Bacterial brown blotch, a disease of rice in tropical America

Abstract

A bacterial disease of rice not described previously has been observed in Central and South America. Symptoms are characterized by spreading brown blotches on the leaves. Systemic invasion by the pathogen causes necrosis of the vascular system of the leaves, resulting in their partial or total browning. Under greenhouse conditions, lesion enlargement is generally slower than that of bacterial leaf blight. The pathogen grows on media containing different sources of carbohydrates. Colonies on Wakomoto and Yoshii medium are round, entire, and dark yellow, easily distinguishable from those of Xanthomonas campestris pv. oryzae on the same medium. Although the organism has the general characteristics of members of the genus Xanthomonas, several physiological and biochemical characteristics are different from those reported for X. campestris pv. oryzae. Similarly, resistance to this organism is not correlated with resistance to the causal agent of bacterial blight of rice.