Sabrina Tempesta

Comparison of ectomycorrhizal communities in natural and cultivated Tuber melanosporum truffle grounds

Truffles are hypogeous ectomycorrhizal (EM) fungi belonging to the genus Tuber. Although outplanting of truffle-inoculated host plants has enabled the realization of productive orchards, truffle cultivation is not yet standardized. Therefore, monitoring the distribution of fungal species in different truffle fields may help us to elucidate the factors that shape microbial communities and influence the propagation and fruiting of Tuber spp. In this study, we compared the fungal biodiversity in cultivated and natural Tuber melanosporum truffle fields located in Central Italy. To this end, ectomycorrhizas (ECM) and soil samples were molecularly analyzed, and an inventory of the fungi associated with Quercus pubescens plants colonized by T. melanosporum, Tuber aestivum or Tuber brumale was compiled. T. melanosporum and T. aestivum were dominant on the cultivated plants, and the number of EM species was markedly lower in the cultivated sites than in the natural sites. However, in the same site, EM biodiversity was higher in T. brumale-colonized plants than in T. melanosporum-colonized plants. These results suggest that different Tuber spp. may have different competitive effects on the other mycobionts. Additionally, in keeping with our previous findings, we found that the number of T. melanosporum genotypes recovered from the soil samples was higher than that of the underlying ECM.

DNA-Based Taxonomy in Ecologically Versatile Microalgae: A Re-Evaluation of the Species Concept within the Coccoid Green Algal Genus Coccomyxa (Trebouxiophyceae, Chlorophyta).

Coccomyxa is a genus of unicellular green algae of the class Trebouxiophyceae, well known for its cosmopolitan distribution and great ecological amplitude. The taxonomy of this genus has long been problematic, due to reliance on badly-defined and environmentally variable morphological characters. In this study, based on the discovery of a new species from an extreme habitat, we reassess species circumscription in Coccomyxa, a unicellular genus of the class Trebouxiophyceae, using a combination of ecological and DNA sequence data (analyzed with three different methods of algorithmic species delineation). Our results are compared with those of a recent integrative study of Darienko and colleagues that reassessed the taxonomy of Coccomyxa, recognizing 7 species in the genus. Expanding the dataset from 43 to 61 sequences (SSU + ITS rDNA) resulted in a different delimitation, supporting the recognition of a higher number of species (24 to 27 depending on the analysis used, with the 27-species scenario receiving the strongest support). Among these, C. melkonianii sp. nov. is described from material isolated from a river highly polluted by heavy metals (Rio Irvi, Sardinia, Italy). Analyses performed on ecological characters detected a significant phylogenetic signal in six different characters. We conclude that the 27-species scenario is presently the most realistic for Coccomyxa and we suggest that well-supported lineages distinguishable by ecological preferences should be recognized as different species in this genus. We also recommend that for microbial lineages in which the overall diversity is unknown and taxon sampling is sparse, as is often the case for green microalgae, the results of analyses for algorithmic DNA-based species delimitation should be interpreted with extreme caution.

Succession of microfungi in Phillyrea angustifolia litter in a Mediterranean maquis in Sardinia

ABSTRACT The colonisation of microfungi in litter bags with Phillyrea angustifolia L. leaf litter was followed for two years; the succession of microfungal communities was analysed. Two main groups of fungi were identified, whose presence is correlated with the successive decomposition stages of the substrate and with seasonal variations.

Pestalotiopsis Endophytes from Leaves of Two Orchid Species Collected in Costa Rica

Abstract A survey of endophytic Pestalotiopsis associated with two orchid species collected in Coco Island in Costa Rica was carried out. Among the fungi isolated from leaves of the two species, genus Pestalotiopsis prevailed. We isolated 29 strains of Pestalotiopsis, 9 of which from Camaridium micranthum M. A. Blanco and 20 from Ornithidium adendrobium (Rchb.f.) M.A. Blanco. On the basis of morphological characters, Pestalotiopsis isolates were divided into three different groups but their high similarity do not allow unambiguous species identification. The analysis of internal transcribed spacer (ITS) region of ribosomal DNA was then performed to evaluate the taxonomic position of our isolates.

