Abstract: To verify the possibility of developing a sampling method to accurately describe the Norway spruce ectomycorrhizal community at plant level, research was conducted in four comparable monospecific forests on healthy, mature and coeval Norway spruce trees. The results showed that the lowest number of tips per root core can characterize the community changes from site to site, with tree species, age and sampling design being constant. This highlights the importance of ectomycorrhizal species distribution, which is not an intrinsic character of ectomycorrhizal species, and probably changes with the environmental and fungal community features. The research demonstrated, in accordance with a theoretical ectomycorrhizal distribution, the effectiveness of an encoded geometrical sampling design consisting of the collection of 24 root samples from each of the four unrelated plants, along four perpendicular directions and at six fixed distances from the collar, and with the observation of 10 randomly selected ectomycorrhizal tips per sample.
Abstract: The composition and the structure of the ectomycorrhizal (EM) community were investigated in seven European beech coppices, and differing for the year of the lost cut (2-48 years), in Northern Italy. The research was conducted on the spatial and temporal distribution of the ectomycorrhizal species, to study if possible changes in the community could be correlated to the application year of these human practices, together with site variables (site slope, pH, C/N, C-org, N-org, soil moisture, exposure, altitude, and bedrock type). The preliminary results indicated that ectomycorrhization degree significantly changes between the organic and mineral horizons. The ecological indexes of richness and evenness showed significant variations in the sampled sites but were not correlated with either coppicing age or slope. EM species composition revealed a significant correlation with slope and soil moisture but not with shoot age. The coppice treatment seems to he not dangerous for the EM community structure, but additional studies are necessary to understand the possible application of the "short rotation" practices in this ecological context, as a sustainable activity, according to the new trends in European Union energetic policies. An EM resilient condition is supposed.
Abstract: The study was carried out in 4 similar Norway spruce stands and it demonstrated that the spreading structures produced by Lophodermium piceae and Rhizosphaera kalkhoffii are not correlated. The two fungi were always detected with opposite growth trends, probably due to different needle colonization and spreading strategies, and this was most likely also why they were able to co-exist, colonizing different parts of the needle. Independently of the year, site, sampling period and amount of precipitation, the two fungi were significantly less common in saplings and more common in mature trees, with frequencies also depending on both the minimum and the maximum temperatures.
Abstract: The species composition of ectomycorrhizal (ECM) fungal communities can be strongly influenced by abiotic and biotic factors, which determine interactions among the species such as resource partitioning, disturbance, competition, or relationships with other organisms. To verify whether ectomycorrhization of the root tips and composition of the ECM community in Norway spruce vary according to site features and if ECM species peculiar to these environmental variables can be detected, ten comparable stands differing in bedrock pH and exposure were selected and studied. The results demonstrated that tips vitality and ectomycorrhization degree do not change significantly either on the same tree, or among trees growing in the same stand, whereas they differ greatly with bedrock pH and exposure, even if no spatial or temporal trend were found. ECM species composition revealed instead a significant connection with the two environmental features, with a few species significantly associated to them. The results suggest that pH/exposure patterns play a primary role in the adaptive selection of ECM species constituting the consortium.
Abstract: The vertical distribution of the ectomycorrhizal (ECM) community was studied in four old high-mountain Norway spruce (Picea abies [L.] Karst.) stands in northern Italy. The aim was to verify if the variability in the community structure could be explained by characteristics of the organic and mineral soil horizons. The community structure was evaluated in terms of both fungal species and their ability to explore soil (exploration types). From the 128 humus profiles sampled over the two study periods, 31 ECM species were recorded. The study demonstrated that the number of both non-vital tips and vital non-mycorrhized tips decreases with soil depth, from organic to mineral horizons, while the number of ectomycorrhizal tips mainly increases with soil depth. A preference was found of some ECM species and exploration types for specific organic or mineral soil layers and their features, especially moisture and available nitrogen. These results can help in understanding how the functional role of the single consortia and the ecological features determining this "adaptive diversity" in ectomycorrhizal communities could be of major importance to assess the resilience in forest soil ecosystems.
