Phytophthora megasperma causing Pink Rot of the Potato

Abstract

DURING the course of an investigation into the occurrence and distribution of pink rot of the potato in Northern Ireland, a species of Phytophthora other than P. erythroseptica, the normal cause of the disease in the field, was isolated from tubers involved in an outbreak of the disease at Culnafay, County Antrim. Numerous isolations made between 1928 and 1932 from diseased tubers occurring in the same field at Culnafay have proved to be P. erythroseptica, the species referred to having been obtained on one occasion only. The isolation was made in January, 1930. A series of inoculation experiments has shown that this species causes a tuber rot of the potato indistinguishable from that caused by P. erythroseptica. The isolation was found to differ from P. erythroseptica mainly by the production of a preponderance of paragynous antheridia and in the large size of its oospores. We are grateful to Mr. Ashby of the Imperial Mycological Institute who has identified it as P. megasperma Drechsler.