Are Trechisporales ectomycorrhizal or non-mycorrhizal root endophytes?

Abstract

Trechispora (Hydnodontaceae) is considered as a soil-inhabiting fungus. However, some species in the genus are frequently forming basidiomes on soil, a typical feature of ectomycorrhizal fungi. Ectomycorrhizal basidiomes are found in neotropical and subtropical region, but taxonomical information and DNA sequences of root fungi and basidiomes from native Atlantic Rainforest are poorly reported. Basidiomes and soil samples including roots, humus layer, and mineral soil were collected in the Atlantic Rainforest, in Florianopolis (South of Brazil). Sequences of the ITS region were obtained from all sample types and subjected to phylogenetic reconstruction. Two sequences amplified from apparently ectomycorrhizal roots belonged to Trechispora and suggested a root-associated ecology, at least biotrophic and possibly ectomycorrhizal. The analysis of isotope abundance in the same Brazilian site and in French Guiana showed that Trechispora thelephora has high 15N abundance and is often intermediate between ectomycorrhizal and saprotrophic species in 13C abundance. This is congruent with a plant biotrophic ecology, perhaps ectomycorrhizal. Future investigations in subtropical regions are needed to determine whether such a mode of nutrition is widespread among Trechispora.