The Effects of Culture Media and Sporulation Methods on Caducity and Pedicel Length of Sporangia in Selected Species of Phytophthora

SUMMARYFour species or morphological forms (MF) of Phytophthora, P. colocasiae, P. palmivora (MF1), and two atypical “P. palmivora” (MF3 and MF4) having intermediate, short, intermediate, and long pedicels, respectively, were studied for the effects of culture media and methods of sporangium production on the degree of sporangium caducity and pedicel length. Different media (carrot, V8-CaCO3, or oatmeal) as well as different methods of sporangium production (solid-agar plate, agar disc in water, or mycelial mat in water) affected the degree of sporangium caducity in some or all of the four phytophthoras tested. Except for “P. palmivora” (MF4), which possesses sporangia with long pedicels, different media and methods of sporangium production did not affect or slightly affected sporangium-pedicel length. Pedicel length is, therefore, a more stable morphological character of the sporangium than the degree of caducity (i.e., high or low % detachment) and is useful in the diagnosis and taxonomy of Phytophthora species.