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Disease Note.

Physiological Specialization in Sugarcane Rust (Puccinia melanocephala) in Florida. R. N. Raid, Department of Plant Pathology, University of Florida, Everglades Research and Education Center, Belle Glade 33430-8003. . Plant Dis. 73:183. Accepted for publication 21 November 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0183D.

Puccinia melanocephala H. & P. Sydow, causal agent of sugarcane rust, was first observed on Florida sugarcane (interspecific hybrids of Saccharum) in 1978 (2). Rust has since become an important disease, and screening for resistance has become an integral part of the breeding program. Cultivar CP78-1247, a progeny of a 1974 cross, showed rust resistance in every field test before 1985, at which time low numbers of sporulating pustules appeared on leaves at two of eight advanced-stage field locations. Still considered moderately resistant, CP78-1247 was released in September 1986 (1); its planting has risen to approximately 1,292 ha. During spring 1988, CP78-1247 showed extremely high rust susceptibility throughout south Florida, with necrotic areas in excess of 50% common on the top visible dewlap leaf. This sudden change in susceptibility suggests the presence of a new rust variant in Florida and supports the hypothesis that sugarcane rust races occur.

References: (1) J. D. Miller et al. Crop Sci. 28:576, 1988. (2) L. H. Purdy et al. Plant Dis. 69:689, 1985.