|TINKER, NICHOLAS - Agriculture And Agri-Food Canada
|BEKELE, WUBISHET - Agriculture And Agri-Food Canada
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2022
Publication Date: 2/3/2022
Publication URL: https://handle.nal.usda.gov/10113/7709513
Citation: Gordon, T.C., Jin, Y., Tinker, N.A., Bekele, W.A., Gale, S.W., Bockelman, H.E., Bonman, J.M. 2022. Comparative sequencing and SNP marker validation for oat stem rust resistance gene Pg6 in a diverse collection of Avena accessions. Theoretical and Applied Genetics. 135(4):1307-1318. https://doi.org/10.1007/s00122-022-04032-z.
Interpretive Summary: Oat stem rust is a devastating foliar disease of oat. Identification of new sources of oat stem rust resistance is an important oat breeding objective as new races of stem rust overcome known resistance genes. A broadly-effective oat stem rust resistance gene, Pg6, was previously identified from a diploid oat (Avena strigosa) accession, CIav 6956. The Pg6 resistance locus was mapped to a 15 million base pair (Mbp) region on A-genome chromosome AA2 and validated using two bi-parental populations. Comparative sequencing within the 15 Mbp region found over 1000 SNPs associated with the Pg6 phenotype. One of these SNP markers was perfectly associated with the Pg6 phenotype in the two populations and closely linked in a diverse group of Avena spp. accessions. The SNP marker was used to postulate the presence of Pg6 in the diverse panel of accessions and identify 22 accessions that likely carry new sources of resistance.
Technical Abstract: Comparative sequence analysis was used to design a SNP marker that aided in the identification of new sources of oat stem rust resistance. New races of Puccinia graminis f. sp. avenae (Pga) threaten global oat production. An A. strigosa accession known to carry the broadly effective oat stem rust resistance gene, Pg6, was crossed with two susceptible A. strigosa accessions to generate 198 F2:3 families and 190 F5:6 RILs. The RIL population was used to determine that Pg6 was a single dominant gene located between 475 and 491 Mbp on diploid chromosome AA2 of the A. atlantica genome. This region was further refined by identifying SNPs associated with Pg6 resistance in a panel of previously sequenced A-genome accessions. Twenty-four markers were developed from SNPs that showed perfect association between the Pg6 phenotype and 11 sequenced Avena diploid accessions. These markers were validated in the RILs and F2:3 families, and the markers most closely linked with resistance were tested in a diverse panel of 253 accessions consisting of oat stem rust differentials, all available diploid Avena spp. accessions, and 41 A. vaviloviana accessions from the National Small Grains Collection. One SNP marker located at 483, 439, 497 bp on AA2, designated as AA2_483439497, was perfectly associated with the Pg6 phenotype in Avena strigosa diploids and was within several Kb of a resistance gene analog, RPP13. The marker results and seedling testing against Pga races DBD, KBD, TJS, and TQL enabled the postulation of Pg6 and potential new sources of resistance in the Avena panel. These results will be used to infer Pg6 presence in other germplasm collections and breeding programs and can assist with introgression, gene pyramiding, and cloning of Pg6.