VIEW ARTICLE

Physiology and Biochemistry

Reduction in Pisatin Sensitivity of Aphanomyces euteiches by Polar Lipid Extracts. J. Sweigard, Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908; H. D. VanEtten, Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908. Phytopathology 77:771-775. Accepted for publication 29 September 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-771.

Incorporation of a polar lipid extract from pea into growth medium decreased the pisatin sensitivity of Aphanomyces euteiches in both semisolid and liquid culture bioassays. This extract also decreased sensitivity to the phytoalexins maackiain and phaseollin. Lipids extracted from squash and bean were also effective. Pea lipids decreased the pisatin sensitivity of A. e. f. sp. phaseoli, a fungus not pathogenic on pea, but did not decrease the pisatin sensitivity of Fusarium solani f. sp. cucurbitae or Neurospora crassa. Commercially obtained phosphatidylcholine decreased the pisatin sensitivity of all four fungi tested. Experiments on the mechanism of the increased pisatin tolerance in A. euteiches suggested that phosphatidylcholine decreased the uptake of pisatin from the medium. The pea lipid extract did not have this effect. Neither phosphatidylcholine nor the pea extract stimulated pisatin demethylation. Attempts to purify the active component from the pea extract indicated that a mixture of compounds was required for the tolerance-enhancing effect.