Two New Hosts of Xanthomonas campestris pv. vitians.

Bacterial leaf spot of lettuce (Lactuca sativa L.) caused by Xanthomonas campestris pv. vitians (proposed new names X. axonopodis pv. vitians / X. hortorum pv. vitians) is an economically important disease in many areas of the world (1,2). Serious outbreaks occurred in Ohio in 1995 and 1996. The primary sources of the causal agent are presumed to be contaminated seed and infected plant debris in the field. Once the disease is present in a field, crop rotation is required to decrease primary inoculum of the pathogen. Therefore, appropriate crop rotation sequences need to be determined based on the host range of the pathogen. Some vegetable crops, including tomato, pepper, cabbage, collard, kale, radish, and horseradish, were tested for susceptibility to four representative strains of X. campestris pv. vitians by spray inoculation in the greenhouse. Typical symptoms of bacterial leaf spot were observed on tomato and pepper plants 8 days after inoculation, whereas the other crops did not develop diagnostic symptoms. The pathogen was reisolated and Koch's postulates were completed on tomato and pepper. This is the first report that X. campestris pv. vitians strains can cause bacterial spot disease on tomato and pepper. References: (1) C. L. Patterson et al. Plant Dis. 70:982, 1986. (2) L. Vauterin et al. Int. J. Syst. Bacteriol. 45:472, 1995.