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Ecology and Epidemiology

Influence of Temperature and Moisture on Growth of Gloeotinia temulenta and Infection of Annual Ryegrass. S. C. Alderman, Research plant pathologist, USDA-ARS National Forage Seed Production Research Center, 3450 SW Campus Way, Corvallis, OR 97331; Phytopathology 82:196-200. Accepted for publication 26 September 1991. 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, 1992. DOI: 10.1094/Phyto-82-196.

Germination, growth, and sporulation of Gloeotinia temulenta increased at temperatures of 5–20 C and then declined. No germination or growth occurred at 30 C. Germination of conidia slowed with decreasing water potential, although 95–100% germination occurred by 24 h at potentials of 0.0 through –4.0 MPa. Radial growth on potato-dextrose agar amended with sodium chloride, potassium chloride, or sucrose declined with decreasing water potentials through –9 to –10 MPa. Conidia were abundant with sucrose as an osmoticum but not with KCl or NaCl. Spore production on a sucrose-amended medium at 10, 15, or 20 C increased through –4 MPa and then declined through –10 MPa. Infection of annual ryegrass occurred at 15, 20, and 25 C but not at 30 C. A dew period was not required for infection when a drop of conidial suspension was placed in open flowers of annual ryegrass or when a conidia-laden exudate from infected seed was transferred to ovaries in open flowers. Production of conidia in infected seed at 20 C increased 6–16 days after inoculation.