Can vessel dimension explain tolerance toward fungal vascular wilt diseases in woody plants? Lessons from Dutch elm disease and esca disease in grapevine

Abstract

This review illuminates key findings in our understanding of grapevine xylem resistance to fungal vascular wilt diseases. Grapevine (Vitis spp.) vascular diseases such as esca, botryosphaeria dieback, and eutypa dieback, are caused by a set of taxonomically unrelated ascomycete fungi. Fungal colonization of the vascular system leads to a decline of the plant host because of a loss of the xylem function and subsequent decrease in hydraulic conductivity. Fungal vascular pathogens use different colonization strategies to invade and kill their host. Vitis vinifera cultivars display different levels of tolerance toward vascular diseases caused by fungi, but the plant defense mechanisms underlying those observations have not been completely elucidated. In this review, we establish a parallel between two vascular diseases, grapevine esca disease and Dutch elm disease, and argue that the former should be viewed as a vascular wilt disease. Plant genotypes exhibit differences in xylem morphology and resistance to fungal pathogens causing vascular wilt diseases. We provide evidence that the susceptibility of three commercial V. vinifera cultivars to esca disease is correlated to large vessel diameter. Additionally, we explore how xylem morphological traits related to water transport are influenced by abiotic factors, and how these might impact host tolerance of vascular wilt fungi. Finally, we explore the utility of this concept for predicting which V. vinifera cultivars are most vulnerable of fungal vascular wilt diseases and propose new strategies for disease management.

Water deficit effects on grapevine woody tissue pigmentations

“…Thus, they indicate specific tissue answers to the drought stress. In particular, it is possible to hypothesize an accumulation of phenolic derivatives in the rootstock xylem, maybe also related to vessels occlusions and suberin deposition: all this behaviour is a typical plant adaptation to stressed conditions (Pouzoulet et al 2013). Considering Cabernet Sauvignon stems, the absorption decrease could be explained by the accumulation of sclereids which could screen the brown pigment reflectance detection (Rajaei et al 2013).…”

The Parenchyma of Secondary Xylem and Its Critical Role in Tree Defense against Fungal Decay in Relation to the CODIT Model

“…Dutch elm disease is an exception in that it is defined as a vascular wilt and does not cause decay, a pertinent point when the original interpretation of CODIT (compartmentalisation of ‘decay’ in trees) does not typically include vascular wilt diseases. However, Shigo et al (1980) along with Shigo and Tippett (1981) have used CODIT to describe the nature of tree responses to Dutch elm disease, and the concept has supported various wilt diseases more widely since (Pouzoulet et al, 2014). …”

“…It is speculated that RAP indirectly prevents the spread of decay by keeping air-filled conduits isolated (Rayner and Boddy, 1988; Schenk et al, 2008), by refilling of conduits (Brodersen et al, 2010; Knipfer et al, 2016), or by keeping water-flow continuous through a buffering effect via capacitance (Meinzer et al, 2009; Jupa et al, 2016). Fungi flourish when oxygen is available, enabling them to use air-filled conduits as a kind of ‘highway’ for their growth and, inevitably, decay spread within the xylem (Baum and Schwarze, 2002; Yadeta and Thomma, 2013; Pouzoulet et al, 2014). Other roles of parenchyma that are directly or indirectly related to tree defense include: (1) storage of NSCs, while acting as a fuel for new growth along with cell metabolism and repair, NSCs also play a key role against drought stress (Rosas et al, 2013; O’Brien et al, 2014, 2015), and are pivotal against damage (including pathogens) as the carbon is used to build polyphenolic compounds and suberin, which are toxic to microbes (Hillis, 1977; Shain, 1979, 1995; Magel et al, 1994); (2) transition of sapwood into heartwood, where the living cells of RAP die and undergo chemical changes in the process that impregnate the heartwood with microbe resistant toxic extractives (Schwarze et al, 2000c; Spicer, 2005; Spicer and Holbrook, 2007), while the contact cells exude tyloses or gels (sometimes called plugs or gums) into the vessels, particularly by RP (Chattaway, 1949); and (3) the lignification of the secondary cell wall of RP, which, while providing biomechanical support, also imparts with a greater resistance to microbial penetration.…”

Efecto de las alcamidas como inductores de tolerancia al estrés biótico en tomate

“…El efecto de H. longipes y el C+ sobre el número de vasos de xilema posiblemente tenga una función positiva para la planta disminuyendo la vulnerabilidad del xilema frente a la cavitación causada por el ataque de patógenos que afectan el sistema vascular (Sobrado, 2007;Pouzoulet et al, 2014).…”

“…The effect of H. longipes and C+ on the number of xylem vessels may have a positive role for the plant reducing xylem vulnerability against cavitation caused by the attack of pathogens that affect the vascular system (Sobrado, 2007;Pouzoulet et al, 2014). …”