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Ecology and Epidemiology

Production and Partial Characterization of Antifungal Substances Antagonistic to Monilinia fructicola from Bacillus subtilis. C. D. McKeen, Biological technician, U.S. Department of Agriculture, Agricultural Research Service, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, GA 31008; C. C. Reilly(2), and P. L. Pusey(3). (2)(3)Research plant pathologist, and research plant pathologist, respectively, U.S. Department of Agriculture, Agricultural Research Service, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, GA 31008. Phytopathology 76:136-139. Accepted for publication 21 August 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1986. DOI: 10.1094/Phyto-76-136.

Antibiotic substances produced by a strain of Bacillus subtilis previously found to suppress development of brown rot of stone fruit were produced in a synthetic medium and isolated from the cell-free medium by precipitation by acidification to less than pH 2.5. Impurities were removed by extraction with ethyl acetate and acetone. The active fraction was extracted from the precipitate with 80% ethanol. This extract contained antibiotics that were soluble in ethanol, methanol, isopropanol, and water above pH 7.5; but not soluble in ethyl acetate, acetone, ether, or methylene chloride. Thin-layer chromatographic separation of the extract indicated four biologically active bands. The extract was active against a wide range of plant pathogenic fungi and was fungistatic, not fungicidal, against spores of Monilinia fructicola. When tested for activity against M. fructicola on peach fruit, the extract showed almost complete suppression of brown rot at 1 mg/ml.