23 research outputs found
Changes in Ectomycorrhizal Diversity in a Declining Quercus ilex Coastal Forest
Oak decline is generally accepted to be the result of a dynamic interaction between oaks and a mix of
abiotic and biotic causes, within which environmental stresses (drought, salinity, frost, low fertility) may be important
as predisposing factors. As a result of these interactions, trees gradually begin to show symptoms of general
suffering, which below ground consist of functional and anatomical modifications to the rootlets and changes in the
ectomycorrhizal status. The present study was performed in a coastal Quercus ilex forest, where decline symptoms
appeared after heavy land reclamation in the adjoining areas, which caused a rapid lowering of the ground water
level and the underground intrusion of seawater from the neighbouring Adriatic Sea into the forest itself. A forest
survey including examination of rootlet features from asymptomatic and declining trees suggested that drought and
salinity were involved in this decline. The relative frequency of the most recurrent ectomycorrhizal morphotypes
distinguished clearly between asymptomatic, weakly declining and strongly declining trees, suggesting that the
occurrence and distribution of only a limited number of morphotypes can give an indication of the severity of the
decline. Moreover, of all the morphotypes observed only one third were found in all three decline classes, while the
remaining two thirds were gradually replaced by others as the proportion of declining trees increased, where the
number of morphotypes was greater. The hypothesis of an adaptive response of the ectomycorrhizal community to
decline or to the predisposing factors of decline is discussed
Hygrotermic Treatment of Chesnut Logs Infected with Cryphonectria parasitica
Due to the reduced availability of large-sized chestnut logs in Europe, many European timber industries
currently get their supplies from non-European countries, mainly from the Caucasian region, which are often not
immune to chestnut blight. Given the high risk of introducing new virulent strains incompatible with local hypovirulent
ones, the European Union regulation requires that chestnut logs, imported from so-called âthird partyâ nations where
Cryphonectria parasitica is present, reach the European boundaries bark free: this prevents the production of veneers,
which are highly remunerative, but whose first workmanship phases require barked logs. Following a multilevel
investigation, the authors propose a stem-flow protocol that can devitalise the parasite in barked logs while
preserving the commodity characteristics of the wood, through a fast, simple and low-cost treatment, that can be
performed at the European borders whenever C. parasitica is or might be present
Probability of ectomycorrhizal infection in a declining stand of common oak
The study was conducted on 50-55-year-old common oak (Quercus robur L) trees growing in a Ornithogalo pyrenaici-Carpinetum betuli. Four different classes of decline were determined. In each class, in a root sample belonging to ten common oaks, the number of tips with and without mycorrhizal mantle were counted and the probability of finding vital mycorrhizae was determined. The mycorrhizal morphotypes were described and their frequency calculated. The study demonstrated a significant decrease in the proportion of mycorrhizae between healthy and declining plants. Among damaged trees, the increase in decline did not correspond to a decrease in the probability of mycorrhizal infection. There was no correspondance between the probability of finding vital mycorrhizae and decline intensity. Most mycorrhizal morphotypes were found to be distributed homogeneously in the different classes of decline. Some of them, however, can be associated with the degree of decline in a variable manner. Relationships between growth anomalies and mycorrhizal infection are also discussed.ProbabilitĂ© d'ectomycorhization du chĂȘne pĂ©donculĂ© dans une forĂȘt dĂ©pĂ©rissante. L'Ă©tude a Ă©tĂ© menĂ©e sur des chĂȘnes ĂągĂ©s de 50-55 ans croissant dans un Ornithogalo pyrenaici-Carpinetum betuli. Quatre classes de dĂ©pĂ©rissement des arbres ont Ă©tĂ© dĂ©terminĂ©es dont la premiĂšre comportait uniquement des arbres sains. Pour chaque classe, les apex racinaires mycorhizĂ©s et non mycorhizĂ©s ont Ă©tĂ© dĂ©nombrĂ©s dans des Ă©chantillons de racines prĂ©levĂ©es Ă partir de dix arbres et la probabilitĂ© de trouver des mycorhizes vivantes a Ă©tĂ© dĂ©terminĂ©e. Les morphotypes de mycorhizes ont Ă©tĂ© sĂ©parĂ©s et dĂ©crits et leur frĂ©quence a Ă©tĂ© calculĂ©e pour chaque classe de dĂ©pĂ©rissement. L'Ă©tude a dĂ©montrĂ© que la probabilitĂ© qu'un apex racinaire soit mycorhizĂ© est significativement plus Ă©levĂ©e pour les arbres sains que pour les arbres dĂ©pĂ©rissants. En revanche, parmi ces derniers, on n'a pas relevĂ© de correspondance entre la probabilitĂ© de trouver des mycorhizes viables et la sĂ©vĂ©ritĂ© du dommage. La plupart des morphotypes sont distribuĂ©s de façon homogĂšne parmi les diffĂ©rentes classes de dĂ©pĂ©rissement. Toutefois, quelques morphotypes semblent ĂȘtre associĂ©s de façon variable avec la sĂ©vĂ©ritĂ© du dĂ©pĂ©rissement. Les relations entre les anomalies de croissance et la mycorhization sont discutĂ©es
Vegetative compatibility and conversion to hypovirulence among italian isolates of Cryphonectria parasitica
pubblicato in Phytoparasitica 1994, 22/2: 17