THE EFFECT OF 2 ECTOMYCORRHIZAL FUNGI, PAXILLUS-INVOLUTUS AND SUILLUS-TOMENTOSUS, AND OF BACILLUS-SUBTILIS ON FUSARIUM DAMPING-OFF IN JACK PINE-SEEDLINGS

Two species of ectomycorrhizal fungi, Paxillus involutus and Suillus t omentosus, and a bacterial strain of Bacillus subtilis, were tested ag ainst Fusarium moniliforme, the causal agent of damping-off in jack pi ne (Pinus banksiana) seedlings. Both P. involutus and B. subtilis inhi bited in vitro growth of F. moniliforme. The culture filtrates of P. i nvolutus and B. subtilis were toxic to F. moniliforme, but chlamydospo re formation of F. moniliforme was observed. Greater jack pine seedlin g survival was observed when co-inoculated with P. involutus and B. su btilis than with F. moniliforme alone. S. tomentosus neither inhibited in vitro growth of F. moniliforme nor increased survival of jack pine seedlings against F. moniliforme. F. moniliforme reduced ectomycorrhi za formation on jack pine seedlings by P. involutus and S. tomentosus. The number of colony forming units of F. moniliforme was significantl y reduced when seedlings were inoculated with P. involutus and B. subt ilis alone or in combination. S. tomentosus, on the other hand, did no t reduce the number of colony forming units of F. moniliforme. The sup pression of F. moniliforme growth by P. involutus and B. subtilis invo lved production of antifungal compounds.