Crown rust disease caused by the fungus Puccinia coronata f. sp. avenae (Pca) is a major production constraint of oat in North America, Europe, and Australia. There are over 100 genes effective ...against one or more Pca races, but only a handful of seedling resistance (Pc) genes have been mapped to a known chromosomal location. The goal of the present study was to use linkage mapping to identify the genomic location of the Pc53 gene, and to produce a list of linked SNPs with potential as molecular markers for marker assisted breeding. The Pc53 gene was placed on the linkage group Mrg08 at 82.4 cM using F5-derived recombinant inbred lines (RILs) from a cross between the Pc53 carrier 6-112-1-15 (PI 311624) and the susceptible cultivar Otana. The map location was validated using RILs from a cross between 6-112-1-15 and the Pc50 differential line. Single nucleotide polymorphism marker GMI_ES02_c14533_567 was the closest to Pc53. A major seedling resistance gene 'PcKM' and QTL QcC.Core.08.1, QCr.Core.08.2, QCr.Core.08.3 and QCr.cdl9-12D were previously reported on Mrg08. QPc.Core.08.1 and PcKM were mapped to within 1 cM of Pc53; but previous virulence studies have indicated separate identities. The chromosomal location of Pc53 and SNPs linked with it will facilitate the utilization of Pc53 in oat breeding programs.
Oat crown rust caused by Puccinia coronata f. sp. avenae P. Syd. & Syd (Pca) is a major constraint to oat (Avena sativa L.) production in many parts of the globe. The objectives of this study were to ...locate Pc96 on the oat consensus map and to develop SNP markers linked to Pc96 for use in marker-assisted selection. SNP loci linked to the crown rust resistance gene Pc96 were identified by linkage analysis and PACE assays were developed for marker-assisted selection in breeding programs. Pc96 is a race-specific crown rust resistance gene originating from cultivated oat that has been deployed in North American oat breeding programs. Pc96 was mapped in a recombinant inbred line population (n = 122) developed from a cross between the oat crown rust differential known to carry Pc96 and the differential line carrying Pc54. A single resistance locus was identified on chromosome 7D between 48.3 and 91.2 cM. The resistance locus and linked SNPs were validated in two additional biparental populations, Ajay × Pc96 (F2:3, n = 139) and Pc96 × Kasztan (F2:3, n = 168). Based on all populations, the most probable location of the oat crown rust resistance gene Pc96 on the oat consensus map was on chromosome 7D approximately at 87.3 cM. In the Ajay × Pc96 population, a second unlinked resistance gene was contributed by the Pc96 differential line, which mapped to chromosome 6C at 75.5 cM. A haplotype of nine linked SNPs predicted the absence of Pc96 in a diverse group of 144 oat germplasm. SNPs that are closely linked to the Pc96 gene may be beneficial as PCR-based molecular markers in marker-assisted selection.
Oat crown rust, caused by Puccinia coronata Corda f. sp. avenae Eriks. (Pca), is a major biotic impediment to global oat production. Crown rust resistance has been described in oat diploid species A. ...strigosa accession PI 258731 and resistance from this accession has been successfully introgressed into hexaploid A. sativa germplasm. The current study focuses on 1) mapping the location of QTL containing resistance and evaluating the number of quantitative trait loci (QTL) conditioning resistance in PI 258731; 2) understanding the relationship between the original genomic location in A. strigosa and the location of the introgression in the A. sativa genome; 3) identifying molecular markers tightly linked with PI 258731 resistance loci that could be used for marker assisted selection and detection of this resistance in diverse A. strigosa accessions. To achieve this, A. strigosa accessions, PI 258731 and PI 573582 were crossed to produce 168 F5:6 recombinant inbred lines (RILs) through single seed descent. Parents and RILs were genotyped with the 6K Illumina SNP array which generated 168 segregating SNPs. Seedling reactions to two isolates of Pca (races TTTG, QTRG) were conditioned by two genes (0.6 cM apart) in this population. Linkage mapping placed these two resistant loci to 7.7 (QTRG) to 8 (TTTG) cM region on LG7. Field reaction data was used for QTL analysis and the results of interval mapping (MIM) revealed a major QTL (QPc.FD-AS-AA4) for field resistance. SNP marker assays were developed and tested in 125 diverse A. strigosa accessions that were rated for crown rust resistance in Baton Rouge, LA and Gainesville, FL and as seedlings against races TTTG and QTRG. Our data proposed SNP marker GMI_ES17_c6425_188 as a candidate for use in marker-assisted selection, in addition to the marker GMI_ES02_c37788_255 suggested by Rine's group, which provides an additional tool in facilitating the utilization of this gene in oat breeding programs.
