A ‘Langdon’ durum wheat line with a pair of 6B chromosomes from an accession of Triticum turgidum L. var. dicoccoides (Körn. in litt., in Schweinf.) Bowden [LDN(DIC‐6B)] previously was shown to have a gene(s) for high grain protein content (GPC). The objectives of this study were to develop a mapping population segregating only for genes on chromosome 6B, map the gene(s) for high GPC, and identify closely linked markers for use in marker‐assisted breeding for this trait. The 6B mapping population was grown in replicated field trials and evaluated for GPC. A restriction fragment length polymorphism (RFLP) map of this population was available. The quantitative trait locus (QTL) analyses provided strong evidence that a gene(s) for high GPC (named QGpc.ndsu‐6Bb) is located near the centromere of 6B. The most likely location for the gene(s) is in the short arm between Xabg387‐6B and Xmwg79‐6B. The logarithm of the odds (LOD) score for this interval is 18.9. Segregation in this segment accounted for 66% of the variation in GPC. Eleven additional markers have been mapped within 7 centimorgans (cM) of the midpoint of Xabg387‐6B and Xmwg79‐6B. One or more of these markers should be useful in marker‐assisted breeding for high GPC in dorum wheat.

Kernel morphology and texture influence the value of wheat (Triticum aestivum L.). The objectives of this study were to determine associations between kernel traits and molecular markers and to identify quantitative trait loci (QTLs) affecting kernel traits in a soft × hard white wheat cross. Seventy eight F~-derived recombinant inbred lines (RILs) from cross be tween the so ft wh ite wh eat NY 6432-18 (NY18) and the hard white wheat 'Clark's Cream' (CC) were developed by single seed descent. Kernel texture was measured by near infrared reflectance (NIR) on RIL grain samples from six environments. Digital image analysis (DIA) was used to measure kernel length, width, area, perimeter on grain samples from four environments. Test weight and thousand kernel weight (TKW) were also determined. Shape factor and density factor were calculated. The map for this population consisted of 313 molecular markers in 47 linkage groups located on all wheat homoeologous chromosome groups. Linkage groups that mapped to wheat homoeologous group 2 chromosomes were highly skewed towards NY18 alleles. Genotype effects and genotype × environment interactions were highly significant for most traits. QTLs for kernel width and kernel length also influenced kernel area and TKW, but did not influence each other. The pinB marker at the puroindoline B locus on chromosome 5DS explained over 60% of the phenotypic variation for kernel texture. QTLs for kernel traits were located on chromosomes IA, 2B, 2D, 3B, 7A, and 7B. Tm HE ECONOMIC VALUE of the U.S. wheat crop is deterined by class, which depends in part on kernel morphology and texture, and by test weight. Inspectors for the U.S. Grain Inspection, Packers and Stockyards Administration use color, shape, and length of the kernel and shape of the germ, crease, and brush to determine wheat grain classes (GIPSA, 1997). In general, hard wheat kernels are long, narrow, and translucent while soft kernels are short, rounded, and chalky in appearance. Hybridization between classes reduces the correlation between kernel morphology and wheat class and reduces the accuracy of the current classification

Cereal Chem. 86(4):463-469The objective of this study was to investigate whether a narrow-bore column (NBC) (300 × 4.5 mm, i.d.) improved analyses of unreduced proteins in flour by size-exclusion HPLC (SE-HPLC) and subsequent evaluation of breadmaking quality of hard spring wheat flours. Total protein extracts and SDS buffer extractable and unextractable proteins were analyzed by SE-HPLC. NBC separated proteins in 10 min at a flow rate of 0.5 mL/min with similar resolution to a regular column (300 × 7.8 mm, i.d.) which took 30 min. SE-HPLC absorbance area (AA) data ob-tained from an NBC showed comparable or superior repeatability and correlations with flour breadmaking characteristics when compared with those of a regular column. AA values of total protein that were calculated by adding AA values of SDS extractable and unextractable proteins showed greater repeatability and correlations with quality characteristics than those of actual total protein extracts. The improvements including employment of an NBC in SE-HPLC provide enhancement of rapid quality evaluation and decreased consumption of hazardous organic solvents.

Kernel characteristics, particularly kernel weight, kernel size, and grain protein content, are important components of grain yield and quality in wheat. Development of high performing wheat cultivars, with high grain yield and quality, is a major focus in wheat breeding programs worldwide. Here, we report chromosome regions harboring genes that influence kernel weight, kernel diameter, kernel size distribution, grain protein content, and grain yield in hard red spring wheat breeding lines adapted to the Upper Midwest region of the United States. A genetic linkage map composed of 531 SSR and DArT marker loci spanned a distance of 2,505 cM, covering all 21 chromosomes of wheat. Stable QTL clusters influencing kernel weight, kernel diameter, and kernel size distribution were identified on chromosomes 2A, 5B, and 7A. Phenotypic variation explained by individual QTL at these clusters varied from 5 to 20% depending on the trait. A QTL region on chromosome 2B confers an undesirable pleiotropic effect or a repulsion linkage between grain yield (LOD = 6.7; R (2) = 18%) and grain protein content (LOD = 6.2; R (2) = 13.3%). However, several grain protein and grain yield QTL independent of each other were also identified. Because some of the QTL identified in this study were consistent across environments, DNA markers will provide an opportunity for increasing the frequency of desirable alleles through marker-assisted selection.