Quantitative Assessment of Grapevine Wood Colonization by the Dieback Fungus Eutypa lata.

Cédric Moisy,Timothée Flutre,Gilles Berger,Jean-Pierre Péros,Loïc Le Cunff

doi:10.3390/jof3020021

Abstract

Eutypa lata is a fungal pathogen causing severe dieback in vineyards worldwide. This fungus colonizes vines through pruning wounds, eventually causing a brown sectorial necrosis in wood as well as stunted vegetative growth. Several years may pass between infection and the expression of external symptoms, hindering the rapid evaluation of both grapevine cultivars susceptibility and E. lata variation in aggressiveness. We aimed to develop a rapid quantitative method for the assessment of wood colonization after inoculation of cuttings in controlled conditions. We used several grape cultivars varying in susceptibility in the vineyard and fungal isolates with different levels of aggressiveness to monitor wood colonization during a maximum period of 2 months. Re-isolation allowed demonstration of the effects of both cultivars and fungal isolates on the rate of wood colonization. We also developed a real-time PCR method that was efficient in measuring fungal biomass, which was found to be correlated with isolate aggressiveness based on foliar symptom severity. The real-time PCR approach appears to be a useful technology to evaluate grapevine susceptibility to E. lata, and could be adapted to other pathogens associated with grapevine trunk diseases.

Highlights

Grapevine trunk diseases (GTD: Eutypa, Esca disease, and Botryosphaeria dieback) are severe diseases affecting grapevines (Vitis spp.) worldwide [1,2,3,4,5,6,7]
E. lata can be concealed by other fungi present in the wood chips and growing faster on potato-dextrose agar (PDA) medium, preventing its development and identification
The rest of the samples were either considered as “uncontaminated” when no E. lata was observed or “colonized by E. lata” if the fungus was identified after sub-culture on PDA medium

Summary

Introduction

Grapevine trunk diseases (GTD: Eutypa, Esca disease, and Botryosphaeria dieback) are severe diseases affecting grapevines (Vitis spp.) worldwide [1,2,3,4,5,6,7] They dramatically shorten vineyard longevity and compromise their sustainability because the causal pathogens attack long-lasting organs, inducing vine death on the shorter or longer term. The disease is caused by the ascomycete Eutypa lata [8], a random-mating species displaying high genetic diversity [9] This fungus is a pathogen for more than 80 other species, including apricot, almond, cherry, apple, olive, peach, pear, ornamental species, and walnut [10,11,12,13]. Symptoms in grapevine include shorter stem internodes, dwarfed and necrotized leaves, some brown and hard sectorial necrosis inside woody parts, and cankers on arms and trunk [13]

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