Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2010
Publication Date: 12/1/2010
Publication URL: http://hdl.handle.net/10113/46337
Citation: Carson, M.L. 2010. Additional sources of broad-spectrum resistance to Puccinia coronata f. sp. avenae in Canadian accessions of Avena barbata. Plant Disease. 94:1405-1410. Interpretive Summary: Crown rust is the devasting disease of oat worldwide. Resistant cultivars are the best means of controlling the disease and reducing losses. However, the rust pathogen has the ability to quickly adapt to resistant oat varieties such that the effective lifespan of a newly released resistant variety is only five years. Oat breeders are running out of new resistance genes to use in this battle. Avena barbata, a wild relative of cultivated oats, has been found to be an excellent sources of new resistant genes that are effective against North American races of the crown rust pathogen. Accessions of A. barbata from the Canadian germplasm system have been found to have levels of resistance similar to those in the USDA Small Grains collection. A unique resistance phenotype was also observed in three Canadian accessions of A. barbata. This information provides oat breeders new sources of crown rust resistance to use in their oat improvement programs.
Technical Abstract: Crown rust (Puccinia coronata f. sp. avenae) is considered the most damaging disease of oat and the use of race-specific seedling (Pc) genes for resistance has been the primary means of control. As these resistance genes from cultivated oat, Avena sativa and the wild hexaploid animated oat, A. sterilis were deployed in oat cultivars, corresponding virulence in the U. S. crown rust population increased rapidly, such that the effective lifespan of a resistant cultivar in the U.S. is now five years or less. Introgression of resistance from diploid and tetraploid Avena species into hexaploid oat has been difficult due to the difference in ploidy levels and the lack of pairing of homeologous chromosomes between species. The wild tetraploid slender oat, A. barbata, has been a source of powdery mildew and stem rust resistance in cultivated oat, but has largely been unexploited for crown rust resistance. A relatively high percent of A. barbata accessions from the USDA National Small Grains Collection were resistant to a highly diverse crown rust population in recent tests. Tests of 1099 A. barbata accessions from the Canadian Plant Gene Resources Center not represented in the USDA collection revealed a similar percentage (11.4%) were at least moderately resistant at the seedling and adult plant stage when tested with a highly diverse bulk inoculum derived from the St. Paul buckthorn nursery. Eighteen accessions were rated as highly resistant or a mix of highly resistant and resistant plants in both seedling and adult plant tests. Three accessions (CN21531 from Italy, and CN26271 and CN26305 from Spain) displayed a unique "blotchy" resistant reaction as adult plants. Resistant accessions were found from throughout much of the natural range of A. barbata, but the Western Mediterranean and Lebanon had the highest frequency of accessions with broad-spectrum resistance.