Predominance of Race 18 of Xanthomonas campestris pv. malvacearum on Cotton in Australia. S. J. Allen, Narrabri Agricultural Research Station, New South Wales, Australia 2390. K-L. D. West, Cotton Seed Distributors Ltd., Wee Waa, New South Wales, Australia 2388. Plant Dis. 75:43-44. Accepted for publication 7 May 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991. DOI: 10.1094/PD-75-0043.

All of the 67 strains of Xanthomonas campestris pv. malvacearum collected from commercial cotton crops in New South Wales over a 5-yr period (1983–1988) and in Queensland in one season (1984–1985) were found to be race 18. Races 1–5, 7, 9, and 10 of the blight pathogen which had been recorded on cotton in Australia before 1980 were not detected in this study. The predominance of race 18 has been associated with severe epidemics of bacterial blight on susceptible cotton cultivars and has resulted from the aggressiveness of the pathogen and from the reliance of the Australian cotton industry on a single source of planting seed. New cultivars with resistance to race 18 are now becoming widely grown.