Background:

Pinus (Coniferophyta) and Laccaria (Basidiomycota) establish ectomycorrhizal symbioses in natural forests. However, their detailed morphoanatomical and phylogenetic characterization have received little attention. Accurate identification of native host symbionts is of paramount relevance to the production of mycorrhized seedlings for successful reforestation programs.

Questions/Objective:

We aimed to determine if L. squarrosa is able to establish ectomycorrhizal symbiosis with gymnosperms, thereby widening its host range and highlighting its relevance as a potential inoculant for pine seedlings. Currently, L. squarrosa is only known from its type collection associated with the angiosperm Fagus grandifolia var. mexicana.

Studied species:

The fungus L. squarrosa and Pinus pseudostrobus, a tree endemic to Mexico.

Study site and dates:

A Pinus-Quercus forest in Piedra Canteada, Nanacamilpa, Tlaxcala; 2018-2020.

Methods:

L. squarrosa basidiomata were identified and ectomycorrhizal roots were collected and morphoanatomically characterized. For molecular identification, DNA was extracted, PCR was performed targeting the nuclear ribosomal internal transcribed spacer region (nucrDNA ITS) for the mycobiont identification and the chloroplastic single-locus trnL region for the phytobiont.

Results:

In the phylogenetic analyses, our sequences from basidiomata and ectomycorrhizae clustered together with L. squarrosa with high values of supporting identity. Meanwhile, P. pseudostrobus was molecularly identified as the phytobiont.

Conclusions:

This is one of the few worldwide characterizations of Laccaria ectomycorrhiza under field conditions and contributes to the understanding of the ecology, distribution, and economic relevance of the symbiotic association. Our data suggest that L. squarrosa has potential for use as a native inoculant for P. pseudostrobus tree production.

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