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.
Population structure and genetic architecture of phenotypic traits in oat (Avena sativa L.) remain relatively under-researched compared to other small grain species. This study explores the historic ...context of current elite germplasm, including phenotypic and genetic characterization, with a particular focus on identifying under-utilized areas. A diverse panel of cultivated oat accessions was assembled from the USDA National Small Grains Collection to represent a gene pool relatively unaffected by twentieth century breeding activity and unlikely to have been included in recent molecular studies. The panel was genotyped using an oat iSelect 6K beadchip SNP array. The final dataset included 759 unique individuals and 2,715 polymorphic markers. Some population structure was apparent, with the first three principal components accounting for 38.8% of variation and 73% of individuals belonging to one of three clusters. One cluster with high genetic distinctness appears to have been largely overlooked in twentieth century breeding. Classification and phenotype data provided by the Germplasm Resources Information Network were evaluated for their relationship to population structure. Of the structuring variables evaluated, improvement status (cultivar or landrace) was relatively unimportant, indicating that landraces and cultivars included in the panel were all sampled from a similar underlying population. Instead, lemma color and region of origin showed the strongest explanatory power. An exploratory association mapping study of the panel using a subset of 2,588 mapped markers generated novel indications of genomic regions associated with awn frequency, kernels per spikelet, lemma color, and panicle type. Further results supported previous findings of loci associated with barley yellow dwarf virus tolerance, crown rust (caused by Puccinia coronata f. sp. avenae) resistance, days to anthesis, and growth habit (winter/spring). In addition, two novel loci were identified for crown rust resistance.
Seed vigor is crucial for crop early establishment in the field and is particularly important for forage crop production. Oat (
L.) is a nutritious food crop and also a valuable forage crop. However, ...little is known about the genetics of seed vigor in oats. To investigate seed vigor-related traits and their genetic architecture in oats, we developed an easy-to-implement image-based phenotyping pipeline and applied it to 650 elite oat lines from the Collaborative Oat Research Enterprise (CORE). Root number, root surface area, and shoot length were measured in two replicates. Variables such as growth rate were derived. Using a genome-wide association (GWA) approach, we identified 34 and 16 unique loci associated with root traits and shoot traits, respectively, which corresponded to 41 and 16 unique SNPs at a false discovery rate < 0.1. Nine root-associated loci were organized into four sets of homeologous regions, while nine shoot-associated loci were organized into three sets of homeologous regions. The context sequences of five trait-associated markers matched to the sequences of rice,
and maize (E-value < 10
), including three markers matched to known gene models with potential involvement in seed vigor. These were a glucuronosyltransferase, a mitochondrial carrier protein domain containing protein, and an iron-sulfur cluster protein. This study presents the first GWA study on oat seed vigor and data of this study can provide guidelines and foundation for further investigations.
Kernel shape and β‐glucan content are important attributes for oat (Avena sativa L.) millers. The identification of genomic regions controlling these traits, as well as their effect on phenotype, ...will enable rapid gain from selection. The objectives of this study were (a) to identify the genomic regions associated with kernel shape in an oat panel adapted to subtropical environments and (b) to clarify the relationship between kernel shape and β‐glucan content in oat. An elite oat panel comprising 406 inbred lines was assessed in Londrina and Eldorado do Sul, Southern Brazil. Genome‐wide association analyses were performed for each environment separately and also in a multi‐environment analysis. Phenotypic and genetic correlation coefficients were estimated between kernel shape traits and β‐glucan content. Genomic regions influencing kernel length were identified on Mrg06, Mrg21, and Mrg24. Kernel width and kernel thickness were genetically correlated and shared a quantitative trait locus, located on Mrg13 of the oat consensus map. Phenotypic and genetic correlations were found between kernel shape traits and β‐glucan content, indicating a negative relationship between kernel width or kernel thickness and β‐glucan content. Oat breeding programs that aim to maintain minimum levels of β‐glucan for nutrition and minimum kernel widths for milling will need to screen for both traits; otherwise, indirect selection will lead to unfavorable results. However, the negative correlation was not too strong (–0.4), suggesting that improvement for both traits can be made simultaneously.
Core Ideas
Variation in multiple genomic regions controls kernel shape traits in oat.
Markers associated with variation in kernel length are located on Mrg06, Mrg21, and Mrg24.
