Heterogeneity of the white truffle Tuber magnatum in a limited geographic area of Central‐Southern Italy

Abstract

Summary Molise region (Central‐Southern Italy) is one of the Italian richest areas of truffles and contributes significantly to the national production of the precious Tuber magnatum. Nevertheless, Molise truffle has received little scientific attention. Accordingly, in the present study, two T. magnatum populations collected in two different sites of Molise region were characterised from a morphological, genetic and microbiological point of view. A considerable variability between and within the two analysed groups emerged, suggesting an interesting heterogeneity of Molise white truffle populations. Ascocarps of the two groups significantly differed in size and maturation degree, although no linear correlation between weight and maturity was found. Genetic investigations focused on the Sequence‐Characterised Amplified Region SCAR A21‐inf. Three haplotypes, randomly distributed within the two truffle groups regardless of their collection sites, were detected. The 16S rRNA gene amplicon high‐throughput sequencing provided an overview of the composition of the ascocarp‐associated bacterial communities. A predominance of α‐Proteobacteria was observed, with Bradyrhizobium among the main genera. However, some truffles showed unusual microbial profiles, with Pedobacter, Polaromonas and other bacterial genera as dominant taxa.

Global diversity and distribution of mushroom‐inhabiting bacteria

“…These taxa have been suggested to include phosphate‐releasing and iron‐releasing mycorrhiza‐helper bacteria (Pointing et al ., 2009). Moreover, the former class comprises mostly oligotrophic bacteria with potentially relevant functions for host fungi, such as denitrification and nitrogen fixation (Barbieri et al ., 2010; Gohar et al ., 2020; Monaco et al ., 2021). Nevertheless, it remains unclear whether the observed host effect on the community structure of MIB stems from host–microbe co‐evolution or intrinsic (e.g.…”

“…bisporus when grown in commercial substrates could reshape its original bacterial community (Carrasco et al ., 2020) which later may contribute to the core MIB community (Vieira and Pecchia, 2021). Microbial communities associated with other eukaryotes vary across geographic locations (Arnold and Lutzoni, 2007; Aslani et al ., 2020; Lin et al ., 2020; Monaco et al ., 2021), and such variations have been attributed to the local climatic conditions, the soil microbial community, as well as microbial nutrition source (Van Geel et al ., 2018; Dong and Gupta, 2019). Other studies have found that the community structure of the free‐living microbiome is distinct from the host‐associated microbiome in which ecosystem type was a secondary determinant of community structure (Thompson et al ., 2017; Bahram et al ., 2021b).…”

“…The prevalence of these taxa in mushrooms may be related to their ability to adapt to the dynamic nutrient availability during the life cycle of the fruiting body and perform functions that are important for fruiting body growth and development. For example, it has been suggested that Bradyrhizobium , one of the main bacterial genera associated with fruiting bodies of Tuber and some other fungi, could contribute to the nutrition of the fungus due to its nitrogen‐fixing activity and could affect the mushroom's aroma through the production of volatile sulphur compounds (Splivallo et al ., 2015; Monaco et al ., 2020; Monaco et al ., 2021).…”

“…Mushrooms represent an important source of food for various arthropods (Põldmaa et al ., 2016) and vertebrates, including humans (Valverde et al ., 2015; Senchik et al ., 2020) while hosting diverse microbial communities that collectively form the fungal microbiome (Antony‐Babu et al ., 2014; Pent et al ., 2017; Liu et al ., 2018). There is increasing evidence that mushroom‐inhabiting bacteria (MIB) play important functional roles for their hosts, by altering mushroom fruiting body development (Citterio et al ., 2001; Barbieri et al ., 2010; Gohar et al ., 2020) and aroma (Splivallo et al ., 2015; Splivallo et al ., 2019; Monaco et al ., 2021), improving the dispersal of spores (Citterio et al ., 2001; Splivallo et al ., 2015) and producing vitamins and growth regulators (Rangel‐Castro et al ., 2002a; Riedlinger et al ., 2006).…”

Black Truffles Affect Quercus aliena Physiology and Root-Associated nirK- and nirS-Type Denitrifying Bacterial Communities in the Initial Stage of Inoculation

“…For example, inoculation with Tuber spp. changed the nitrogen content in ectomycorrhizosphere ( Li et al, 2018 ; Yang et al, 2019 ), possibly due to the enrichment of nitrogen cycle-related bacteria in the truffle ascocarps ( Barbieri et al, 2010 ; Vahdatzadeh et al, 2015 ; Monaco et al, 2021 ), ectomycorrhizae, and mycorrhizosphere ( Beatrice et al, 2012 ; Le-Roux et al, 2016 ). Denitrification is a key nitrogen-transforming process which results in nitrogen loss in soil ( Bárta et al, 2017 ).…”