Studies on Ectomycorrhizae of Pine II. Growth Inhibition of Mycorrhizal Fungi by Volatile Organic Constituents of Pinus silvestris (Scots Pine) Roots

The effects of several monoterpenes and the sesquiterpene longifolene on the vegetative growth of two mycorrhizal fungi, Boletus variegatus and Rhizopogon roseolus, were studied in petri plate experiments on an agar medium. The test substances are natural constituents of Pinus silvestris (Scots pine) roots. Vapors from 20 μl of all the test substances, upon a 5 day exposure inhibited the growth of both the mycorrhizal fungi 55% to 86%. The two fungi, however, differed in their tolerance to individual compounds. It is suggested that the terpenes and the sesquiterpenes play an important role in the development of the symbiotic condition in ectomycorrhizae by restricting the growth of the mycorrhizal fungi within the host root.