First report from Japan of black root rot in Eustoma grandiflorum caused by Berkeleyomyces rouxiae

In 2025, lisianthus ( Eustoma grandiflorum [Raf.] Shinn.) plants in Kagoshima Prefecture, Japan, exhibited stunted growth and wilting. Dark brown–black lesions were observed on the roots, and most small feeder roots did not develop. The fungus isolated from the diseased roots was identified as Berkeleyomyces rouxiae using morphological and genetic analyses. Pathogenicity tests confirmed B. rouxiae is a causal agent. This is the first report of black root rot in lisianthus caused by B. rouxiae in Japan.