VIEW ARTICLE

Soybean Phytoalexin, Hydroxyphaseollin, Induced by Ultraviolet Irradiation. M. A. Bridge, Graduate Assistant, Department of Botany, University of Maryland, College Park 20742; W. L. Klarman, Associate Professor, Department of Botany, University of Maryland, College Park 20742. Phytopathology 63:606-609. Accepted for publication 20 November 1972. DOI: 10.1094/Phyto-63-606.

The phytoalexin, hydroxyphaseollin (HP), was detected in soybean hypocotyls 12 hr after ultraviolet irradiation (^λmax = 253 nm) when plants were maintained in darkness. Maximal concentrations of HP occurred 96 hr after irradiation and relatively high levels were still present after 216 hr. Hypocotyls from irradiated plants maintained 12 hr in darkness and subsequently in light contained approximately one-half as much HP as hypocotyls from plants kept in constant darkness following irradiation. Hypocotyls from plants placed in light immediately after irradiation contained almost no HP. The concentration of HP remained high in irradiated plants placed in darkness for 48 hr and subsequently placed in light for 48 hr. When genetically susceptible plants were irradiated, they became less susceptible to the soybean pathogen, Phytophthora megasperma var. sojae.