First report of crown rot on lettuce caused by Phytophthora crassamura in Japan

Abstract

During harvest in August 2017, wilting lettuces with crown rot were observed in Kagawa Prefecture, Japan. Fungi with aseptate hyphae were isolated from the rotted crowns. Based on phylogenetic analyses, morphological characteristics, and minimum, maximum, and optimum temperatures for hyphal growth, the isolate was identified as Phytophthora crassamura. This is the first report of lettuce crown rot caused by P. crassamura in Japan. We propose the name crown rot of lettuce (retasu eki-byo in Japanese) for this lettuce disease.