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Sporulation and Germination of Phytophthora lateralis. Edward J. Trione, Agricultural Research Service, U.S. Department of Agriculture, Dept. of Botany and Plant Pathology, Oregon State University, Corvallis 97331; Phytopathology 64:1531-1533. Accepted for publication 8 July 1974. DOI: 10.1094/Phyto-64-1531.

In culture on seven different agar media, the growth rate of Phytophthora lateralis increased from 3 to 20 C, then decreased at 25 C. Moisture was essential for the induction of sporangia, which developed only when vegetative growth ceased or was reduced to a minimum. Mature sporangia remained firmly attached to sporangiophores and liberated 25-40 fully developed zoospores. In contrast to sporangia, abundant production of chlamydospores depended on rich media. On a medium containing a protein hydrolysate, chlamydospores averaged 51 µm in diameter and germinated readily by producing several germ tubes. Oospores were produced on media containing cedar foliage and averaged 40 µm in diameter. A single paragynous antheridium was formed per oogonium. Colonies arising from single zoospores produced oospores, demonstrating the homothallic nature of this fungus.

Additional keywords: sporangia, chlamydospores, oospores, Chamaecyparis, white cedar.