Abstract

Two experiments were conducted to examine the effects of temperature and light on the interaction between different genotypes of Avena and Puccinia coronata f. sp. avenae (Pca). In the first experiment, 45 oat lines were tested with two pathogenically distinct isolates of Pca under three temperature and two light regimes. Thirteen lines (Saia, Pc14, Pc46, Pc50, Pc61, Pc63, Pc68, C649, WIX, Amby, Bettong, Cleanleaf and Riel) showed resistant infection types (ITs) that did not change with temperature or lighting and six lines (Appler, Ukraine, Ruakura and Swan in all tests; Pc35 and Pc45 in all unshaded tests) were susceptible to both races at all temperatures. Twenty-three lines (Anthony, Bond, Landhafer, Santa Fe, Trispernia, Bondvic, Klein, Pc36, Pc38, Pc39, Pc48, Pc52, Pc55, Pc67, Pc71, H548, X534, X716, TAM-301, TAM-312, Culgoa, Enterprise and Nobby) displayed ITs that increased (became more compatible) with increasing temperature, and three lines (Victoria, Ascencao and Pc64) displayed ITs that decreased (became less compatible) at higher temperature. Shading resulted in small changes in IT on many host lines, and considerable reductions in IT on Anthony, Pc45, TAM-301, TAM-312, Pc35, Pc64 and Nobby. Interactions between temperature and shading were noted for some host/pathogen combinations. The second experiment examined the effect of temperature on interactions between 19 Pca isolates and oat genotypes used as Pca differentials from 1995 to 1999 at the Plant Breeding Institute, Cobbitty. The results were generally consistent with those of the first experiment, and clearly demonstrated that the temperature sensitivity of some genotypes was isolate-dependent. These results highlight the need for good light and temperature control in studies of pathogenicity of Pca and resistance in Avena in this host/pathogen system.