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Pathogenic Variation in Puccinia substriata var. indica in the Southeastern United States and Screening for Resistance in Pearl Millet Germ Plasm. H. Tapsoba, Department of Plant Pathology, University of Georgia, Athens 30602. J. P. Wilson, Research Plant Pathologist, USDA-ARS Forage and Turf Research Unit, University of Georgia Coastal Plain Experimental Station, Tifton 31793-0748. Plant Dis. 80:395. Accepted for publication 15 December 1995.. This article is in the public domain and not copyrightable, ll may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1996. DOI: 10.1094/PD-80-0395.

Rust caused by Puccinia substriata var. indica can be very damaging on pearl millet in the southeastern United States. Breeding rust-resistant pearl millet cultivars is complicated by unknown pathogenic variation in the pathogen population. In the present study, 15 single-uredinial isolates of the pathogen were evaluated for pathogenic variation on seedlings of 29 resistant pearl millet germ plasm lines. Eleven races were identified based on seedling reactions. The reaction of the races on the germ plasm lines ranged from virulence to 15 lines to virulence to all 29 lines. Although some lines were susceptible to all races, others were resistant to as many as seven races and constitute new potential sources for genetic resistance. Field studies conducted in 1993 and 1994 indicated that most of the ll races are probably not yet predominant in the pathogen population at Tifton, Georgia, since some lines susceptible to many races showed low levels of disease in the field. These races will be important as tools for future screening in pearl millet germ plasm for additional sources of resistance to P. substriata var. indica.