Reaction of Sweet Corn Germ Plasm to Common Rust and an Evaluation of Rp Resistance in Illinois. Jerald K. Pataky, Assistant Professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 71:824-828. Accepted for publication 7 May 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0824.

Several sources of rust resistance were identified in sweet corn (Zea mays) germ plasm. The Rp₁^d gene probably is carried in yellow (IL125b and IL791a) and white (IL18c) sweet corn inbreds. An Rp type of resistance that may be conditioned by Rp₁^d was observed on IL763a. Other rust-resistant reactions (type 1 and type 2) were identified on several lines. A purple pigmentation surrounding a resistant reaction was observed on IL677a and several lines derived from IL677a. Chlorotic infection types were observed on several other lines for which Country Gentleman was an ancestor. The Rp₁^d, Rp₁^e, Rp₁^f, Rp₁^g, Rp₁ⁱ and Rp₃^c genes conditioned type 0; resistant reactions when inbreds possessing those genes were infected with a mixture of Puccinia sorghi biotypes collected in Illinois in 1983 and 1985. In greenhouse trials, these genes were effective against a mixture of P. sorghi biotypes collected from California, South Dakota, Nebraska, Minnesota, Wisconsin, Ontario, Illinois, Ohio, New York, and Georgia. The Rp₁^k gene conditioned a type 1 reaction to all biotypes in field and greenhouse trials.