ARS | Publication request: Avena Barbata, a Potential Source of New Crown Rust Resistance in Oat

Submitted to: Phytopathology
Publication Type: Abstract
Publication Acceptance Date: March 10, 2008
Publication Date: May 3, 2008
Citation: Carson, M.L. 2008. Avena Barbata, a Potential Source of New Crown Rust Resistance in Oat. Phytopathology. 98:531.

Technical Abstract: The use of race-specific seedling genes for resistance has been the primary means of controlling crown rust of oat. As resistance genes from hexaploid cultivated oat, Avena sativa and later, the wild hexaploid animated oat, A. sterilis were deployed in oat cultivars, corresponding virulence in the crown rust population increased rapidly, such that the effective lifespan of a resistant cultivar is now five years or less. Introgression of resistance genes from diploid and tetraploid Avena species into hexaploid oat has been difficult due to differences in ploidy levels and the lack of homology of chromosomes between the two species. The wild tetraploid oat, A. barbata, has been a source of powdery mildew and stem rust resistance in oat, but has largely been unexploited for crown rust resistance. A total of 359 accessions of A. barbata from the National Small Grains Collection were evaluated in seedling greenhouse tests. Thirty-nine percent of accessions were at least moderately resistant when inoculated with a crown rust race with low virulence (DBBC). When tested further with a highly diverse bulk inoculum from the 2006 and 2007 St. Paul buckthorn nursery, 49 accessions (~14%) were resistant. Many of these accessions were heterogeneous in reaction, but several accessions were uniformly highly resistant in all tests. Resistant accessions were found from throughout much of the natural range of A. barbata. Initial crosses of some of the better accessions have been made to cultivated oat. We have also initiated screening of the Canadian germplasm collection of A. barbata, and similar levels of crown rust resistance are being observed.