Corky root of lettuce caused by Rhizorhapis suberifaciens in Japan

In 2017 and 2018, corky root disease was observed on lettuce ( Lactuca sativa L.) in Nagano Prefecture, Japan. The symptoms included corky, brittle, dark-brown lesions on the taproots and lateral roots, causing loss of feeder roots and wilting of plants. A bacterium was isolated from the roots lesions that caused similar symptoms in lettuce seedlings after inoculation. Based on the results of host range, bacteriological and phylogenetic analyses, the causal bacterium was identified as Rhizorhapis suberifaciens . To our knowledge, this is the first report of corky root on lettuce caused by R. suberifaciens in Japan.