A COMPARATIVE STUDY OF OPHIOBOLUS GRAMINIS AND FUSARIUM CULMORUM IN SAPROPHYTIC COLONIZATION OF WHEAT STRAW

The competitive saprophytic ability of Ophiobolus graminis has been compared with that of Fusarium cultnorum. Test pieces of wheat straw were buried in maize-meal-sand inoculum mixed in various proportions with unsterilized soil, according to the technique already described by Butler (1953). Some possible sources of variation in the results obtained by this technique have been investigated. Saprophytic colonization of the straw tissues by Ophiobolus graminis appeared to decline as invasion progressed from the outer to the inner tissues, presumably owing to continued competition with other saprophytes. An experiment using as inoculum the stubble of plants naturally infected by O. graminis suggests that saprophytic colonization of wheat straw by the take-all fungus can occur only to a negligible extent in the field.