Response of endophytic Biscogniauxia mediterranea to variation in leaf water potential of Quercus cerris

Abstract

Endophytic behaviour of Biscogniauxia mediterranea, the causal agent of charcoal disease of oak, was studied over two growing seasons on Quercus cerris in a forest in central Italy. Isolation of the fungus from asymptomatic tissues varied with tissue type, period of sampling and year. Presence of the fungus in asymptomatic plants was significantly higher in fall, compared with that in spring and summer. However, a significant effect of tissue water content on the presence of B. mediterranea was recognized. The results suggest that proliferation of B. mediterranea is favoured during the endophytic phase by a decrease in host water potential.

Climate change and oak growth decline: Dendroecology and stand productivity of a Turkey oak (Quercus cerris L.) old stored coppice in Central Italy

“…Another recent study on Pinus brutia indicated that, as moisture availability decreased, the highest correlations of tree growth with rainfall were obtained for progressively longer integration periods (from 1-2 y in moist periods to 5-6 y during the actual severe drought), suggesting increasing dependency on deep soil water (Sarris et al, 2007). Endophytic attacks may therefore be favored by reduced formation of latewood and increased cavitation, allowing fungi to reach the cambium (Vannini et al, 2009). Climatic conditions that alternate from greatly favorable to unfavorable, as was the case from pre-to post-1997, have also been proposed as the trigger of forest growth decline in dense stands that experience high competition levels (e.g.…”

Latent infection of Biscogniauxia nummularia in Fagus sylvatica: a possible bioindicator of beech health conditions

“…The amount of fungal DNA was significantly higher during the vegetative season (summer) in both sampled forests. From an ecological point of view, B. nummularia behaves in a similar way to B. mediterranea, which proliferates in asymptomatic tissues of Q. cerris during dry growing seasons (Vannini et al 2009). …”

“…The ability of latent pathogens to quickly adapt to new environmental conditions suggests that these organisms could be used as bioindicators of forest health ( Vannini et al 2009, Romeralo et al 2012), in that: (i) their presence can be easily detected; (ii) they are sufficiently sensitive to provide an early warning of change; (iii) iForest 9: 49-54 …”

“…ballota subjected to water stress, inducing necrosis and canker formation and accelerating tree decline and death (Desprez-Loustau et al 2006, Jurc & Ogris 2006, Capretti & Battisti 2007. Water stress favors the proliferation of the fungus in the endophytic phase; the pathogenic ability of B. mediterranea induces cankers and wood decay (Vannini & Scarascia Mugnozza 1991, Collado et al 1999, Vannini et al 2009). Similarly, Bassett & Fenn (1984) showed that asymptomatic seedlings of Quercus alba L. and Q. velutina Lam.…”

“…In prolonged summer drought, B. nummularia takes advantage of the altered host physiology, invades host tissue and causes elongated blackish bark lesions on trunk and branches, known as strip-cankers, and wood decay in mature trees (Hendry et al 1998, Nugent et al 2005. In the related species B. mediterranea (Vannini et al 2009), outbreak of disease on oaks is likely to follow an increase in endophytic colonization. Therefore, monitoring of the endophytic stage of these fungi may provide an indication of droughtinduced stress conditions of the host (Desprez-Loustau et al 2006), i.e., the water deficit that can predispose the plant to disease (Boyer 1995, Schoeneweiss 1975.…”