Ecofriendly synthesis of halogenated flavonoids and evaluation of their antifungal activity

Brominated and chlorinated flavonoids belonging to different classes (flavanones, flavones and catechins) were prepared from the corresponding flavonoids by a simple and ecofriendly procedure based on the use of sodium halides, aqueous hydrogen peroxide and acetic acid. Pure samples of substrates and products were tested against Trichoderma koningii, Fusarium oxysporum and Cladosporium cladosporioides, common saprotrophic soil and seed fungi, potential pathogens for humans and their activity was expressed as linear mycelial growth inhibition (%). Among them, 8-chloro-5,7,3′,4′-tetramethoxyepicatechin 29, a novel catechin derivative, exhibited a remarkable effect against all tested fungi also at low concentrations.

Succession of microfungi during Pistacia lentiscus litter decomposition in a Sardinian Mediterranean maquis

Abstract Changes in the microfungal community developing on Pistacia lentiscus L. leaf litter were monitored from February 2001 (senescent leaves) to December 2002 using litter bags. The Principal component analysis of the 16 samples showed a microfungal succession related to the progressive decomposition of the substratum. The Correspondence analysis of fungal colonizers with Rf > 10 revealed three main groups succeeding during the study period. The co-occurrence relationships (on the same leaf) among the major colonizers were analysed. The specialized saprotrophs on P. lentiscus litter: Asterostomella sp. 1 and Endophragmiella boewei were identified as principal colonizers in the mature community.

Effects of Long-Term Heavy Metal Contamination on Soil Fungi in the Mediterranean Area

Abstract The lead (Pb) and zinc (Zn) content in soil can qualitatively and quantitatively affect the microbial community and, therefore, the normal functioning of the soil ecosystem. The aim of this study was to assess the effect of long-term Pb and Zn contamination on soil fungi isolated by the dilution plate method, also in relation to vegetal topsoil. We analysed soil samples collected near dominant plant species (Pistacia lentiscus L., Quercus ilex L., Arbutus unedo L., and Phillyrea angustifolia L.) in soils suffering from heavy metal pollution as well as in unpolluted sites. The study area is located in the mining district of Ingurtosu (South-West Sardinia), where the polluted sites were severely contaminated by lead extraction activities that probably began before the Roman era. The obtained data were subjected to multivariate analysis, using Canonical Correspondence Analysis, to determine the relationship between the soil biota and the environmental variables. High concentrations of lead and zinc, with some variation with respect to the vegetation, were found in the topsoil of all polluted sites. Soil pollution places stress on sensitive microorganisms, which causes a change in the diversity of soil mycota. A significant decline in micro-fungal abundance was observed in all polluted soils tested in this study. In addition, some interesting fungal species are discussed.

Saprotrophic litter fungi in a Mediterranean ecosystem: Behaviour on different substrata

Saprotrophic fungi sporulating on 17 types of leaf litter collected during the dry season in the Sardinian Mediterranean area were analysed. The fungal assemblages identified in each substratum showed an overlap value ranging from 5.9% to 46.7%. A consistent connection between certain fungal species and their substrata was detected; among the 168 fungal species identified, 104 (62%) may be regarded as specialised. Each fungal species was characterised according to morphological and ecological features. Multidimensional scaling showed that ubiquitous and common species have morphological characters distinguishing them from specialised species.

Gliomastix macrocylindrica, a mycoparasite of Beltrania rhombica

ABSTRACT Gliomastix macrocylindrica Matsush. is a destructive parasite of Beltrania rhombica Penz. A light and electron microscopic observation on natural substratum revealed that G. macrocylindrica is an invasive specialised necrotroph. It grows inside the host conidiophores and conidiogenous cells. Colonisation of vegetative hyphae and specialised penetration structures, like pseudoappressoria and appressoria, were not observed.