in Vineyards

“…Although grapevine cultivars differ in their sensitivity to the disease complex, no cultivated or wild grapevine species is known to be resistant [3,4]. Typical wood symptoms are several forms of discolorations and necroses, vascular infections, and in older vines also white rot [5]. Since the Esca complex is a slow perennial disease, external symptoms do usually not become apparent until several years after infection [6].…”