Consequences of environmental stress on oak: predisposition to pathogens

Wargo, PM

doi:10.1051/forest:19960218

Cited by 118 publications

(101 citation statements)

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“…These fungi live in dead parts or as latent endophytes of living trees and water stress is often only a revealer of their presence, by triggering host susceptibility and/or releasing pathogen quiescence. The ubiquitous nature of these parasites in natural forests, and their role as "ecosystem roguers and scavengers", by killing weakened trees and decaying dead trees, has been highlighted by Wargo [210]. However, this view, together with the naming of pathogens as non-aggressive /facultative /secondary /opportunistic may be somewhat misleading about the potential damage associated with these parasites, especially in managed forests.…”

Section: Discussionmentioning

confidence: 96%

“…It is well established that carbohydrate and protein metabolisms are very sensitive to changes in plant water status. Changes in tree chemistry may then provide compounds that stimulate metabolism and growth of pathogens or decrease toxic or inhibitory contents [210]. For example, glucose, which increases in stressed trees, stimulates growth of Armillaria and enables it to grow in the presence of inhibitory phenols [210].…”

Section: Interaction Effects Through Host Predisposition To Disease Bmentioning

confidence: 99%

“…The role of pathogens as predisposing or triggering agents of decline diseases has also been recognised, especially powdery mildew and Phytophthora spp. in oak declines ( [57,210], cf. case study).…”

Section: Interaction Effects: Drought and Infection Acting As Multiplmentioning

confidence: 99%

“…Changes in tree chemistry may then provide compounds that stimulate metabolism and growth of pathogens or decrease toxic or inhibitory contents [210]. For example, glucose, which increases in stressed trees, stimulates growth of Armillaria and enables it to grow in the presence of inhibitory phenols [210]. Popoola and Fox [162] also demonstrated that levels of carbohydrates, fatty acids and amino-acids were altered in stressed Lawson cypress plants as compared to controls, favouring increased growth of Armillaria mellea and A. gallica on root extracts.…”

Section: Interaction Effects Through Host Predisposition To Disease Bmentioning

confidence: 99%

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Interactive effects of drought and pathogens in forest trees

et al. 2006

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-This review synthesizes the available knowledge on drought-disease interactions in forest trees with a focus on (1) evidence and patterns of drought-disease interactions, (2) current understanding of processes and mechanisms, and (3) three well documented cases studies. The first part is based on the analysis of a database of slightly more than one hundred studies, obtained by keyword searches combining drought, diseases or pathogens, and forest trees. A large majority of published studies referred to a positive association between drought and disease, i.e. disease favoured by drought or drought and disease acting synergistically on tree health status, with a predominance of canker/dieback diseases, caused by pathogens like Botryosphaeria, Sphaeropsis, Cytospora and Biscognauxia (Hypoxylon). The type of disease-related variables (incidence vs. severity) and the intensity and timing of water stress were shown to be significant factors affecting the drought-infection interaction. Interactions with other abiotic stresses and species-specific and genetic effects, related to host or pathogen, have also been reported. Direct effects of drought on pathogens are generally negative, although most fungal pathogens exhibit an important plasticity and can grow at water potentials well below the minimum for growth of their host plants. Studies on indirect effects of drought on pathogens through other community interactions are still relatively scarce. Positive drought-infection effects can mostly be explained by indirect effects of drought on host physiology. The predisposition and the multiple stress hypotheses are presented, as well as recent developments in the study of the molecular basis of abiotic and biotic stress, and their interactions. Sphaeropsis sapinea on pines, Biscognauxia mediterranea on oaks and root pathogens in declines associated with drought provide illustrative examples, treated as case studies, of pathogens of current significance associated with drought. The conclusion highlights some knowledge gaps, e.g. the role of latent parasites and the shift to a pathogenic stage, or the genetics of some fungal groups. The need for prevention of pathogen dispersal, especially crucial in the case of latent pathogens, is emphasized. drought / water stress / pathogenic fungi / predisposition / forest trees Résumé -Interactions entre sécheresse et agents pathogènes chez les arbres forestiers. Cette revue synthétise les connaissances actuelles sur les interactions entre sécheresse et maladies chez les arbres forestiers, avec trois grandes parties : (1) description des types d'interaction ; (2) connaissances acquises sur les mécanismes impliqués ; (3) trois études de cas bien étudiées. La première partie est basée sur l'analyse d'une base de données d'une centaine d'études, sélectionnées par recherche sur mots clés. La plupart de ces études se rapportent à des maladies favorisées par la sécheresse ou à un effet synergique entre sécheresse et maladie sur l'état sanitaire des arbres, avec une prédominance de m...

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Section: Discussionmentioning

confidence: 96%

Section: Interaction Effects Through Host Predisposition To Disease Bmentioning

confidence: 99%

Section: Interaction Effects: Drought and Infection Acting As Multiplmentioning

confidence: 99%

Section: Interaction Effects Through Host Predisposition To Disease Bmentioning

confidence: 99%

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Interactive effects of drought and pathogens in forest trees

et al. 2006

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“…photosynthetic CO 2 uptake). This can cause severe structural anomalies which could lead to the elimination of this tree species (Wargo 1996;Thomas et al 2002). On the other hand, oak species are known to show morphological and physiological adaptations that enable them to delay the impact of unfavourable factors (e.g.…”

Section: Introductionmentioning

confidence: 99%

The anatomical traits of trunk wood and their relevance to oak (Quercus robur L.) vitality

Tulik

2014

Eur J Forest Res

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Oaks' decline in vitality is attributed to a complex process that involves interactions of several factors leading to increased trees' mortality. This study investigates the structure of trunk wood of oaks with reference to its physiological role in hydraulic conductivity. On the basis of the crown condition, the oaks were classified into three health groups: healthy trees, declining trees and dead trees. Anatomical traits of wood, such as annual ring width, vessel density, vessel diameter of earlywood and theoretical hydraulic conductivity, were measured and calculated. The narrowest annual rings formed by the cambium were observed in dead oaks. These trees were also characterized by the smallest diameter of earlywood vessels, not only in the period of occurrence of dieback symptoms, but also during their whole life. It is suggested that the formation of narrow annual rings and earlywood vessels of small diameter increases susceptibility of a tree to decay. A reduced vessel diameter implies changes in hydraulic conductivity of oak trunks and thus impairs the water transport, which affects the health of trees. The process of oak decline is considered to have characteristics of natural selection and leads to the elimination of the weakest trees.

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