Location: Wheat, Sorghum and Forage Research2011 Annual Report
1a. Objectives (from AD-416)
1. Develop winter wheats adapted to the Great Plains with novel starches for use in biofuel production and in food product manufacturing. Improve gluten strength and extractability of such wheats to produce a more economically viable package for producers and end-users. 2. Develop hard white winter wheat germplasm with tolerance to pre-harvest sprouting and with nil levels of grain polyphenol oxidase (PPO). 3. Coordinate the Hard Winter Wheat Regional Nursery Program to facilitate the evaluation, distribution, and exchange of high-yielding, high-quality, disease- and pest-resistant hard winter wheats for Great Plains environments. Develop and disseminate winter wheats with resistance to Ug99 and other cereal rusts.
1b. Approach (from AD-416)
Winter wheats with waxy (amylose-free) starch suitable for cultivation in the Great Plains and the Pacific Northwest will be developed via intermatings with adapted types and recurrent selection. Fermentation assays will be used to determine the most suitable starch composition for conversion of wheat grain and starch to ethanol. Transgenic wheats over-expressing native high-molecular-weight glutenin proteins will be tested as a means of overcoming the technical problem of low gluten extraction from waxy wheats. Hard white wheat germplasm with tolerance to pre-harvest sprouting will be identified by use of controlled environment studies, and molecular markers. Hard red winter wheat lines capable of serving as donors of genes for resistance to pre-harvest sprouting in white wheats will be identified after diallel matings. Hard white winter and spring wheat germplasm, with nil levels of grain polyphenol oxidase, will be identified after intermatings of non-adapted donor lines, and adapted materials. Field and laboratory studies will be used to evaluate the environmental stability of the trait and identify molecular markers linked to the trait.
3. Progress Report
The evolution of wheat stem rust race Ug99 and its derivatives threatens world wheat production. Progress was made this year in developing Great Plains adapted winter wheat lines with resistance to Ug99. Successful deployment of Ug99 resistant wheat by farmers will depend on whether newly developed wheat lines contain resistance to established pathogens. Wheat streak mosaic virus is a perennial problem impacting wheat production in the western Great Plains. Wheat lines carrying resistance to Wheat streak mosaic virus were mated to several different sources of Ug99 resistance. Over 400 advanced breeding lines that potentially combine both resistance to Wheat streak mosaic virus and an unknown Ug99 resistance gene were derived. Agronomic testing and additional disease screening will commence in the fall of 2011. In the future, these various approaches will allow wheat lines with both stem rust and virus resistance to be delivered to Great Plains wheat growers. Nutritionists have long urged the American public to consume more whole grain products. To assist in this goal, hard white winter wheat has been developed as an alternative market class in the Great Plains. Market penetration, documented by grocery store sales of whole wheat bread made from white wheats, has been phenomenal. Many hard white winter wheats lack some essential quality characteristics desired both by domestic and overseas users of hard white wheat. These traits include tolerance to pre-harvest sprouting and low levels of the grain enzyme polyphenol oxidase. Pre-harvest sprouting occurs in wet harvest years, and results in both loss of functional quality and seed germination. This year, over 30 new hard white winter wheats with tolerance to pre-harvest sprouting were identified. The top seven performing lines, in terms of agronomic performance and disease resistance, were identified. These lines will be entered in advanced or preliminary USDA-ARS coordinated winter wheat performance nurseries, where they will be available to Great Plains wheat breeding programs. Red wheats are more tolerant to pre-harvest sprouting than white wheats, but variation exists amongst them for the level of tolerance. Red wheat must be used to breed new white wheats, as little adapted white wheat germplasm is available. A study was conducted to identify red wheats capable of donating genes for tolerance to pre-harvest sprouting, independent of the genes conditioning red grain color. The red wheats Jagalene, Niobrara, and NE98466 were ranked highest. Polyphenol oxidase is responsible for discoloration during storage and cooking. Wheats from Australia were found to carry mutations that eliminate grain polyphenol oxidase. The process of introducing these genes to adapted winter wheats was initiated. Over 75 breeding populations were created, and will be seeded in the fall of 2011 to recover winter-hardy selections with the desired nil polyphenol oxidase trait. A genetic study was conducted, and it was determined that one of the Australian parents used likely carries a new, previously uncharacterized gene that eliminates polyphenol oxidase from the grain.
1. Retardation of staling in fresh baked bread. Staling of bread is an age-old problem in the baking industry. ARS scientists at Lincoln, NE, in collaboration with Kansas State University, demonstrated that small amounts of waxy wheat flour substituted for typical flour resulted in greater loaf volumes and in softer fresh bread immediately after baking. This effect was observed, however, only in the first few days after baking. New flours formulated with addition of waxy wheat could, therefore, be developed for the fresh-baked goods market, with accruement of significant financial savings in terms of reduction of losses due to staling.
2. Enhanced protein quality via genetic engineering. High temperatures during development of wheat seeds or grain can result in a loss of protein quality. Protein quality, often termed gluten strength, is absolutely essential for modern large-scale bakeries, and for whole grain bread production. Elevation of certain key grain proteins, designated glutenin subunits, via genetic engineering, has been used in the past in the hope of alleviating temperature-induced loss of gluten strength. Most past experiments resulted either in little effect, or an effect that was too dramatic for practical application. ARS scientists at Lincoln, NE, Albany, CA and Manhattan, KS identified one introduced gene in the seed - as capable of providing enhanced dough strength, but still at commercially useful levels. This study suggests that manipulation of the wheat genome will be useful in offsetting imminent declines in wheat protein quality due to global warming.
3. Reducing product loss in wheat. Evaluation of germplasm maintained at the USDA-ARS National Small Grain Collection in Aberdeen, ID by ARS scientists working at Lincoln, NE, resulted in the identification of accessions from Australia that carry natural mutations that eliminate wheat grain polyphenol oxidase, an enzyme involved in product loss due to discoloration. Wheat carries multiple genes encoding grain polyphenol oxidase, but genetic studies revealed that strains of wheat with these newly discovered mutant genes at one specific genetic locus have the lowest activity. This trait was evident even when plants were infected by a bacterial disease. ARS researchers used these natural mutant strains of wheat to create other strains with virtually undetectable level of polyphenol oxidase enzyme activity. These new genetic strains are being used in NE, CO and MT wheat breeding programs to improve wheat quality and profitability for American farmers.
Baenziger, P.S., Graybosch, R.A., Nelson, L.A., Regassa, T., Klein, R.N., Baltensperger, D.D., Santra, D., Ibrahim, A., Chen, M., Bai, G. 2011. Registration of 'NH03614 CL' Wheat. Journal of Plant Registrations. 5:75-80.