Synthesis and ultrastructural observation of arbutoid mycorrhizae of black truffles (Tuber melanosporum and T. aestivum)

Abstract

Arbutus unedo (the strawberry tree) is a Mediterranean shrub which forms arbutoid mycorrhizae with a variety of Asco- and Basidiomycetes. After the discovery of the mycorrhizal symbiosis between A. unedo and Tuber borchii, in this study, arbutoid mycorrhizae were synthetized in greenhouse with Tuber aestivum and Tuber melanosporum. Six months after inoculation, both species colonized the roots of all inoculated A. unedo seedlings, but mature mycorrhizae were only observed after 12 months. Ultrastructure analysis of Tuber arbutoid mycorrhizae was described for the first time, showing, as observed in typical endosymbiosis, a rearrangement of host cells and the creation of an interface compartment with both truffle species. Immunolabelling experiments suggested that pectins are not present in the interface matrix surrounding the intracellular hyphae. Thus, the ability to establish symbiosis with A. unedo seems to be a common feature in the genus Tuber, opening up the possibility to use this plant for mycorrhization with valuable truffles. This could represent an important economic opportunity in Mediterranean areas by combining the production of truffles, edible fruits and valued honey.

Production and marketing of Tuber floridanum – ecology and gastronomic value of a recently described truffle species

“…All known truffle species are ectomycorrhizal (Rinaldi et al, 2008) or can form ectendomycorrhizal or endophytic relationships under specific conditions. Truffles form mycorrhiza with trees and shrubs and rarely interact with non-ectomycorrhizal plants in natural environments (Ori et al, 2020;Schneider-Maunoury et al, 2020;Nahberger et al, 2021). Besides vital mycorrhizal plant partners, most truffle species require specific soil conditions to prosper and fruit, such as neutral to alkaline pH (Hall et al, 2007;Ge et al, 2017), high concentration of available calcium, and low organic matter contents (Hall et al, 2007;Zambonelli et al, 2017).…”

Effect of earthworms on mycorrhization, root morphology and biomass of silver fir seedlings inoculated with black summer truffle (Tuber aestivum Vittad.)

“…Truffles are ectomycorrhizal 9 , ectendomycorrhizal 10 or endophytic fungi 11 that are unable to complete their life cycle without a symbiotic relationship with a vital plant host 3 , 12 . Truffles grow in an ectomycorrhizal symbiosis with most boreal and temperate trees, and with perennial shrubs of the northern hemisphere, such as oaks, hazel, beech, birch, pines, pecan, cistus, sunrose, etc.…”

“…13 – 17 . The only known example of forming ectendomycorrhizae is with the strawberry tree 10 . High cultural, gastronomic, and economic interest in truffles guided many attempts of truffle cultivation.…”