MECHANISMS CONTRIBUTING TO THE ERADICATION OF SPORES OF HELMINTHOSPORIUM SATIVUM FROM AMENDED SOIL

Abstract

Declines in population of spores of Helminthosporium sativum in amended soil were due to disappearance that occurred in normal soil and to eradication brought about by the germination–lysis mechanism and by an increase in antagonism. Germination–lysis played a major role in molasses- and vitamin C-amended soils but not in glucose-amended soil, as was evidenced by the density of spore populations in the soils at intervals over a 16-week period.Antagonism which was increased in all three amended soils was responsible to a lesser extent for the eradication of the spores. The data suggest that antagonism was more effective during the early, than during the later, stages in the breakdown of the amendment. A close correlation was noted between spore population and the incidence of seedling infection. Correlation between spore population and disease ratings was much less significant.