Kernel width and kernel thickness are correlated; both are influenced by variation on Mrg13.
Kernel width and kernel thickness are negatively correlated with β‐glucan content.
Selection of wider and thicker kernels may decrease oat β‐glucan content.
Most oat grains destined for human consumption must possess the ability to pass through an industrial de-hulling process with minimal breakage and waste. Uniform grain size and a high groat to hull ...ratio are desirable traits related to milling performance. The purpose of this study was to characterize the genetic architecture of traits related to milling quality by identifying quantitative trait loci (QTL) contributing to variation among a diverse collection of elite and foundational spring oat lines important to North American oat breeding programs. A total of 501 lines from the Collaborative Oat Research Enterprise (CORE) panel were evaluated for genome-wide association with 6 key milling traits. Traits were evaluated in 13 location years. Associations for 36,315 markers were evaluated for trait means across and within location years, as well as trait variance across location years, which was used to assess trait stability. Fifty-seven QTL influencing one or more of the milling quality related traits were identified, with fourteen QTL mapped influencing mean and variance across location years. The most prominent QTL was Qkernel.CORE.4D on chromosome 4D at approximately 212 cM, which influenced the mean levels of all traits. QTL were identified that influenced trait variance but not mean, trait mean only and both.
Developing improved barley (Hordeum vulgare L.) germplasm with resistance to barley stripe rust (BSR) has been a goal of several breeding programs since the introduction of this disease into the ...Americas. The USDA–ARS two‐rowed spring malting barley breeding line 95SR316A, while susceptible at the seedling stage, has field resistance to BSR. This study was conducted to identify markers useful for marker‐assisted selection for resistance to BSR. This line was used as a parent in two biparental mapping populations: 95SR316A × ‘Lenetah’ (susceptible), and 95SR316A × ‘Grannelose Zwiezelige’ (GZ; seedling resistance). Progeny were observed for response to BSR infection in the field at four location–years per population. Disease severity was taken as the percentage of leaf area infected. The 95SR316A × GZ (F5–derived recombinant inbred line RIL) and 95SR316A × Lenetah (doubled haploid) populations were genotyped using Illumina's 50K barley array. Interval mapping revealed quantitative trait loci (QTL) in both populations on chromosome 2H (Qpsh.316A.2Ha) near the p‐terminal, with the allele derived from 95SR316A contributing to lower disease severity. In addition, the 95SR316A × GZ population was segregating for a QTL on chromosome 2H (Qpsh.316A.2Hb) at ∼35 cM with effects on BSR observed in two location years. The 95SR316A × Lenetah population was segregating for Qpsh.316A.7H at 94.04 cM on chromosome 7H with peak logarithm of the odds (LOD) scores of 25.81, 36.75, and 5.35 observed in Corvallis, OR, in 2018, Davis, CA, in 2018, and Mt. Vernon, WA, in 2018, respectively. The QTL on chromosomes 3H, 5H, and 6H were observed in only single location–years in the 95SR316A × Lenetah population.
Accessions of cultivated oat (Avena sativa L.) from the United States Department of Agriculture-Agricultural Research Service Small Grains Collection in Aberdeen, ID were characterized for adult ...plant resistance (APR) and seedling resistance to crown rust, caused by Puccinia coronata f. sp. avenae. Initially, 607 oat accessions with diverse geographic origins were evaluated in field tests in Baton Rouge, LA. Of those, 97 accessions were not fully susceptible and were tested in the field in St. Paul, MN against a diverse P. coronata f. sp. avenae population. Thirty-six accessions that had some level of resistance in both field tests and mean coefficients of infection of ≤20 were further evaluated for APR and seedling resistance. Among these, four accessions (PI 193040, PI 194201, PI 237090, and PI 247930) were resistant to eight P. coronata f. sp. avenae races as seedlings. Twenty-nine accessions had resistance to at least one of the P. coronata f. sp. avenae races. Three accessions (CIav 2272, CIav 3390, and PI 285583) were fully susceptible to all eight P. coronata f. sp. avenae races as seedlings. Further evaluation of the three seedling-susceptible accessions at the flag leaf stage in a growth chamber resulted in moderately susceptible to moderately resistant responses. The resistance sources presented here may contain genes not deployed in elite oat varieties, and may be useful for future crown rust resistance breeding. The adult and seedling resistance found in accessions of the cultivated oat species is especially valuable because it avoids problems associated with the transfer of genes from wild species to cultivated oat.
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