Saprophytic Behaviour Of Some Cereal Root‐Rot Fungi

Abstract

Factors influencing the saprophytic colonizing ability of two cereal root‐rot fungi, Curvularia ramosa, a vigorous competitive saprophyte, and Helminthosporium sativum, a weak competitive saprophyte, have been investigated. The observed difference in their competitive saprophytic ability could not be ascribed either to a difference in rate of growth or to the ability of the stronger saprophyte, C. ramosa, to produce an antibiotic. The weaker saprophyte, H. sativum, proved, however, to be more sensitive than C. ramosa to antibiotics produced by other soil micro‐organisms. Thus, in spore germination tests with purified fungal antibiotics in vitro, H. sativum proved more sensitive to eight of the ten substances tested than did C. ramosa and was only slightly less sensitive than C. ramosa to the remaining two antibiotics. H. sativum was found also to be generally more sensitive than C. ramosa to the antagonistic effects of certain common soil bacteria. Of the seven bacterial species tested, five caused an appreciable reduction in germ tube development and two reduced germination in H. sativum whereas none of the bacterial species inhibited either spore germination or germ tube development of C. ramosa, and three actually stimulated germ tube development by this fungus.