Antagonistic Effects of Alternaria tenuis on Certain Root-fungi of Forest Trees

Abstract

Alternaria tenuis has been observed to produce antagonistic effects on a number of mycorrhiza-formers for ectotrophic tree species. The two active strains of A. tenuis tested were isolated from two forest nursery soils of the arable type in which this fungus is generally abundant. Reactions of the mycorrhizal mycelia to the antagonistic principle of A. tenuis were recorded for mixed cultures on a synthetic medium (glucose, 20 gm. ; magnesium sulphate, 0.1 gm. ; ammonium chloride, 0.5 gm. ; potassium dihydrogen phosphate, 1 gm. ; malt extract, 20 gm. ; agar, 15 gm. ; distilled water, 1,000 c.c.) in the following order of degree : Boletus granulatus, B. variegatus—markedly inhibited ; B. bovinus, Rhizopogon luteolus—inhibited ; B. scaber—mildly inhibited. The accompanying photograph demonstrates the condition of B. scaber eight weeks from inoculation.