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Variation for wheat (Triticum aestivum L.) grain yield and agronomic traits was used to map quantitative trait loci (QTL) in a 'Cheyenne' (CNN) × [CNN ('Wichita' 3A)] recombinant inbred chromosome line (RICL) population consisting of 223 CNN(RICL53A) and 7 check cultivars that were evaluated in six environments in Nebraska during 2005-2007. A chromosome 3A linkage map spanning 106 cM was constructed using 32 microsatellite markers. Composite interval mapping detected 19 QTL for seven agronomic traits that individually accounted for 4.6 to 16.8% of the phenotypic variation. Three small genomic segments, spanning 3.4, 5.3, and 5.3 cM, contained most of the QTL. Two yield QTL were detected in two environments and in data pooled over environments. For grain volume weight, a QTL was detected in five of the six environments while a plant height QTL was detected in all environments. Wichita (WI) alleles contributed to the increased trait values for yield, spikes per square meter, and grain volume weight, while CNN contributed alleles to the increased 1000-kernel weight, plant height, and anthesis date. Both CNN and WI contained alleles for increased number of kernels per spike. The 223 CNN(RICLs3A) set had greater power to detect QTL than the two smaller subsets-128 CNN(RICLs3A) developed using doubled haploids and 95 CNN(RICLs3A) developed using recombinant monosomic lines. Neither of the subsets performed consistently better than the other in detecting QTL. [ABSTRACT FROM AUTHOR]

Genetic diversity is the basis for successful crop improvement and can be estimated by different methods. The objectives of this study were to estimate the genetic diversity of 30 ancestral to modern hard red winter wheat ( Triticum aestivum L.) cultivars adapted to the Northern Great Plains using pedigree information, morphological traits (agronomic measurements from six environments), end-use quality traits (micro-quality assays on 50 g grain or milled flour samples for the six environments), and molecular markers (seed storage proteins separated using SDS-PAGE, 51 SSRs, and 23 SRAP DNA markers), and to determine the relationships of genetic distance estimates obtained from these methods. Relationships among diversity estimates were determined using simple (Pearson) and rank (Spearman) correlation coefficients between distance estimates and by clustering cultivars using genetic-distances for different traits. All methods found a wide range in genetic diversity. The genetic distance estimates based on pedigree had the highest values due to possible over-estimation arising from model assumptions. The genetic diversity estimates based on seed storage protein were lowest because they were the major determinants of end-use quality, which is a highly selected trait. In general, the diversity estimates from each of the methods were positively correlated at a low level with the exceptions of SRAP diversity estimates being independent of morphologic traits (simple correlation), SDS-PAGE, and SSR diversity estimates (rank correlation). However, SSR markers, thought to be among the most efficient markers for estimating genetic diversity, were most highly correlated with seed storage proteins. The procedures used to accurately estimate genetic diversity will depend largely upon the tools available to the researcher and their application to the breeding scheme. [ABSTRACT FROM AUTHOR]

Evaluation of wheat cultivars from different eras allows breeders to determine changes in agronomic and end-use quality characteristics associated with grain yield and end-use quality improvement over time. The objective of this research was to examine the trends in agronomic and end-use quality characteristics of hard red winter wheat cultivars grown in Nebraska. Thirty historically important and popular hard red winter wheat cultivars introduced or released between 1874 and 2000 were evaluated at Lincoln, Mead and North Platte, Nebraska in 2002 and 2003. An alpha lattice design with 15 incomplete blocks of two plots and three replications was used at all locations. Agronomic (days to flowering, plant height, spike length, culm length, grain yield and yield components, and grain volume weight) and end-use quality (flour yield, SDS-sedimentation value, flour protein content, and mixograph time and tolerance) traits were measured in each environment. Highly significant differences were observed among environments, genotypes and their interactions for most agronomic and end-use quality characteristics. Unlike modern cultivars, older cultivars were low yielding, and less responsive to favorable environments for grain yield and yield components. Semidwarf cultivars were more stable for plant height than traditional medium to tall cultivars. All cultivars had high grain volume weight since it is part of the grading system and highly selected for in cultivar release. Modern cultivars were less stable than older cultivars for SDS-sedimentation and mixing tolerance. However, the stability of older cultivars was attributed to their having weak mixing tolerance and reduced SDS-sedimentation values. The reduced protein content of modern cultivars was offset by increased functionality, as measured by mixograph and SDS sedimentation. In conclusion, breeders have tailored agronomic and end-use quality traits essential for hard red winter wheat production and marketing in Nebraska. [ABSTRACT FROM AUTHOR]

Chromosome doubling is critical for obtaining doubled-haploid plants from wheat (Triticum aestivum L.) anther culture. The most common doubling method applies colchicine to the plant. However, colchicine is phytotoxic and can induce a high frequency of plant death. In this experiment, anthers from two wheat genotypes ('Pavon 76' and 'Centurk') were placed on nine embryoid initiation media having three sugar sources (maltose, sucrose, and maltose + glucose) with three colchicine concentrations (0.0, 0.1, and 0.2 g 1[SUP-1]. Wheat starch was used as a gelling agent. After three days, the anthers were washed and moved to fresh media without coichicine. Increasing the colchicine concentration decreased the number of embryoids produced from 77.4 embryoids/100 anthers to 29.9 embryoids/100 anthers, but did not significantly affect the frequency of plant regeneration (0.49 green plants/embryoid to 0.40 green plants/embryoid), and increased the frequency of doubled-haploid plants (19.0 doubled-haploid plants/100 green plants to 72.3 doubled-haploid plants/100 green plants). Considering the total number of doubled-haploid plants produced, low levels of colchicine added to the initiation media were very effective. [ABSTRACT FROM AUTHOR]

Sugars are critical components in bread wheat (Triticum aestivum L.) anther culture media for successful somatic embryo initiation and plant regeneration. In this experiment, anthers from three wheat genotypes were cultured on a modified Liang's 85D12 initiation medium with seven sugar combinations (I-sugars: galactose, mannose, maltose, fructose, sucrose, glucose, maltose + glucose) at 0.26 M, and 2,4-dichlorophenoxyacetic acid (2 mg/L), 1-naphthalene acetic acid (1 mg/L), and glutamine (254 mg/L). Wheat starch (5 % W/V), a potential source of sugars, was used as the medium gelling agent. No previous research has studied the effect of different sugars with wheat starch. A split-plot experimental design with 42 replications was used with genotypes as whole plots and sugar combinations as subplots. Galactose and mannose did not support embryoid initiation and were dropped from the analysis. Averaged over the three genotypes, maltose was the best sugar (105 embryoids/100 anthers), followed by glucose (47 embryoids/100 anthers) and maltose + glucose (37 embryoids/100 anthers). These three sugar combinations were superior to the standard medium sugar, sucrose (24 embryoids/100 anthers), and to fructose (12 embryoids/100 anthers). The embryoids were divided into two groups for plant regeneration. The first group was transferred to regeneration medium (Liang 85D12 salts, sugars at 0.06 M, and wheat starch at 7 % w/v as gelling agent) with the same sugar (R-sugar) used as in initiation. The second group was transferred to regeneration media with sucrose. I+R-maltose (0.55) and R-sucrose with I-maltose + glucose (0.48) produced the highest numbers of green plants per embryoid. In general, R-sucrose was a very effective sugar for plant regeneration. The highest frequency of albino plants per embryoid (0.15) occurred on glucose medium. I+R-maltose + glucose and I+R- maltose induced the highest frequency of spontaneous doubling (27.5 %). [ABSTRACT FROM AUTHOR]