Disease Note First report of poor growth and root rot caused by Phytopythium helicoides on shiso grown in deep flow technique hydroponic system

Abstract

Abstract In 2023, shiso plant growth in a Deep Flow Technique (DFT) hydroponic system was delayed from mid-March to late April with roots showing evidence of rotting. An oomycete species was isolated from the roots and identified as Phytopythium helicoides based on morphological characteristics and DNA sequence homology. Identical symptoms appeared in shiso plants after inoculating seedlings with zoospores from the isolates. The same oomycete species were subsequently reisolated from diseased shiso plants. This study is the first report in Japan of poor growth and root rot in shiso grown in a DFT hydroponic system caused by P. helicoides.