1a. Objectives (from AD-416):
1. In cooperation with breeders and geneticists, identify and facilitate the manipulation of genetic variation of end use quality characteristics in western wheat. Specific end-use quality traits to be studied include: kernel texture (sub-objective 1a), starch and non-starch carbohydrates (sub-objective 1b), polyphenol oxidase activity (sub-objective 1c), and overall milling and baking performance of wheat breeding lines (sub-objective 1d). Sub-Objective 1a. Alter wheat kernel hardness characteristics by identifying and incorporating novel puroindoline gene alleles and texture-related QTLs. Sub-Objective 1b. Determine the degree to which manipulation of polysaccharide content and structure can affect the end-use quality characteristics of wheat flour. Sub-Objective 1c. Determine the degree to which the many polyphenol oxidase genes in wheat impact noodle dough color stability. Sub-Objective 1d. Develop wheat cultivars with superior end-use quality characteristics in collaboration with regional wheat breeders and geneticists. 2. Develop, modify, and evaluate technologies and methodologies for measuring wheat kernel characteristics that impact end use functionality. Specific characteristics to be measured include: Kernel texture (sub-objective 2a), arabinoxylan composition (sub-objective 2b), gluten quality (sub-objective 2c) and polyphenol oxidase activity (sub-objective 2d). Sub-Objective 2a. Determine the reliability and performance of an endosperm brick test developed at the WWQL. Sub-Objective 2b. Develop a diagnostic assay for oxidative gelation of arabinoxylans in flour batters using free-radical-induced/peroxidase-mediated oxidative cross-linking. Sub-Objective 2c. Test a recently developed laser-based prototype instrument for measuring gluten strength via SDS-sedimentation (in collaboration with Dr. Rangan Chinnaswamy, GIPSA) Sub-Objective 2d. Modify our existing PPO L-DOPA assay to identify very low levels of grain PPO. 3. Identify and manipulate the biochemical constituents of wheat to improve the nutritional functionality of grain and flour, specifically dietary fiber and antioxidant content.
1b. Approach (from AD-416):
Determine the molecular and genetic basis of wheat grain texture by assessing puroindoline gene structure. Determine the effect of two different hardness alleles on grain texture, milling performance and baking quality. Assess the molecular genetic basis of discoloration in Asian noodles by identifying and characterizing polyphenol oxidase from wheat. Develop or adapt methods to evaluate wheat end-use quality with an emphasis on early generation testing. Employ gene expression measurement technology to identify genes contributing to desirable Asian food characteristics.
3. Progress Report:
This work falls under NP306. Progress was made on all three objectives and their sub-objectives. (1a) Over 1,000 Aegilops tauschii accessions were obtained and several hundred were grown in the greenhouse, nearly all have been haplotyped for the puroindoline genes. (1b) Crosses were made between waxy germplasm and Stephens, MDM and Xerpha; plots were grown at the WSU agronomy farm. (1c) A new family of PPO genes expressed in developing wheat kernels was identified and the three members named PPO-A2, PPO-B2, and PPO-D2. The chromosomal locations of the five PPO genes known to be expressed in the kernel have been determined through genetic mapping. The relative expression levels of these new PPO genes as well as the previously identified PPO-A1 and PPO-D1 genes were measured. (1d) The 2011 harvest breeder sample evaluations were completed. (2a) Research on kernel texture using endosperm bricks was completed. (2b) Bostwick viscosity test was essentially completed and manuscripts were published. (2c) Collaboration with Dr. Chinnaswamy, GIPSA, was completed on our laser-based gluten meter. Our SDS sedimentation instrument was used to analyze wheat samples and showed that the laser-diodes were capturing substantive gluten quality information. (2d) The work on this sub-objective has been temporarily placed on hold. (3) Over 1,000 Regional Nursery samples were obtained in furtherance of an AFRI/NIFA grant; milling and baking tests were completed.
1. Analysis of a unique super soft kernel trait in wheat for baking. ARS scientists in Pullman, Washington, with collaborators at Washington State University characterized the milling and baking characteristics of a unique "super soft" wheat kernel trait. End-use quality and processing of wheat grain are limited by kernel texture. Four sister lines, 2 super soft, 2 normal soft were milled on a laboratory flour mill and baked into cookies and cakes. The super soft trait was associated with high flour yield and high quality cookies, but most notably soft kernel texture. The results demonstrate that this kernel trait could be used to improve soft white winter wheat quality.
2. Blending different wheat flour mill streams affects soft wheat end-product quality. ARS scientists in Pullman, Washington, with a graduate student at Washington State University studied the effects that blending different wheat flour mill streams had on cookie and cake quality, and the relationship to oxidative gelation of batters. Different mill streams have different compositions due to the milling process and this variation can affect end-product quality. Various mill streams from a pilot flour mill were blended, cookies and cakes were baked, and the streams were analyzed for oxidative gelation and batter viscosity, showing that streams with higher content of non-starch polysaccharides reduced cookie quality and contributed to higher batter viscosity. Flour millers can select specific flour mill streams to optimize soft wheat end-product quality.
