VARIABILITY IN ASSOCIATION EFFECTS OF OTHER SOIL FUNGI ON THE VIRULENCE OFHELMINTHOSPORIUM SATIVUMON WHEAT SEEDLINGS

Abstract

Random isolates of Penicillium, Actinomyces, and certain miscellaneous soil-inhabiting fungi were tested in steam sterilized soil, under pure culture conditions, for their association effects on the virulence of Helminthosporium sativum P. K. and B. on wheat seedlings. Certain isolates of the first two genera mentioned exerted a marked degree of suppression, some had no effect, while others increased the virulence. Similarly, these effects varied widely within certain species of Penicillium. This preliminary study indicates that the random isolates of many genera and species of fungi may differ widely in ability to affect the virulence of certain plant pathogens.