VIEW ARTICLE

Characteristics of Asexual Sporulation in Phytophthora palmivora and Phytophthora parasitica nicotianae. R. Alconero, Research Plant Pathologist, Federal Experiment Station, Plant Science Research Division, ARS, USDA, Mayaguez, Puerto Rico 00708; A. Santiago, Biological Laboratory Technician, Federal Experiment Station, Plant Science Research Division, ARS, USDA, Mayaguez, Puerto Rico 00708. Phytopathology 62:993-997. Accepted for publication 7 March 1972. DOI: 10.1094/Phyto-62-993.

Sporangial and zoospore production in vitro was measured in two isolates of Phytophthora palmivora and two isolates of P. parasitica nicotianae. The greatest number of sporangia were produced on agar supplemented with nutrients under continuous light (50 ft-c) at 25 C for all isolates except IS7. On water agar, P. palmivora isolates did not produce sporangia under continuous darkness, but P. parasitica nicotianae isolates produced sporangia under continuous light or darkness. Many zoospores of P. palmivora were observed in flooded lima bean agar plates at 10 C, but few at 25 and none at 30 C. Phytophthora parasitica nicotianae were active at 10, 25, and 30 C. There was a wide range of sporangial sizes where indirect germination took place, even though most of the germinated sporangia were of average size of all sporangia produced in the medium. Apparently some of the zoospores observed in sporangia did not become active (swimming) in the solutions tested.