GENETIC AND FUNCTIONAL DIVERSITY OF ERICOID MYCORRHIZAL FUNGI

Ericaceous plants are widespread on the globe and colonize substrates ranging from arid sandy soils to moist mor humus substrates. These pla nts also grow on soils polluted with metal ions, where toxicity is all eviated by the mycorrhizal fungal symbiont. A crucial point of current research on ericoid fungi is to understand whether this variety of en vironments corresponds to functional and genetic diversity of the asso ciated fungal symbionts. Interesting features of ericoid mycorrhiza ha ve derived from the genetic analysis of several fungal isolates: incre ased knowledge on their diversity has revealed that ericoid mycorrhiza can be very promiscuous, with multiple occupancy of the thin roots of ericaceous plants. Genetic diversity is also increased by the presenc e of several Group I introns in the nuclear 18S rDNA of most ericoid i solates, a feature rarely reported in eukaryotes. Biochemical analysis of hydrolytic enzymes produced by fungi from different environments a lso revealed diversity among isolates growing in polluted and non poll uted soils. These results indicate that ericoid mycorrhizal fungi cons titute a diverse population, both genetically and functionally.