Light-Cholesterol Relationships in Morphogenesis of Phytophthora Palmivora and P. Capsici Sporangia

Exogenous sterols are essential for sexual (4, 5, 7, 8, 9, 12, 13, 14) or zoosporangial (3, 9) reproduction of the Pythiaceae, a family of lower fungi pathogenic to plants. These fungi apparently are unable to synthesize the sterols commonly found in nature (10). Among the species of Phytophthora for which a sterol requirement for zoospore production was demonstrated were isolates of P. palmivora (Butl.) Butl. and P. capsici Leonian (9). Aragaki and Hine (1) found that light greatly stimulated sporangium formation by an isolate of P. parasitica Dast.; they also observed in limited studies that P. palmivora responded similarly to light. Harnish (6) observed a similar effect with an isolate of P. capsici. These workers used natural media in their studies.