Effect of Water and Temperature on the Oogonium and Oospore Formation of Peronospora manshurica in Lesions on Glycine soja

Abstract

Oogonia and oospores of Peronospora manshurica were proved to be formed in lesions on Glycine soja (G. ussuriensis) by immersion treatment in water at 10-20C. A few oogonia were formed by 3-day immersion at 15 and 20C, and their number increased by 4-day immersion at 10, 15 and 20C. The oogonium formation was most abundant at 15C. After the formation of oogonia, oospores were more rapidly formed when temperature was higher in the range of 10-20C. The size and shape of oospore formed by immersion treatment were identical to those hitherto reported on natural host, average diameter being 27.1μm.