INFECTIVITY OF THE PROPAGULES ASSOCIATED WITH EXTRARADICAL MYCELIA OF2 AM FUNGI FOLLOWING WINTER FREEZING

Abuscular mycorrhizal fungi are thought to survive adverse environment al conditions primarily as spores. ExtraradicaI mycelia of two Glomus species were produced in fine mesh pouches which excluded roots but no t hyphae. The mycelia in these pouches were exposed to freezing condit ions, either in the field or in a controlled-temperature chamber. Bioa ssay plants were grown directly in the pouches and mycorrhizal coloniz ation was assessed after 1 month. The mycelia remained infective in fr ozen soil over winter. This survival was not dependent on either the p resence of root pieces or on the connection of mycelia to roots. Spore s were not an effective inoculum in these bioassays. Overwinter surviv al of mycelia would enable plants to become incorporated into function al mycorrhizal associations early in spring.