Occurrence of Three Races of Xanthomonas campestris pv. vesicatoria on Pepper and Tomato in Taiwan. G. L. Hartman, Asian Vegetable Research and Development Center, Shanhua, Tainan, Taiwan, 74199, Republic of China. C. H. Yang, Asian Vegetable Research and Development Center, Shanhua, Tainan, Taiwan, 74199, Republic of China. Plant Dis. 74:252. Accepted for publication 10 October 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0252E.
Three races of Xanthomonas campestris pv. vesicatoria (Doidge)
Dye have been reported to cause bacterial spot of pepper (Capsicum
annuum L.) based on strains collected from various locations (1,2).
No report has been published on the races that occur in Taiwan,
even though bacterial spot is prevalent in most fields and causes losses
in quality and quantity. Diseased leaves and fruits were collected from
40 fields of pepper and 15 fields of tomato (Lycopersicon esculenium
Mill.) from 16 distinct areas of production between 1988 and 1989.
Bacteria were isolated on PDA, and single colonies were selected,
increased, and stored on slants of 523 medium. Cell suspensions
(5 X 108 cfu/ml) from 24-hr-old cultures grown on 523 medium were
infiltrated into the three youngest fully expanded leaves of 1-mo-old
pepper plants. A differential set of pepper lines with Bs1, Bs2 and
Bs3 genes and Early Calwonder (no known genes for resistance) were
used according to Hibberd et al (2). Hypersensitive reaction was
recorded within 48 hr after inoculation. Of the strains from pepper
70, 10, and 20% were races 1, 2, and 3, respectively. In contrast,
of the train from tomato, 13, 7, and 80% were races, I, 2, and 3,
respectively. The Bsl, Bs2, and Bs3 genes do not exist in commercial
pepper cullivar in Taiwan. Thus, races 1-3 are natural components
of the population and have not arisen because of selection pressure.