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Phosphatidase of Sclerotinia sclerotiorum Produced in Culture and in Infected Bean. R. D. Lumsden, Research Plant Pathologist, Crops Research Division, ARS, USDA, Plant Industry Station, Beltsville, Maryland 20705. Phytopathology 60:1106-1110. Accepted for publication 27 February 1970. DOI: 10.1094/Phyto-60-1106.

Sclerotinia sclerotiorum produces an adaptive, extracellular phosphatidase in culture on autoclaved bean hypocotyls, but little, if any, when grown in a minimal medium with 1.0 or 0.5% soybean phosphatide (lecithin) as the carbon source. Slurries of diseased bean hypocotyl tissue contained appreciable phosphatidase activity early in pathogenesis, and the activity increased with increasing symptom expression. Enzyme activity was routinely assayed by measuring the release of acid-soluble organic phosphorus (P). Maximum release of P by the enzyme from culture filtrates or infected bean tissue was at pH 4.0. Activity was low or nondetectable below pH 3.0 and above pH 6.0, and was stimulated by 0.004 m CaCl₂. The presence of phosphatidase in infected tissue early in disease development suggests that it may play a role in pathogenesis.