Studies on Agglutination-Inhibitory Substances on Germinated Spores of Ceratocystis fimbriata, Black Rot Fungus

Abstract

Ungerminated spores of the sweet potato strain of Ceratocystis fimbriata are highly sensitive to spore-agglutinating factor (SA factor) from sweet potato roots and are agglutinated by the factor at low concentrations. However, they become less sensitive to the factor when they germinate. The substances (SAI substances) that inhibited spore agglutination by SA factor were released by sonication from the surface of germinated spores of the sweet potato strain and isolated. The substances seemed to re-bind efficiently onto the surface of the sonicated spores at pH 6.5 in the presence of Ca²⁺ (10mM) and this made them less sensitive to SA factor. The substances were assumed to be proteins from the inactivation by heat and trypsin treatments. The substances diminished, to a similar degree, the sensitivity to SA factor of germinated spores of all seven strains of C. fimbriata ; the sweet potato, coffee, prune, cacao, oak, taro, and almond strains. The substances stimulated the growth of sweet potato, coffee, cacao, and taro strains in liquid media, while the growth of prune, oak, and almond strains were inhibited by the substances. These results are discussed in relation to differential agglutination of germinated spores of various strains by SA factor and to host-parasite specificity.