Damping-off of Lettuce Caused by Pythium aphanidermatum and the Influence of Temperature on Its Occurrence

Abstract

Damping-off of leaf lettuce (Lactuca sativa var. crispa) occurred in Ibaraki Prefecture in September, 2013. The causal agent was identified as Pythium aphanidermatum on the basis of morphology, suitable growth temperature and ribosomal DNA internal transcribed spacer (rDNA-ITS) region. We propose that P. aphanidermatum should be added to the pathogens of damping-off of lettuce. The degree of virulence, rot and wilt of leaves, and growth inhibition of plant, was more remarkable at relatively high temperature conditions.