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Alteration of Germination Patterns of Sclerotia of Macrophomina phaseolina on Soil Surfaces. D. K. G. Ayanru, Former Postdoctoral Research Associate, Department of Botany and Plant Pathology, Purdue University, Lafayette, Indiana 47906, Present address of senior author: Department of Biological Sciences, Benin University, Benin City, Nigeria; R. J. Green, Jr., Professor, Department of Botany and Plant Pathology, Purdue University, Lafayette, Indiana 47906. Phytopathology 64:595-601. Accepted for publication 12 November 1973. DOI: 10.1094/Phyto-64-595.

Sclerotia of Macrophomina phaseolina on the surface of nonsterile soil exhibited an abnormal germination pattern (AG). An intermediate germination (IG) pattern was induced with sclerotia undergoing AG by amendment with appropriate nutrients. Sclerotia on nonsterile soil amended with 5 × 102 M concns of several sugars, amino acids and organic acids exhibited mainly normal germination (NG), and their germ tubes colonized the soil surface. Autoclaved soil induced NG (98%), but there was little colonization of the soil. The following sugars, amino acids, and organic acids effectively (80-98%) stimulated NG: maltose, D-ribose, DL-aspartic acid, glutamic acid, L-leucine, DL-phenylalanine, L-serine, citric, malonic, and tartaric acids. Lactose, L-cystine, urea, and all tested mineral salts were ineffective; DL-methionine was inhibitory at 5 × 102M. Continuous leaching of sclerotia in vitro was fungistatic. The NG of sclerotia of M. phaseolina in soil is apparently nutrient-dependent. Also, a nutrient-dependent mechanism is suggested which limits germ tube emergence and conserves the viability of these propagules.