Pathogenic Variation in<i>Puccinia substriata</i>var.<i>indica</i>in the Southeastern United States and Screening for Resistance in Pearl Millet Germ Plasm

Abstract

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 11 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.