Evaluation location: Louisiana, United States
Oat Stem Rust Evaluations, Baton Rouge, LA. The research farm is located in the flood-plain on the banks of the Mississippi River. The weather is warm and wet, and provides an ideal environment for development of oat stem (Puccinia graminis f.sp. avenae) and crown rust (Puccinia coronata). Fog and dew are very common in the winter and spring, which provides the necessary free moisture for spore germination and disease development. A total of 11,021 entries were included in the nursery, including 10,300 NSGC Avena sativa accessions, crown and stem rust differentials spaced throughout the field, and breeding lines from programs in North Dakota, Minnesota, Illinois, and Ottawa. Differential lines and material of specific interest were scattered throughout the nursery. Every third range was entirely stem rust spreader material (mix of Trophy and Chapman). A spreader mix was planted across both sides of the field to ensure uniform inoculum spread. The nursery was planted in early December to permit optimum growth of winter and spring types. A single 1/2-rate of propaconizole (Tilt) was applied at early boot stage to delay the development of crown rust until temperatures warmed enough to equally favor development of stem rust. The winter of 2006-07 was warm with high rainfall amounts in January followed by a dry spring. Oat stem rust from natural inoculum first appeared in spreader rows in mid winter on the susceptible variety `Brooks'. Stem rust appeared on `Trophy' in March and continued to increase in severity through April. Since Trophy was resistant to stem rust prior to 2004, it is assumed that the stem rust on Trophy are the isolates with greater virulence genes that are of interest in this study. Crown rust developed in March and was severe on susceptible lines by early April. Stem rust continued to develop on Trophy and spread throughout the nursery. Most of the NSGC oat accessions in the nursery were quite susceptible to crown rust. By late spring (mid-April) approximately 75% of the accessions had severe crown rust infections. All accessions were rated for crown rust reaction in early April. Stem rust reaction was recorded in late April. Based on the results of testing in the 2006-2007 season a total of 621 oat accessions showing the most promising levels of resistance were retested in 2007-2008.