Structural modifications induced by Eutypa lata in the xylem of trunk and canes of Vitis vinifera

Abstract

Eutypa dieback, a devastating disease in grapevines, is caused by the fungal pathogen Eutypa lata, a wood-inhabiting fungus. E. lata acts by degrading wood tissues in the colonisation areas, and produces foliar symptoms. These striking symptoms have been attributed to the production of toxic metabolites by the pathogen, the most widely studied being eutypine. The aims of the study were to compare the effects of E. lata on xylem structure at the site of infection and in remote tissues. In healthy Vitis vinifera, the vessel-associated cells (VACs) in the trunk have a protective layer that covers the entire lignified wall and forms a transfer apparatus in pits located at the VAC / vessel interface. This apparatus occurs similarly in VACs in the basal part of canes but is less developed in the apical part. In the presence of E. lata, which is found only in the trunk and the cordons, the VACs initiated a program of secretory activity that led to the enlargement of the transfer apparatus, which is formed by tightly associated fibrils. This secretory activity was followed by VAC death. Furthermore, the hypertrophy of the transfer apparatus spread according to an acropetal gradient in the canes. Treatment with eutypine also induced the development of the transfer apparatus in VACs of basal and apical parts of canes excised from healthy vines. However, this apparatus was formed by loosely packed fibrils in VACs that were not completely damaged. Therefore, metabolites other than eutypine are expected to be involved in the VAC degeneration observed in infected vines.

Early pathogen detection under different water status and the assessment of spray application in vineyards through the use of thermal imagery

“…Furthermore, these authors have shown that P. viticola induces an increase in stomatal aperture in the dark as opposed to the expected stomatal closure. Changes in the semi-permeable properties of plasma membranes are among the first host reactions to fungal infection (Lucas and Dickinson 1998), causing the accumulation of metabolites induced by abnormal phloem transport (Guimaraes and Stotz 2004;Rudelle et al 2005). In the pathogenesis of Pseudoperonosporales cubens such shifts towards strong sinks for nutrients have been reported, causing a massive transfer into the developing sporangia (Cohen et al 1971).…”

Grapevine trunk diseases: complex and still poorly understood

“…1c). The type of wood decay that is caused by E. lata is classified as a soft rot (Rudelle et al. , 2005; Rolshausen et al.…”

“…The degradation of the wood has been characterized by the death of vessel‐associated cells (Rudelle et al. , 2005).…”

The response to stress treatments of potted grapevines inoculated with <i>Eutypa lata</i> and <i>Botryosphaeria lutea</i> fungi associated with trunk disease

“…Thus, it is thought that the experimental design used in the present series of experiments may have contributed to non detection of significant differences between the treatments. Previous research on the effects of plant stress on response to pathogen challenge or disease symptom development suggested that stress (Ferreira et al 1999;Treutter 2005;Desprez-Loustau et al 2006), particularly carbohydrate stress (Rudelle et al 2005), may be important for decreasing vine defence response but also can reduce the ability of the pathogen to invade and establish depending on the timing of the stress. Desprez-Loustau et al (2006) reported that many of the positive drought-disease interactions involved increased severity or impact of the disease rather than increased incidence of infection and so the timing of stress is important.…”

“…However, many of the vines sampled were not expressing any symptoms of trunk diseases even when the pathogens were present. The pathogens of interest have been identified as wound invaders (Mundy & Manning 2010) and stress on the vines at the time of wounding has been reported as one possible factor that could influence vine response to pathogen invasion (Rudelle et al 2005;Desprez-Loustau et al 2006;Petit et al 2006;Mundy & Manning 2011). Carbohydrates are important both to the vine's defence mechanisms against wounding and to the wound invading process of many pathogens (Mundy & Manning 2011).…”