Deciphering the Niches of Colonisation of Vitis vinifera L. by the Esca-Associated Fungus Phaeoacremonium aleophilum Using a gfp Marked Strain and Cutting Systems

Abstract

IntroductionEsca disease has become a major threat for viticulture. Phaeoacremonium aleophilum is considered a pioneer of the esca complex pathosystem, but its colonisation behaviour inside plants remains poorly investigated.Material and MethodsIn this study, P. aleophilum::gfp7 colonisation was assessed six and twelve weeks post-inoculation in two different types of tissues: in the node and the internode of one year-old rooted cuttings of Cabernet Sauvignon. These processes of colonisation were compared with the colonisation by the wild-type strain using a non-specific lectin probe Alexa Fluor 488-WGA.ResultsData showed that six weeks post-inoculation of the internode, the fungus had colonised the inoculation point, the bark and xylem fibres. Bark, pith and xylem fibres were strongly colonised by the fungus twelve weeks post-inoculation and it can progress up to 8 mm from the point of inoculation using pith, bark and fibres. P. aleophilum was additionally detected in the lumen of xylem vessels in which tyloses blocked its progression. Different plant responses in specific tissues were additionally visualised. Inoculation of nodes led to restricted colonisation of P. aleophilum and this colonisation was associated with a plant response six weeks post-inoculation. The fungus was however detected in xylem vessels, bark and inside the pith twelve weeks post-inoculation.ConclusionsThese results demonstrate that P. aleophilum colonisation can vary according to the type of tissues and the type of spread using pith, bark and fibres. Woody tissues can respond to the injury and to the presence of this fungus, and xylem fibres play a key role in the early colonisation of the internode by P. aleophilum before the fungus can colonise xylem vessels.

Variations in Early Response of Grapevine Wood Depending on Wound and Inoculation Combinations with Phaeoacremonium aleophilum and Phaeomoniella chlamydospora

“…Grapevine material was collected in vineyards and conditioned as described in Pierron et al (2015a) . One-year-old canes of V. vinifera L. cv.…”

“…In fact, the accumulation of suberin in pruning wounds correlates with their susceptibility to infection by Eutypa lata ( Munkvold and Marois, 1995 ) and may participate in trunk defense more than does the accumulation of lignin ( Pouzoulet et al, 2014 ). Discoloration of wood following the annual growth ring ( Mugnai et al, 1999 ) and the occlusion of xylem vessels ( Mori et al, 2001 ; Pierron et al, 2015a ) has also been characterized. More recently, by comparing wounded and inoculated cuttings with wounded and non-inoculated cuttings, Czemmel et al (2015) revealed that, compared with the latter, the former has a lower starch content 2 months post-inoculation with Neofusicoccum parvum .…”

“…Early colonization by P. aleophilum 6 and 12 weeks post-inoculation revealed that xylem fibers were colonized prior to xylem vessels and that the plant response varies according to plant tissue. This response was due only to wounding in the internode, but comparison with mock-inoculated plants in the node indicates that the response is particular to the presence of the pathogen ( Pierron et al, 2015a ). Inoculation with P. chlamydospora affects wound healing, which also suggests that grapevine wood may perceive the presence of the pathogen or its effectors ( Bruno and Sparapano, 2006 ; Santos et al, 2006 ).…”

“…Although, trunk defenses have been described as non-specific and as depending only on wounding damage ( Blanchette and Biggs, 1992 ), some recent tissue-scale results from grapevines ( Pouzoulet et al, 2013a ; Czemmel et al, 2015 ; Pierron et al, 2015a ) and cellular-scale results from non-woody material ( Lima and Dias, 2009 ; Luini et al, 2010 ; Bénard-Gellon et al, 2014 ) suggest that a certain level of plant perception contributes to the plant-defense reaction. The altered wound healing in Cabernet Sauvignon cuttings upon inoculation with P. chlamydospora ( Pouzoulet et al, 2013a ) suggests that wood tissues in V. vinifera L perceive this pathogen.…”

Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

“…In addition, diseased plants display an impaired water transport (caused by xylem dysfunction), which in turn leads to a considerable decline of leaf gas exchange and water use efficiency traits (Edwards et al, 2007;Pouzoulet et al, 2014). It was recently demonstrated that the impaired water transport can be caused, at least in part, by P. minimum and P. chlamydospora both growing into the xylem vessel lumens, limiting water transport and inducing the deposition of tyloses as plant defence response (Landi et al, 2012;Pierron et al, 2015).…”