Abstract: The spatial distribution of vital root tips and ectomycorrhizal (ECM) communities in forest soils is characterized by patchiness at a microscale level, mostly related to the distribution patterns of biotic and abiotic factors. A geostatistical model was applied to verify if spatial analyses could be useful in identifying an appropriate sampling method to study root tip vitality, ectomycorrhization and the ECM community. Root samples were collected from two high mountain Norway spruce forests (Trentino province, Italy) following a geometrical design. Laboratory microscopic and geostatistical ordinary kriging analyses were used to map tip vitality and ectomycorrhization degree, ECM richness and distribution grouped in exploration types (amount of emanating hyphae or presence and differentiation of rhizomorphs). Spatial gradients of the examined features existed at plant level, associated to the up-downslope direction (root tip vitality and ectomycorrhization, ECM richness) and distance from the stem base (ECM exploration types). The effectiveness of the geostatistical model used demonstrates that a geometrical sampling design, associated to spatial mapping techniques, can be useful in research where the tree, and not the forest, is the subject (mycological and phytopathological studies).
Abstract: The effects of a sylvicultural treatment (thinning) on the ectomycorrhizal community structure and diversity were studied each season for 2 years in a declining Quercus robur woodland in northern Italy. Sixteen dominant oak trees were chosen as representative of two decline classes (eight per class). Fine root status, ectomycorrhizal community composition and structure were analysed before and after drastically altering tree density by felling all the neighbouring trees of four selected trees in each decline class. The ectomycorrhizal community was found to be extremely rich, with numerous infrequent species: of the 64 anatornotypes found, only 23 were present both before and after the thinning treatment, demonstrating that community structure changes rapidly after disturbance. Following an initial reduction, 10 months after removing competition and independently of health status, the biodiversity had recovered its previous level, demonstrating the high resilience of the ectomycorrhizal community to disturbance. (c) 2007 Elsevier B.V. All rights reserved.
Abstract: In a declining oak forest, a thinning treatment was performed in August 2004, targeting trees belonging to two decline classes. The whole ectomycorrhizal (EM) community was dominated by the fungal symbionts Clavulina cinerea, Tomentella sublilacina and Russula spp. The potential activities of eight secreted enzymes, involved in mobilizing nutrients (N, P) from soil organic matter, were measured on these three EM types in winter and spring 2006 using multiwell microplate photometric and fluorogenic methods. The enzymatic activities recorded in winter were generally significantly higher than in spring. Most of the enzyme activities studied, and particularly phosphatase and beta-glucosidase, changed according to both decline class and sylvicultural treatment. In spring, each anatornotype displayed different enzymatic profile according to the decline class. These results suggest that the potential enzymatic activity of ectomycorrhizae adapts to the changes resulting from the sylvicultural treatment and reacts to the anthropic disturbance by adjusting to the new resource structure. (c) 2007 Elsevier Ltd. All rights reserved.
Abstract: Phytophthora cactorum (Lebert et Cohn) Schroeter is an important plant pathogen that can cause serious damage in agricultural and ornamental crops as well as in a wide range of forest species. The identification of this pathogen, based on morphological and physiological characters, is time consuming, labour-intensive and requires specialised staff to be correctly performed. Recently, PCR-based methods have partially resolved these problems, but the primers used cross react with Phytophthora idaei. To prevent any such reaction the use of a new pair of primers (PC1/PC2) with improved specificity, derived from a specific Random Amplified Polymorphic DNA (RAPD) generated fragment, is proposed. The PC1/PC2 primers, used in a simple PCR protocol, gave a single amplification product of approximately 450 bp; a good degree of specificity, with absence of cross reactions with Phytophthora pseudotsugae and R idaei; sensitivity down to 6 pg of R cactorum DNA extracted from pure mycelium; no reactions with the DNA of the host plants tested (downy oak, pear and walnut trees, potato, strawberry, tomato and pea plants). The detection of R cactorum in infected tissues of pear and walnut trees, potato, strawberry, tomato and pea plants was also confirmed. The specificity, sensitivity and robustness of the PC1/PC2 primers together with the possibility of their use in a rapid, simple and reliable diagnostic method are discussed.
Abstract: 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.
Abstract: A total of 850 virulent isolates of Cryphonectria parasitica were isolated from natural cankers on European chestnut trees growing in various Italian regions. Vegetative-compatibility (v-c) group membership was tested using the merge-barrage method. In all, 19 vegetative-compatibility groups were found, and, for each of these, a representative isolate (v-c tester) was identified; 49% of the Isolates were compatible with the tester of only one v-c group, whereas 51% were compatible with the testers of more than one v-c group; 3% of the isolates showed compatibility with seven v-c groups. The coincidence between vegetative incompatibility and failure of conversion occurred in only a few cases; 42% of the converts were stable with respect to their morphological characteristics ana presence of cytoplasmic ds-RNA. The results obtained in Italy suggest that, for an efficient biocontrol programme, it is preferable to evaluate the tendency of a population to be converted rather than evaluating the v-c group membership.
