Isolation, Purification, and Biological Activity of a Self-Inhibitor from Conidia ofColletotrichum gloeosporioides

Abstract

Low concentrations of conidia (104/ml) of C. gloeosporioides f. sp. jussiaea germinated readily, but high concentrations of conidia (107/ml) in water or on water agar germinated poorly. Aqueous extracts from high concentrations of conidia inhibited germination of dilute concentrations of conidia. An inhibitor [gleosporone] was extracted from these extracts with chloroform. TCC of the chloroform extracts gave a single spot of inhibition in assays on the chromatograms. Chloroform extracts were taken to dryness, and the inhibitor was crystallized from hexane as fine colorless needles, melting point of 108.degree.-110.degree. C. Germination of conidia was reduced by .apprx. 50% at 2 .mu.g of inhibitor/ml. Dilutions of the purified inhibitor or conidial exudates gave germination percentages that paralleled those of dilutions of conidia. Chemical analysis revealed a molecular formula of C18H30O5 and a molecular structure quite different from other known germination self-inhibitors.