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Key message: The widely deployed, oat stem rust resistance gene Pg13 was mapped by linkage analysis and association mapping, and KASP markers were developed for marker-assisted selection in breeding programs. Pg13 is one of the most extensively deployed stem rust resistance genes in North American oat cultivars. Identification of markers tightly linked to this gene will be useful for routine marker-assisted selection, identification of gene pyramids, and retention of the gene in backcrosses and three-way crosses. To this end, high-density linkage maps were constructed in four bi-parental mapping populations using SNP markers identified from 6K oat Infinium iSelect and genotyping-by-sequencing platforms. Additionally, genome-wide associations were identified using two sets of association panels consisting of diverse elite oat lines in one set and landrace accessions in the other. The results showed that Pg13 was located at approximately 67.7 cM on linkage group Mrg18 of the consensus genetic map. The gene co-segregated with the 7C-17A translocation breakpoint and with crown rust resistance gene Pc91. Co-segregating markers with the best prediction accuracy were identified at 67.7–68.5 cM on Mrg18. KASP assays were developed for linked SNP loci for use in oat breeding. [ABSTRACT FROM AUTHOR]

Key message: The candidate gene for the barley Un8 true loose smut resistance gene encodes a deduced protein containing two tandem protein kinase domains. Abstract: In North America, durable resistance against all known isolates of barley true loose smut, caused by the basidiomycete pathogen Ustilago nuda (Jens.) Rostr. ( U. nuda), is under the control of the Un8 resistance gene. Previous genetic studies mapped Un8 to the long arm of chromosome 5 (1HL). Here, a population of 4625 lines segregating for Un8 was used to delimit the Un8 gene to a 0.108 cM interval on chromosome arm 1HL, and assign it to fingerprinted contig 546 of the barley physical map. The minimal tilling path was identified for the Un8 locus using two flanking markers and consisted of two overlapping bacterial artificial chromosomes. One gene located close to a marker co-segregating with Un8 showed high sequence identity to a disease resistance gene containing two kinase domains. Sequence of the candidate gene from the parents of the segregating population, and in an additional 19 barley lines representing a broader spectrum of diversity, showed there was no intron in alleles present in either resistant or susceptible lines, and fifteen amino acid variations unique to the deduced protein sequence in resistant lines differentiated it from the deduced protein sequences in susceptible lines. Some of these variations were present within putative functional domains which may cause a loss of function in the deduced protein sequences within susceptible lines. [ABSTRACT FROM AUTHOR]

Re-examining historical datasets is a proposed use for association mapping (AM) and is particularly valuable when the data describes timeconsuming and/or expensive to measure traits. A collection of 91 elite two-row malting barley (Aordeum vulgare L.) lines entered in the western Canadian Cooperative Two-Row Barley Trials over a 13yr period were analyzed by AM to identify markers associated with seven malting quality traits. A linear mixed-model incorporatirpg population structure and familial relatedness identified 27 diversity array technology (DArT) markers associated with malting quality. These markers will assist selection of parents with complementary allele combinations for future crosses and help identify progeny with the desired alleles. Putative candidate expressed sequence tags (ESTs) responsible for markertrait associations were identified for 19 of the 27 DArT markers and include genes important for seed storage protein accumulation, gibberellinmediated gene expression, seed storage mobilization, and dormancy. Efforts to identify novel variability in these genes may present opportunities to improve malting quality. [ABSTRACT FROM AUTHOR]