A Factor controlling Sexual Reproduction in Phytophthora

Abstract

AN understanding of the physiology of reproduction in the fungus Phytophthora, one of the most important plant pathogenic genera, is hampered by there being no defined culture medium on which the sexual cycle can bo completed. The fusion organs are always obtained in culture by growing it on a variety of organic media the precise compositions of which are not known; oatmeal is perhaps used the most. The only attempt to extract from such media substances which are active in promoting production of oogonia and antheridia in Phytophthora appears to have been by Leonian and Lilly¹. They obtained from peas an unidentified fraction active down to 0.1 p.p.m. Zentmyer² reported stimulation of fusion organs in P. cinnamomi Rands by a non-protein extract from roots of avocado pear.