An-Najah Staff

Pythium isolates obtained from damped-off lucerne (Medicago sativa cv. SA Standard) seedlings were identified to species level using morphological criteria. The frequency of occurrence of features (modal positions) were calculated. Measurements of oogonium and oospore diam. were also made as part of the identification procedure. Three species were identified: P. irregulare, P. sylvaticum and P. ultimum var. ultimum. Intraspecific variation of diam. and other features used for taxonomic purposes sometimes occurred. It is suggested that variation might be reduced if the methods for preparation of material for identification were standardized, and that there should be a universal adoption of a single system of identification based on reliable features.