AN ASEXUAL VARIANT OF PHYTOPHTHORA-INSOLITA

All tested isolates of Phytophthora insolita and an unknown asexual Ph ytophthora species found in soil, ditch water, and diseased plant tiss ues in Taiwan produced ovoid, nonpapillate, nondeciduous sporangia on sporangiophores proliferating through an empty sporangium or in a nest ing fashion, and formed irregular as well as spherical hyphal swelling s. All tested Phytophthora isolates grew at an unusually high temperat ure of 39 degrees C, displayed similar or identical electrophoretic pa tterns of soluble proteins, and produced alpha(1) hormone. The ability of one isolate of P. insolita to produce oospores was decreased and t hat of another was lost completely during storage. The results suggest that all isolates of the asexual Phytophthora sp. tested were Phytoph thora insolita and were unable to produce oospores owing to a defect i n the physiological process of sexual reproduction.