Characterisation and identification of ectomycorrhizae formed by the species of Asproinocybe (Tricholomataceae) and Inocybe (Inocybaceae) with the roots of the tropical sal tree Shorea robusta (Dipterocarpaceae)

Abstract

In the course of the present study, surveys on occurrence and distribution of ectomycorrhizal (EcM) fungi in tropical sal forests of foothills of the Himalayas, India, were undertaken. The species of two genera of agarics, namely Asproinocybe and Inocybe, were found organically associated with the roots of Shorea robusta (sal tree). However, prior to our study the genus Asproinocybe has not been reported from India. In this article, the morpho-anatomical details of mycorrhizal roots of Shorea robusta associated with Asproinocybe lactifera and Inocybe purpureoflavida are provided for the first time. The EcM colonized roots of the two species are distinguished by differences in the shape and colour of the roots, surface texture, size and shape of cystidia, type of mantle, as well as different chemical reactions. Asproinocybe lactifera EcM is mainly characterised by a monopodial pinnate mycorrhizal system with the dark brown to reddish brown and loose cottony surface, while in Inocybe purpureoflavida it is irregularly pinnate to coralloid, silvery grey to reddish brown, with densely woolly surface. The outer mantle layer is heterogeneous with obclavate to awl-shaped cystidia in Asproinocybe lactifera, whereas Inocybe purpureoflavida EcM have a plectenchymatous outer mantle with subcylindrical to obclavate metuloidal and non-metuloidal cystidia. The presence of lactifers in the mantle is a unique feature in Asproinocybe lactifera as compared to Inocybe purpureoflavida.

Asproinocybaceae fam. nov. (Agaricales, Agaricomycetes) for Accommodating the Genera Asproinocybe and Tricholosporum, and Description of Asproinocybe sinensis and Tricholosporum guangxiense sp. nov.

“…We do not know if they form mycorrhizal relationships with plants, but they usually have white rhizomorphs. Recently, Asproinocybe lactifera was reported as an ectomycorrhizae fungus [46]. This is worthy of further study, but finding species of Asproinocybaceae is challenging.…”

“…Asproinocybaceae was an important lineage in the evolution of agarics. The presence of laticifers, lamellae bruising reddish, and spores with ornamentation and ectomycorrhizae [46] led to us link it with Russulaceae, Lactarius. The species of Lactarius also have basidiomata shapes similar to those of species of Asproinocybaceae, but the spores of Lactarius are amyloid.…”

“…Species from Callistosporiaceae are saprotrophic or ectomycorrhizal [38]; as the sister family, species from Asproinocybaceae may be ectomycorrhizal [46]. The new species proposed here were collected from karst areas, where the soil is thin and infertile, where stony desertification is common, and where it is difficult for the vegetation to recover.…”