Domizia Donnini

Truffles in the genus Tuber (Pezizales) are among the few ectomycorrhizal taxa successfully cultivated worldwide. Australia has recently become one of the top producers of Tuber melanosporum , a high-valued black truffle native to Europe. Truffle co-introductions in the Southern Hemisphere with their Northern Hemisphere plant symbionts are hypothesized to benefit from reduced ectomycorrhizal competition and natural enemies. In this study, we tested whether T. melanosporum in Australia experiences competition release by sampling soils and truffles across France, Spain, Italy, and Australia. Fungal and prokaryotic communities in truffle plantations were assessed in native (European) and non-native (Australian) habitats through ITS and 16S rDNA amplicon sequencing from soil and truffles. Community composition was primarily structured by site of origin and secondarily by presence of brûlé, vegetation-free area induced by truffle production of plant-growth inhibiting compounds, with significant interactions indicating site-dependent brûlé effects. European soils showed higher fungal richness outside the brûlé, with higher evenness overall and for ectomycorrhizal fungi only outside brûlé. T. melanosporum showed higher abundance in Australia, with significant differences restricted to outside the brûlé. Overall, ectomycorrhizal fungi in European soils had more than four times the taxa and higher diversity compared to Australian soils. Among the main competitors, Tomentella , Inocybe , and Trichophaea co-dominated in Europe, versus Scleroderma , Hebeloma , and Tarzetta in Australia. Despite differences in soil microbiomes, bacterial communities within T. melanosporum truffle ascocarps were strikingly similar across sites and continents and were dominated by Bradyrhizobium . Despite high site-level variation, our results support the competition release hypothesis, with reduced enemies benefiting T. melanosporum colonization outside the brûlé in Australia. IMPORTANCE: This study provides the first cross-hemisphere analysis of the truffle microbiome, comparing native and non-native soils and truffles from Europe and Australia. We demonstrate that the remarkable success of Tuber melanosporum cultivation in Australia is compatible with ecological release from competitors, which favors its development outside the brûlé. At the same time, we reveal striking cross-hemispheric similarities in truffle-associated bacterial communities, consistently dominated by Bradyrhizobium . These findings highlight both the novelty and transcontinental relevance of our work, offering new perspectives on fungal ecology and truffle cultivation.

Truffles are valuable underground mushrooms with significant economic importance. In recent years, their cultivation has achieved satisfactory results, but not for all species. The harvesting of white truffles (Tuber magnatum Picco) is still dependent on natural production, which is at risk due to various issues, such as improper forest management. A useful practice to protect natural resources is to promote the expansion of productive forests. In this study, we investigate the dynamics of the microbiome in an old and new truffle forest using an amplicon sequencing approach of the fungal ITS region and the prokaryotic 16S rRNA gene. We monitor the soil biological community’s development to compare differences and similarities between the primary productive forest and the expanding area over a two-year sampling period. In particular, we observed the colonization of vacant ecological niches by certain fungi, such as those belonging to the genus Mortierella. Additionally, we examined the competitive interactions between saprotrophs and ectomycorrhizal fungi (ECM). In both study areas, the bacterial community was dominated by Pseudomonadota, Planctomycetota, and Actinomycetota. The behavior of the Tuber genus differed significantly from other ECMs and displayed positive correlations with bacterial taxa such as Ktedonobacter, Zavarzinella, and Sphingomonas. The present work provides an initial overview of expanding white truffle habitats. Further, more specific research is needed to explore potential connections between individual taxa.

Although only a few species of Tuber account for the major truffle sales volume, many species that are not considered delicacies are finding their way to the market, especially in regions where the traditionally appreciated ones do not occur. This is the case for whitish truffles. Specimens of whitish truffles were collected in pecan (Carya illinoinensis) orchards in Uruguay in October 2021. Morphological and molecular methods were used to characterize and assess their identity as Tuber maculatum Vittad. An SPME extraction of volatile compounds and GC–MS analyses were performed to characterize the aromatic profile of these specimens and evaluate their potential applications. Among the 60 VOCs detected, 3-octenone (mushroom odor), 3-octanol (moss, nut, mushroom odor), and 2H-pyran-2-one (no odor), followed by octen-1-ol-acetate (no odor) and 2-undecanone (orange, fresh, green odor) were the major compounds in T. maculatum fruiting bodies. The attributes of exotic edible mushrooms of commercial value in the region are highlighted. In particular, this work emphasizes the characteristics of truffles as a byproduct of pecan cultivation.

