Ericoid mycorrhizal fungi: cellular and molecular bases of their interactions with the host plant

Abstract

A number of soil-borne fungi are able to form typical ericoid mycorrhizae with plants belonging to Ericales. Together with Hymenoscyphus ericae, the first isolate from roots of ericaceous plants, other fungal species belonging to the genus Oidiodendron and many sterile mycelia have been recognized as mycorrhizal by several authors. A high genetic diversity was even found when a population of ericoid mycorrhizal fungi isolated from a single plant of Calluna vulgaris was analysed with morphological and molecular techniques. Ericoid fungi have a relevant saprotrophic potential, as they can degrade several organic polymers present in the soil matrices. Different cell wall degrading enzymes, which are part of this arsenal and are produced in vitro by several ericoid fungi, have been investigated biochemically. Immunocytochemical studies on the production of pectin degrading enzymes during the infection process of host and non-host plants suggest that regulation mechanisms for the production of cell wall degrading enzymes in vivo may be a crucial step for the establishment of successful mycorrhiza with host plants. Key words: ericoid mycorrhizae, cell wall degrading enzymes, polygalacturonase, DNA-RAPD techniques.