AbstractConidium ontogeny of twenty‐three isolates of Pyricularia (including international races, some nutritional, coloured mutants and isolates obtained from cultivated and wild species of Gramineae) was studied. Among them, sixteen isolates were found to be of typical blastic type of conidiogenesis characteristic of the genus Pyricularia. Three coloured mutants and an international race showed gangliar type of conidiogenesis. However, two races and one nutritional mutant showed both the types.Most of the isolates tested are morphologically indistinguishable and potentially pathogenic with the respective hosts and on differential cultivars. Possible alteration of morphogenetic pattern of conidiogenesis by mutation and temperature response is suggested.