Characterization of Xanthomonas campestris pv. pennamericanum pv. nov., causal agent of bacterial leaf streak of pearl millet

A survey for bacterial diseases of millet and sorghum was conducted in northern Nigeria during the 1984 growing season. Bacterial diseases were prevalent throughout the area surveyed. Yellow, mucoid bacterial colonies were consistently isolated from pearl millet leaves exhibiting bacterial streak symptoms. The causative organism was characterized as a pathovar of Xanthomonas campestris. The strains isolated formed a homogeneous group of aerobic, motile, gram-negative, rod-shaped organisms which were distinctly different pathologically, serologically, and by membrane protein patterns from other pathovars of X. campestris. The cells measured 0.45 by 2.25 μm, and each cell had one polar flagellum. Optimal growth occurred between 26 and 30°C, and the maximum NaCl tolerance was 3%. Pearl millet (Pennisetum americanum) and Proso millet (Panicum miliaceum) are the only known hosts. For this pathovar, we propose the name Xanthomonas campestris pv. pennamericanum pv. nov. (the name is derived from Pennisetum americanum, the Latin binomial for pearl millet). The holopathotype strain is strain B6-P, which has been deposited in the American Type Culture Collection, Rockville, Md.