Michael S. McMullen

Staling of Bread as Affected by Waxy Wheat Flour Blends

ABSTRACT Crumb softness and improved shelf life of bread is often achieved by incorporating expensive shortenings in the formulation. We hypothesized that similar results could be achieved by blending bread wheat flour with waxy (low amylose) durum wheat flour. White pan bread was baked from 10, 20, and 30% waxy durum wheat flour composites and evaluated for loaf volume and crumb firmness over a period of 0, 3, and 5 days. The loaf volumes were not affected by the waxy flour blends. However, as staling progressed over 3–5 days, significant firming of crumb was observed in the control sample compared with loaves containing waxy flour. The firmness was inversely proportional to the level of waxy flour used in the blend. A 20% waxy wheat flour blend was optimal in retarding staling while producing bread quality comparable with the control. It was further established that bread made with 20% waxy flour gave lower firmness values after 5 days of storage in comparison to bread made with 3% shortening. These res...

SNP Discovery and Chromosome Anchoring Provide the First Physically-Anchored Hexaploid Oat Map and Reveal Synteny with Model Species

A physically anchored consensus map is foundational to modern genomics research; however, construction of such a map in oat (Avena sativa L., 2n = 6x = 42) has been hindered by the size and complexity of the genome, the scarcity of robust molecular markers, and the lack of aneuploid stocks. Resources developed in this study include a modified SNP discovery method for complex genomes, a diverse set of oat SNP markers, and a novel chromosome-deficient SNP anchoring strategy. These resources were applied to build the first complete, physically-anchored consensus map of hexaploid oat. Approximately 11,000 high-confidence in silico SNPs were discovered based on nine million inter-varietal sequence reads of genomic and cDNA origin. GoldenGate genotyping of 3,072 SNP assays yielded 1,311 robust markers, of which 985 were mapped in 390 recombinant-inbred lines from six bi-parental mapping populations ranging in size from 49 to 97 progeny. The consensus map included 985 SNPs and 68 previously-published markers, resolving 21 linkage groups with a total map distance of 1,838.8 cM. Consensus linkage groups were assigned to 21 chromosomes using SNP deletion analysis of chromosome-deficient monosomic hybrid stocks. Alignments with sequenced genomes of rice and Brachypodium provide evidence for extensive conservation of genomic regions, and renewed encouragement for orthology-based genomic discovery in this important hexaploid species. These results also provide a framework for high-resolution genetic analysis in oat, and a model for marker development and map construction in other species with complex genomes and limited resources.

Genotypic and environmental effects on oat milling characteristics and groat hardness.

ABSTRACT The production of oat bran involves the dehulling of oats, inactivation of their enzymes, and the subsequent grinding and sieving of the clean groats to isolate the larger bran particles. The bran yield from the oat groats may be related to their hardness, as it is in wheat. Groat breakage, which occurs during the dehulling process, reduces milling yield and may also be related to groat hardness. This study sought to investigate genotypic and environmental effects on oat dry milling and oat dehulling characteristics, and attempted to define properties associated with oat groat hardness. Significant genotypic differences in bran yield were largely attributed to groat composition, where higher β-glucan and oil concentrations in the groat were associated with higher bran yields. Bran composition was largely dependent on a combination of the bran yield and the groat composition. Although groat breakage was correlated with bran yield and with groat β-glucan concentration, environmental factors appeare...

Quality of Spaghetti Made from Full and Partial Waxy Durum Wheat

ABSTRACT The waxy character is achieved in durum wheat (Triticum turgidum L. var. durum) when the granule-bound starch synthase activity is eliminated. The result is a crop that produces kernels with no amylose in the starch. The presence of two Waxy loci in tetraploid wheat permits the production of two partial waxy wheat genotypes. Advanced full and partial waxy durum wheat genotypes were used to study the effect of waxy null alleles on pasta quality. Semolina from full and partial waxy durum wheats was processed into spaghetti with a semicommercial-scale extruder, and pasta quality was evaluated. Cooked waxy pasta was softer and exhibited more cooking loss than pasta made from traditional durum cultivars. These features were attributed to lower setback of waxy starch as measured with the Rapid Visco Analyser. High cooking loss may be due to the lack of amylose-protein interaction, preventing the formation of a strong protein network and permitting exudates to escape. Waxy pasta cooked faster but was le...