Seminatural grasslands are among the most threatened habitats in Europe and worldwide, mainly due to changes in/abandonment of their traditional extensive use by grazing animals. This study aimed to develop an innovative model that integrates plant biodiversity, animal husbandry, and geo-informatics to manage and preserve seminatural grasslands in protected areas. With this objective, an integrated study was conducted on the seminatural grasslands in the hilly, montane, and (to a minimum extent) subalpine belts of the Maiella National Park, one of Europe’s most biodiversity-rich protected sites. Plant biodiversity was investigated through 141 phytosociological relevés in homogeneous areas; the pastoral value was calculated, and grasslands’ productivity was measured together with the main nutritional parameters. Uni- and multivariate statistical analyses were performed to identify the main grassland vegetation types, their indicator species and ecological–environmental characteristics, and their pastoral and nutritional values’ variability and differences. A total of 17 grassland types, most of which correspond to habitat types listed in Annex I to the 92/43/EEC Directive, were identified and characterised in terms of their biodiversity and potential animal load. To allow for near-real-time analysis of grasslands, an NDVI-based web interface running on Google Earth Engine was implemented. This integrated approach can provide decision-making support for protected-area managers seeking to develop and implement sustainable grassland management practices that ensure the long-term maintenance of their biodiversity.

Fungi belonging to the genus Tuber produce edible ascocarps known as truffles. Tuber magnatum Picco may be the most appreciated truffle species given its peculiar aroma. While its life cycle is not yet fully elucidated, some studies demonstrated an active role of microorganisms. The main goal of this study was to determine how the T. magnatum microbiome varies across space and time. To address this, we characterized microbial communities associated with T. magnatum through high-throughput amplicon sequencing of internal transcribed spacer (ITS) and 16S rDNAs in three productive natural sites in Italy across 2 years. At each site, four truffles were sampled as well as the soil underneath and at 40, 100, and 200 cm from the harvesting points, to assess for microbial variation between substrates, years, and sites. A statistically significant site-related effect on microbial communities was identified, whereas only the prokaryotic community was significantly affected by the distance of soil from the truffle. Significant differences between sampling years were also found, demonstrating a possible relation among rainfall precipitation and Firmicutes and Actinobacteria. Thirty-six bacterial OTUs in truffles and 11 bacterial OTUs in soils beneath truffles were identified as indicator taxa. As shown for other truffle species, the dominance of Bradyrhizobium, Rhizobium, and Ensifer spp. within the truffle fruiting body suggests an evolutionary adaptation of this microorganism to the genus Tuber. The present work offers novel and relevant insights into the microbial ecology of T. magnatum ecosystems and fruiting bodies. The function and role of these bacteria in the truffle microbiome and life cycle are in need of further investigation.

Tuber aestivum, one of the most sought out and marketed truffle species in the world, is morphologically similar to Tuber mesentericum, which is only locally appreciated in south Italy and north-east France. Because T. aestivum and T. mesentericum have very similar ascocarp features, and collection may occur in similar environments and periods, these two species are frequently mistaken for one another. In this study, 43 T. aestivum and T. mesentericum ascocarps were collected in Italy for morphological and molecular characterization. The morphological and aromatic characteristics of the fresh ascocarps were compared with their spore morphology. Afterwards, we amplified and sequenced the elongation factor 1-α (EF1α) locus and built maximum likelihood trees to assess phylogenetic similarities between the two species. Tuber aestivum and T. mesentericum sequences cluster into different clades, with T. mesentericum sequences divided into three different sub-clades. According to their morphological features, three samples (T7, T8 and T12) were classified as T. mesentericum. However, when fresh, these ascocarps lacked the typical phenolic aromatic note. These specimens fall into the sub-clade III of the T. mesentericum phylogeny, which has the lowest genetic distance from the T. aestivum clade.