Role and potentialities of bacteria associated with Tuber magnatum: A mini-review

Abstract

Among the hypogeous ectomycorrhizal fungi, the white truffle Tuber magnatum Picco is the species of greatest interest, both from an ecological and economic point of view. The increasing market demand of the precious white truffle along with the fall in its natural production led to a growing interest in cultivation techniques and encouraged truffle growers and researchers to deeper investigate factors that could affect and improve T. magnatum productivity. In this context, microbial communities play a central role. Indeed, in the last few years, the hypothesis of a potential link between microbial community composition and truffle orchard productivity is arousing a greater attention. Moreover, since the value of the prized T. magnatum can vary in relation to its provenience, the need to define a reliable tracking system is also emerging and bacteria appear to be a promising tool. Accordingly, the present mini-review summarises the knowledge currently available on T. magnatum microbial communities, focusing on the role of truffle-associated bacteria and highlighting similarities and differences between samples of different origin, to address the following issues: (i) Is there a correlation between microbial taxa and truffle ground productivity? (ii) Can bacteria actually be used as markers of T. magnatum geographic origin? The identification of microorganisms able to promote T. magnatum formation may represent an important advance in the field of truffle farming. Similarly, the detection of bacterial taxa that can be used as markers of T. magnatum origin could have a considerable impact on truffle industry and trade, even at local scale.

Tuber magnatum Picco: the challenge to identify ascoma-associated bacteria as markers for geographic traceability

“…Bacteria can heavily colonize truffle inner tissues (gleba) and the surface (peridium), reaching a density from millions to billions of cells per gram (dry weight) (Reale et al, 2009 ; Splivallo et al, 2015 , 2019 ; Vahdatzadeh et al, 2015 , 2019 ). A specific recruitment of selected genera from the soil microbial communities occurs before the differentiation of ascocarpic tissues, when the primordium is directly in contact with soil (Antony-Babu et al, 2014 ; Vita et al, 2020 ; Monaco et al, 2022 ). After the differentiation of the peridium, which remains in contact with ground throughout the ascoma development, bacteria remain trapped in the gleba (Antony-Babu et al, 2014 ; Monaco et al, 2020a ; Vita et al, 2020 ).…”

“…It is likely that the reduction of diversity and the exclusive presence of certain microbial groups inside the ascomata may be determined by a selective pressure on microorganisms related to specific potential functions and the evolutionary adaptation to the genus Tuber of some bacterial taxa (Marozzi et al, 2022 ; Sillo et al, 2022 ), testifying to their crucial role in truffle ecology and life cycle. On the other hand, “variable taxa”, “non-fixed” bacterial taxa that underlie specific differences observed among ascoma-microbial communities, can be associated with the “core microbiota” of T. magnatum (Monaco et al, 2021a , 2022 ). In our opinion, this is of upmost importance in the context of this article, since these “variable taxa” may represent microbial markers for geographic traceability.…”

“…This genus comprises more than 180 species distributed across Europe, North America, South East Asia and limited parts of Africa and South America (Bonito et al, 2010 ; Vita et al, 2015 ; Benucci and Bonito, 2016 ; Ye et al, 2018 ; Monaco et al, 2021a ). In addition to their ecological role, some truffle species are of considerable economic and commercial importance (Monaco et al, 2022 ). Tuber magnatum Picco, often known as the “Italian white truffle,” is the most expensive of all gourmet truffle species, with a retail price of thousands of euros per kilogram and a trade volume of around 0.9 billion euros per year (Graziosi et al, 2022 ; Monaco et al, 2022 ).…”

“…In addition to their ecological role, some truffle species are of considerable economic and commercial importance (Monaco et al, 2022 ). Tuber magnatum Picco, often known as the “Italian white truffle,” is the most expensive of all gourmet truffle species, with a retail price of thousands of euros per kilogram and a trade volume of around 0.9 billion euros per year (Graziosi et al, 2022 ; Monaco et al, 2022 ). High truffle prices have led to several forms of adulteration (Hamzić Gregorčič et al, 2020 ), including the addition of lower-value truffle species (e.g., T. borchii ) in place of T. magnatum (Oliach et al, 2021 ; Tejedor-Calvo et al, 2023 ).…”

The Mysteries of the White Truffle: Its Biology, Ecology and Cultivation

“…The microbiome and in particular bacteria seem to have not only a key role in T. magnatum aroma biosynthesis (see Section 3) but also in its mycelium soil development, mycorrhiza formation and fruiting body formation and nutrition [77,78].…”