Starch Characteristics of Waxy and Nonwaxy Tetraploid (Triticum turgidum L. var. durum) Wheats

ABSTRACT Manufacture of pasta products is paramount for durum wheat (Triticum turgidum L. var. durum). The recent development of waxy durum wheat containing starch with essentially 100% amylopectin may provide new food processing applications and present opportunities for value-added crop production. This investigation was conducted to determine differences in some chemical and functional properties of waxy durum starch. Starch was isolated from two waxy endosperm lines and four nonwaxy cultivars of durum wheat. One of the waxy lines (WX-1) was a full waxy durum wheat whereas the other line (WX-0) was heterogeneous, producing both waxy and nonwaxy seed. Effects on starch swelling, solubility, pasting, gelatinization, and retrogradation were examined. The full waxy starch had four times more swelling power than the nonwaxy durum starches at 95°C, and was also more soluble at three of the four temperatures used. Starch pasting occurred earlier and peak viscosities were greater for starches from both waxy li...

Optimizing Conditions for Experimental Oat Dehulling

ABSTRACT The determination of groat percentage in experimental oat breeding lines requires the dehulling of oats. Here, we report the results of our efforts to optimize dehulling conditions so that the most accurate and reliable result can be obtained. Hand dehulling was always reliable and accurate, however, it was the most time-consuming and tedious of the methods studied. Two mechanical methods of oat dehulling, compressed-air dehulling and impact dehulling, also frequently provided reliable results, however, results were strongly influenced by dehulling conditions. Optimal dehulling conditions represented compromises between unfavorable extremes. Correct aspiration strength was critical to accurate groat percentage determination. We have found that a secondary aspiration is highly desirable after compressed-air dehulling to remove hulls remaining with the groats after dehulling. Also, increased mechanical stress on oats as exerted either by the number of passes through the impact dehuller, or by the a...

Association of Avenanthramide Concentration in Oat (Avena sativa L.) Grain with Crown Rust Incidence and Genetic Resistance

ABSTRACT Avenanthramides (avn) are antioxidant compounds found in oat tissues, including the grain, that are of interest from a nutritional standpoint. In this study, we have measured avenanthramide concentration in the grain of 18 oat genotypes grown in six environments. These genotypes varied widely in crown rust (Puccinia coronata) resistance. Crown rust infected two of the six environments studied. The grain avenanthramide concentrations in the crown rust environments were significantly higher than those in the uninfected environments. Avenanthramide concentrations in the crown rust infected environments was also significantly correlated with their genetic crown rust resistance, as evaluated in the field. These results suggest that avenanthramide accumulation in the grain is associated with crown rust infection and that, in most of the cultivars evaluated, the extent of their accumulation also correlated with their genetic disease resistance; avenanthramide accumulation in the grain was, with noted ex...

Grain quality characteristics and milling performance of full and partial waxy durum lines

ABSTRACT Mutation of the gene coding for the granule bound starch synthase (waxy protein) leads to reduced amylose content in cereal endosperm. Durum wheat (Triticum turgidum L. var. durum) has one waxy locus in each of its two genomes. Full waxy durum wheat is produced when both genomes carry the waxy null alleles. When only one locus is mutated, partial waxy durum wheat is obtained. Partial and full waxy near-isogenic lines of durum wheat developed by a breeding program were analyzed as to their quality characteristics. Amylose was largely eliminated in full waxy lines; however, no reduction in amylose content was detected in partial waxy lines. The waxy mutation did not affect grain yield, kernel size, or kernel hardness. Full waxy durum lines had higher kernel ash content, α-amylase activity, and a unique nonvitreous kernel appearance. Protein quality, as evaluated by SDS microsedimentation value, gluten index, and wet gluten was slightly lower in the full waxy lines than in the other genotypes. Howev...

Sources of Variation in Oat Kernel Size

ABSTRACT Oat kernel size uniformity is important to the oat milling industry because of the size fractionations that occur in the milling process. We measured frequency of single, double, and triple kernel spikelets and kernel mass of primary, secondary, and tertiary kernels from each spikelet type (for a total of six kernel types) to determine relative influence of kernel type, panicle position, genotype, and environment on oat kernel size for 10 oat cultivars grown at four locations. Kernel type was the most important factor affecting kernel size. Primary kernels from triple kernel spikelets were larger than primary kernels from double kernel spikelets. Tertiary kernels were the smallest. Environments that produced larger kernels also produced higher frequencies of triple kernel spikelets. Some genotypes produced no triple kernel spikelets in any environment, whereas others produced varying proportions, depending on the environment. Kernels closer to the top of the panicle were larger than those near th...

Population Genomics Related to Adaptation in Elite Oat Germplasm

An oat association‐mapping panel contributed by active breeding programs worldwide. Characterized population structure and found subdivisions related to adaptation Characterized genome‐wide and chromosome‐specific linkage disequilibrium Performed association‐mapping and post hoc modeling of heading date Found several consistently associated QTL