3. Puroindoline b-2 genes associated with harder wheat grains. Allelic variation in puroindoline b-2 variant genes was examined in relationship to grain traits, yield components and flag leaf size in bread wheat varieties of the Yellow and Huai river valleys of China. An ARS scientist in Pullman, Washington, in cooperation with Henan Agricultural University and Chinese Academy of Agriculture scientists determined the associations between puroindoline b-2 gene allele variants with other grain and agronomic wheat traits. No one knew if there is an association between puroindoline b-2 variant genes (Pinb-B2v) and other wheat traits. Within the soft wheat class, the Pinb-B2v3 allele was associated with harder grain than the v2 allele. The results provide a number of testable hypotheses to see if these associations are cause and effect or simply indicate founder effects of wheat germplasm.
4. Mice prefer soft wheat kernels. An ARS scientist in Pullman, Washington, with collaborators at Washington State University studied the feeding behavior preferences of the house mouse. Factors influencing the feeding behavior and preferences of the house mouse relative to different wheat types is essentially unknown. Several types of wheat grains were provided to individually house mice and daily consumption was determined. Soft wheat kernels were preferred over hard wheat and white kernels appeared to be preferred over red. This research provides the baseline information and methodology for further studies aimed at understanding flavor and other preferences among wheat varieties.
5. Wheat varieties differ in health-related aspects of wheat grain. ARS scientists in Pullman, Washington, and Beltsville, Maryland, with collaborators at the University of Maryland conducted phytochemical analyses and studied the anti-inflamatory and anti-proliferative activities of whole wheat flour. The health-promoting constituents of whole grain wheat (whole wheat flour) are not fully known. Grain of five different wheat varieties was made into whole wheat flour and analyzed for phytochemical composition, as well as anti-inflamatory and anti-proliferative activities. Wheat varieties differed for all traits examined with the hard red spring wheat WestBred 936 having the highest levels of ferulic acid. The results indicate that wheat varieties with higher levels of phenolics and health-promoting constituents can be selected .
6. Five quantitative trait loci identified that improved wheat dough color stability. ARS scientists in Pullman, Washington, in collaboration with a wheat researcher at Washington State University, genetically mapped five genes that are responsible for a defect in wheat end use quality. Polyphenol oxidase (PPO) causes discoloration in some types of products containing wheat flour. This is perceived negatively by consumers, who in general prefer bright products (e.g. noodles) as opposed to those that have turned a dull grey or brown. Recently we have identified three PPO genes that are responsible for 72% of the PPO RNA levels in developing wheat kernels. We have genetically mapped these three genes in addition to two previously characterized PPO genes; they are located on group 2 chromosomes. The PPO1 and PPO2 paralogous genes were found to be approximately 10 centimorgans apart. We now know that favorable PPO alleles can easily be combined to develop varieties with improved quality.
7. A small part of wheat chromosome 5 controls kernel hardness and vitreosity. ARS scientists in Pullman, Washington, analyzed specially prepared genetic lines for kernel hardness and vitreosity. The genetics of wheat kernel hardness and vitreosity are not completely known, yet both traits influence grain quality. Advanced generation sister lines of the variety Alpowa were compared for kernel hardness and vitreosity. A very small portion of chromosome 5 was shown to control both traits. The results show that genes controlling seed development are located at the tip of chromosome 5, and provide a greater understanding of wheat grain quality.
8. An improved method for measuring an important grain constituent. An ARS scientist in Pullman, Washington, with collaborators at Washington State University and the Katholieke University in Belgium evaluated a colorimetric method for arabinoxylans in wheat grain. Arabinoxylans are important non-starch carbohydrates in wheat grain and thus require an accurate means of measurement. A number of method steps were evaluated with the aim of optimizing performance and increasing accuracy. The time of hydrolysis was critical, but the inclusion of glucose was not necessary and phloroglucinol content could be reduced by half. The modifications to this method improve the accuracy of measuring arabinoxylan content of wheat grain.
9. Prevalence of puroindoline b2 genes in Pacific Northwest wheat breeding germplasm pools. ARS scientists in Pullman, Washington, with collaborators at Washington State University, and a scientist with the Chinese Academy of Agricultural Sciences surveyed the puroindoline b2 genes in Pacific Northwest soft white, hard red and hard white wheat breeding germplasm. Puroindoline genes may influence kernel properties and end-use quality. The puroindoline genes were determined among 388 wheat varieties and breeding lines, and evaluated against kernel texture. Specific gene variants were present according to germplasm pool, for example, hard red spring versus hard red winter. There was no association of puroindoline b2 genes with kernel texture variation indicating that this gene does not play a direct role in end-use quality.
Morris, C.F., Anderson, J.A., King, G.E., Bettge, A.D., Garland Campbell, K.A., Fuerst, E.P., Beecher, B.S. 2011. On the occurrence of a unique 'super soft' kernel trait in wheat. Cereal Chemistry. 88:576-583.