Abstract
A bacterial disease of carrot (Daucus carota L. var. sativa DC.) new to Japan was found in Tokushima prefecture during January 1978. Carrots are cultivated there in the plastic-film tunnels for their rapid growth. The disease starts during middle of January and severe infection occurs during February and March. It comes to an end during early in April after the film is removed. The disease was observed on leaves and petioles of carrots and the symptoms were very similar to those of leaf blight produced by Alternaria dauci. Disease severity was widely different with cultivars under natural infection: Kôki 200 was more severely attacked than Chanteney. Fifteen bacterial isolates obtained from affected leaflets proved to be pathogenic to carrot by artificial spray inoculation, producing similar symptoms to those produced naturally. The isolates were identical with each other in their bacteriological characteristics and coincided with the descriptions of Xanthomonas carotae and X. campestris and with the characteristics of check isolates of the latter species. The reciprocal inoculation experiments revealed that the check isolates of X. campestris did not attack carrots but Brassica spp., while the present isolates did not attack Brassica spp. On the basis of bacteriological characteristics and pathogenicity, the present isolates were identified as Xanthomonas carotae (Kendrick 1934) Dowson 1939. According to the proposal of Young et al., the bacterium is called X. campestris pv. carotae (Kendrick 1934) Dye 1978.
