Response of an International Triticale Collection to Puccinia triticina and Puccinia recondita sensu stricto and Assessment of Temperature Sensitivity in Leaf Rust Isolates

摘要

Triticale is derived from a cross between wheat and rye and the leaf rust pathogen of wheat, Puccinia triticina (Pt), and that of lye, P. recondita sensu stricto (Pr), can potentially cause disease in this crop. Recent studies showed that wheat rust fungi could adapt to warmer temperatures. In this paper, we report on the comparative virulence of three Pt races and one Pr isolate (all were collected in South Africa) on triticale as well as their in vitro response to temperature. Seedling infection types (SITS) of 169 triticale entries to Pt races 3SA144 (North American code SDDN), 3SA145 (CCPS) and 3SA248 (CFPS) and Pr isolate UVPr2 revealed that 3SA144 is the most virulent with 106 triticale entries found susceptible to this race. The three Pt races were avirulent to the four rye cultivars included as controls. UVPr2 was avirulent on all the triticale entries and 49 entries were considered resistant to the Pt races tested. Freshly harvested urediniospores of the above isolates were tested at constant temperature regimes of 10 degrees C, 22.5 degrees C and 35 degrees C to study germination characteristics. Mean urediniospore germination percentages as determined for 3SA144 (61.3%) and UVPr2 (62.6%) were significantly lower when compared to 3SA145 (83.7%) and 3SA248 (84.9%). Race 3SA144 was most sensitive to the higher temperature regime of 35 degrees C (5.2% germination). Among the investigated races, 35A144 showed significantly lower mean germ tube elongation rates at all three incubation temperatures. This is the first report of differences in temperature adaptation between Pt races from SA.