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Inbred cultivars and advanced breeding lines have been subjected to numerous recombination cycles, have strong allelic selection for desired traits, and share important attributes for adaptation and agronomic performance. Genetic variation in elite gene pools captured using molecular markers is immediately useful for cultivar development. The primary goal of this study was to implement a genome‐wide association study for 17 agronomic traits using elite inbred lines. A panel consisting of 237 elite hard red spring wheat (Triticum aestivum L.) lines from different wheat breeding institutions in North America were evaluated in 11 locations over 2 yr. A total of 19,192 polymorphic single‐nucleotide polymorphism (SNP) markers from the Illumina 90K SNP array and markers linked to major genes controlling plant height, photoperiod sensitivity, and vernalization were used to assay the population. Linkage disequilibrium was observed to decay within a map distance of ∼3 cM in the A and B genomes and 7 cM in the D genome. A total of 226 marker‐trait associations were identified. Potentially novel associations were detected for grain yield on chromosome 2B and kernels per spike on 1B and 7D, whereas others colocalized with well‐known adaptation loci for photoperiod response, vernalization, and plant height. The frequency of positive alleles for specific marker‐trait associations differed among the programs, suggesting targets for introgression by the respective breeding programs.

While imidazolinone herbicides are an attractive alternative for weed control, spring wheat (Triticum aestivum L.) is susceptible to most of these herbicides. Three mutant alleles conferring resistance to the imidazolinone herbicides were previously identified in spring wheat following seed mutagenesis, but little is known about the physiological and molecular basis of resistance conferred by these alleles. On the basis of acetohydroxyacid synthase (AHAS; E.C. 4.1.3.18) assays, imazethapyr resistance in genotypes TealIMI 10A (AhasL-D1), TealIMI 11A (AhasL-B1), TealIMI 15A, and BW755 (AhasL-D1) was due to a herbicide resistant form of AHAS. TealIMI 15A, which is homozygous for two resistance alleles, was the most resistant at the enzyme level, suggesting resistance in wheat is additive. Nucleotide sequence analysis of clones derived from susceptible cultivar CDC Teal and resistant lines indicated the presence of three genes coding for the catalytic subunit of AHAS. Using a collection of T. aestivum cv. Chinese Spring aneuploid and deletion lines, ahasL-D1, ahasL-B1, and ahasL-A1 mapped to the long arm of chromosomes 6D, 6B, and 6A, respectively. Comparison of partial AhasL-D1, and AhasL-B1 deduced amino acid allele sequences with wild-type sequences indicated resistance was due to a Ser-Asn substitution near the carboxyl terminal of resulting AHAS catalytic subunits. This substitution was not present on the single isolated clone of AhasL-A1 from TealIMI 15A. This is the first report of the molecular characterization of the AHAS gene family from wheat., ACETOHYDROXYACID SYNTHASE, also known as acetolactate synthase (ALS), is a key enzyme in the biosynthesis of the branched chain amino acids valine, leucine, and isoleucine in eukaryotes and prokaryotes (Singh, [...]

Our group previously reported five quantitative trait loci (QTL) associated with plant height, test weight, thousand-kernel weight, and grain protein content in a recombinant inbred line population derived from spring wheat (Triticum aestivum L.) cultivars ‘Attila’ and ‘CDC Go’, evaluated across three environments (2008–2010) under organic management and genotyped with 579 diversity arrays technology and Rht-B1 markers. No QTL was identified for flowering time, maturity, grain yield, and number of tillers across all three environments. In the present study, we reanalyzed the same phenotypic data with a subset of 1200 informative single-nucleotide polymorphic (SNP) markers out of the 90K SNP array and three gene-specific markers (Ppd-D1, Vrn-A1, and Rht-B1) to investigate if high marker density improves QTL detection. Here, five moderate- and eleven minor-effect QTLs were detected across all three organic environments using the new genotypic data, including 13 QTLs that were not previously detected. Up to five QTLs were detected for each trait, except grain protein content, which individually accounted for 5.5 to 18.8% of phenotypic variance. For each trait, the total phenotypic and genetic variance explained by all detected QTLs varied from 9.3 to 39.4 and from 24.6 to 96.8%, respectively, which was much greater than in our previous study. One of the moderate-effect QTLs on 5A was coincidental for flowering time and maturity and mapped close to the Vrn-A1 gene, while the second moderate-effect coincidental QTL on 4B was associated with both plant height and maturity but was 27 cM from the Rht-B1 gene. Results from this study provide additional information for wheat researchers and organic wheat breeders. [ABSTRACT FROM AUTHOR]

Breeding efforts have been important in addressing the challenges of wheat production in western Canada. We studied the effect of breeding on grain yield and other important traits of 100 wheat cultivars released in Canada from 1885 to 2012. The cultivars were grown in seven environments during 2011 to 2013. Grain yield was positively correlated with days to maturity and kernel weight but negatively correlated with plant height, lodging, and grain protein content. Results indicate that grain yield increased at a rate of 0.28% year-1 in 62 cultivars of Canada western red spring (CWRS) class, 1.2% year-1 in 9 cultivars of Canada prairie spring (CPS) class, but not in 14 studied cultivars of Canada western amber durum (CWAD) class due to breeding efforts. Grain protein content exhibited an increasing trend in cultivars of CWRS (0.05% year-1) and CPS (0.79% year-1) classes, and a decreasing trend in those of CWAD (0.23% year-1). Days to maturity decreased in CWRS (0.02% year-1) and CWAD (0.09% year-1) classes but remained unchanged in CPS class. Plant height exhibited a gradual decline in cultivars of CWRS (0.16% year-1) and CWAD class (0.44% year-1), but an increase in those of CPS class (0.50% year-1). Test weights showed an increasing trend in CWRS (0.04% year-1) and CPS (0.17% year-1) classes but not in CWAD class. Grain weight also increased over time in CWRS (0.06% year-1) and in CPS (0.41% year-1), but not in CWAD class. These results suggest that breeding efforts have improved yield, quality and other attributes in wheat cultivars of different Canadian wheat classes over the last 100 years. [ABSTRACT FROM AUTHOR]