THE NATURAL MICROFLORA OF THE SOIL IN RELATION TO THE FOOT-ROT PROBLEM OF WHEAT

Abstract

In these studies the natural microflora of the black loam soil typical of the Edmonton district of Alberta had a marked inhibitive action on the development of the wheat foot-rotting fungus Helminthosporium sativum when the latter was grown directly in this soil. The severity of foot-rot infection of wheat seedlings caused by this pathogene was correspondingly reduced as a result of this action. A trace of unsterilized soil serving as a source of the saprophytic soil organisms had almost as great an influence as a relatively large amount. A similar effect on Fusarium graminearum, another fungous pathogene which causes loot-rot of wheat, is indicated.Bacteria, actinomycetes and fungi isolated from black soil each had a suppressive action on H. sativum in the soil and reduced the severity of foot-rot infection caused by it, but the fungi were considerably more effective than the bacteria and actinomycetes tested. A combination of all of these organisms produced the most marked effect and one equivalent to that produced by the organisms of unsterilized soil.The significance of the results in connection with the foot-rot problem of wheat is briefly discussed and their possible bearing on other plant diseases caused by soil-borne pathogenes is mentioned.