Germination of Conidia of Peronospora Tabacina Adam II. Germination in Vivo

Abstract

The percentage germination of conidia of Peronospora tabacina Adam on leaves and leaf disks of Nicotiana tabacurn L. cv. Virginia Gold ranged from less than 1 to 22% with a mean value of 1-7%. Addition of riboflavin-increased germination to a mean value of 44%. Prior washing of the leaf disks allowed 64% germination, which was increased to 95% on the addition of riboflavin, reaching a similar value to that recorded for conidia on agar. It is suggested that the degree of germination attained on N. labacum leaves is controlled by the amount of available riboflavin and by the presence of water-soluble compounds inhibitory to germination.