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Ecology and Epidemiology

Effect of Temperature, Dew Period, and Age of Leaves, Spores, and Source Pustules on Germination of Bean Rust Urediospores. Martin W. Imhoff, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650; C. E. Main(2), and K. J. Leonard(3). (2)Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650; (3)Plant pathologist, U.S. Department of Agriculture, SEA, AR, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 71:577-583. Accepted for publication 4 November 1980. 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, 1981. DOI: 10.1094/Phyto-71-577.

Urediospores of Uromyces phaseoli were incubated on wetted snap bean leaf disks resting on water agar in seed germination chambers. Minimal germination occurred at 10 and 25 C; none occurred at 4 and 27.5 C. Maximum germination, 93%, occurred within 17.522.5 C. At 1522.5 C, 90% of all germinations occurred within the first 68 hr of wetness. Spores stored 1421 days at 21 C in growth chambers showed little or no reduction in germinability. Spores from old leaves and old pustules germinated only two thirds as well as those from young leaves and young pustules. Germinability after interrupted wetting periods was reduced for well-spaced spores and increased for clumped spores. Spores wetted for at least 2 hr continued germination if relative humidity remained greater than 85%. Spores produced at 2427 C germinated about half as well as those produced at 16 or 21 C. Equations describing temperature-dew period interactions were developed. Effects of all other treatments could be expressed as fractional responses of the maximum germination at a given temperature and dew period.

Additional keywords: epidemiology, simulation.