A new bacterial disease was observed on leaves of broccoli (Brassica oleracea L. var. italica Plen.) in a field in Gunma Prefecture, Japan in 2001. The causal agent was identified as Xanthomonas campestris pv. campestris (Pammel 1895) Dowson 1939. Healthy seedlings were inoculated with the isolated bacterium, symptoms of the disease were reproduced, and the bacterium was reisolated from the margin of lesions on the leaves. We propose the name black rot of broccoli for the disease.
