Phylogenetic placements and cultural characteristics of Tuber species isolated from ectomycorrhizas

Summary

Researchers successfully grew truffle fungi in the laboratory by isolating them from the roots of fir trees in Japanese forests. They identified eight different truffle species or lineages and studied how they grew on nutrient agar plates, finding that while they shared basic characteristics like white filamentous colonies, they had many differences in growth rates and hyphal structure. The study shows that collecting truffles from tree roots can be an effective way to obtain pure cultures of these fungi when fruiting bodies cannot be found.

Background

Tuber species are hypogeous fungi that form ectomycorrhizal associations with woody plants and have significant ecological and economic importance. Pure cultured mycelia are essential for understanding biological, physiological, and genetic properties of Tuber species, as well as for industrial applications. Isolation and maintenance of pure cultures of Tuber species has been generally difficult, though some species have been successfully isolated from ascomata and ectomycorrhizal root tips.

Objective

This study aimed to isolate pure cultures of Tuber species from ectomycorrhizal root tips of Abies sachalinensis plantations in Hokkaido, Japan, and to characterize their phylogenetic relationships and vegetative hyphal characteristics on culture media.

Results

Pure cultures were successfully isolated from EcM root tips, yielding 104 cultures with clear Tuber ITS sequences belonging to eight well-supported lineages within Puberulum, Latisporum, and Maculatum clades. All Tuber strains displayed yellowish white, thin, filamentous colonies on culture media with various differences in hyphal morphology, growth rates, and colony density. Morphological characteristics were not consistent within taxa, indicating that molecular techniques are necessary for species delimitation.

Conclusion

EcM root tips can be an effective isolation source for acquiring pure cultures of Tuber species, particularly when ascomata are unavailable. The study revealed Japanese truffle diversity and established that hyphal morphological characteristics are not reliable for species identification, necessitating phylogenetic analysis for accurate taxonomy.
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