PHYSIOLOGICAL RACES OF VENTURIA INAEQUALIS

Abstract

Cultures of Venturia inaequalis were isolated from infected apple leaves and fruits received from various parts of Canada. The isolates differed in their ability to produce spores and to a certain extent in their growth. Variations were observed among monoconidial isolates obtained from a tissue isolate. Monoconidial cultures from an isolate varied in the shape, size, and colour of their colonies and in their pathogenicity to different varieties and seedlings. It would appear, therefore, that distinct physiological races of this fungus occurred among isolates tested.