MOLECULAR DIVERSITY OF FUNGI FROM ERICOID MYCORRHIZAL ROOTS

In order to investigate the diversity of fungal endophytes in ericoid mycorrhizal roots, about 150 mycelia were isolated from surface-steril ized roots of 10 plants of Calluna vulgaris. Each mycelium was reinocu lated to C. vulgaris seedlings under axenic conditions, and the phenot ype of the plant-fungus association assessed by light and electron mic roscopy. Many isolates that were able in vitro to produce typical eric oid mycorrhizae did not form reproductive structures under our culture conditions, whereas others could be identified as belonging to the sp ecies Oidiodendron maius. Morphological and molecular analysis of the fungal isolates showed that the root system of a single plant of C. vu lgaris is a complex mosaic of several populations of mycorrhizal and n on mycorrhizal fungi. PCR-RFLP techniques, used to investigate the myc orrhizal endophytes, revealed up to four groups of fungi with differen t PCR-RFLP patterns of the ITS ribosomal region from a single plant. S ome of the mycorrhizal fungi sharing the same PCR-RFLP pattern showed high degree of genetic polymorphism when analysed with the more sensit ive RAPD technique; this technique may prove a useful tool to trace th e spread of individual mycorrhizal mycelia, as it has allowed us to id entify isolates with identical RAPD fingerprints on different plants.