Induction of infection in Sesbania exaltata by Colletotrichum gloeosporioides f. sp. aeschynomene formulated in an invert emulsion

摘要

In greenhouse experiments, an invert emulsion (MSG 8.25) was tested with spores of the mycoherbicidal fungus Colletotrichum gloeosporioides f. sp. aeschynomene, a highly virulent pathogen of the leguminous weed Aeschynomene virginica (northern jointvetch), but considered “immune” against another leguminous weed, Sesbania exaltata (hemp sesbania). A 1:1 (v/v) fungus/invert emulsion mixture resulted in 100% infection and mortality of inoculated hemp sesbania seedlings over a 21 day period. Microscopic examinations revealed that the fungus proliferated within the cells of hemp sesbania and produced anthracnose lesions containing acervuli on infected stems. The fungus was reisolated and found to infect and kill northern jointvetch seedlings, thus fulfilling Koch’s postulates for disease identification. These results suggest that this invert emulsion expands the host range of C. gloeosporioides f. sp. aeschynomene, and possibly improves the bioherbicidal potential of this pathogen.