Location: Wheat, Sorghum and Forage Research2010 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 derivatives threatens wheat production world-wide. Work was initiated this year to develop Great Plains adapted winter wheat lines with resistance to Ug99. Crosses were obtained between resistant triticale (a man-made hybrid crop formed by combining all the genes of rye and durum wheat) and common wheats in an attempt to transfer resistant genes. Successful deployment of Ug99 resistant wheat will depend on whether newly developed wheat lines contain also resistance to established pathogens. Wheat streak mosaic virus is a perennial problem impacting wheat production in the western Great Plains. Approximately 30 winter wheats adapted to Nebraska, and carrying resistance to wheat streak mosaic virus, a perennial pest in the western Great Plains, were identified as also carrying resistance to Ug99. Preliminary yield testing of these materials will commence in the fall of 2010. Transgenic wheat has yet to be commercially deployed. A thorough knowledge of the effects of genetic transformation on non-targeted traits such as grain yield is necessary. Transgenic wheat lines, derived from three different transgenic events, and engineered to over-express native seed proteins known as glutenins, were evaluated for both agronomic properties and quality traits. Grain yield was lower than in control cultivars, but was equal to that of non-transgenic sister lines. Thus, grain yield was not diminished by the act of transformation, per se. Baking quality was affected, but not equally so by the three events. Additional experimentation could lead to the development of improved wheats for baking via genetic engineering. Improvement in grain yield is the primary breeding goal of all wheat breeding programs in the Great Plains of North America. Periodic evaluation of the rate of genetic gain in grain yield is important, as world population growth remains unchecked. An assessment of recent trends in genetic improvement of wheat yields is vital to determine whether food demands of an ever-growing world population will be met. Data from USDA-coordinated winter wheat regional performance nurseries collected over the time period 1959-2008 were used to estimate genetic gain (loss) in grain yield and other traits in winter wheats adapted to the Great Plains of North America. In both the Southern Regional (SRPN) and Northern Regional Performance Nurseries (NRPN), linear regression revealed significant positive relationships between relative grain yields of advanced breeding lines and calendar year of the nursery trial. Further analyses showed, however, that relative grain yields of Great Plains hard winter wheats may have peaked in the early to mid-1990’s, and further improvement in the genetic potential for grain yield awaits some new technological or biological advance.
1. Genetic improvement in winter wheat grain yield, 1959-2008. Long-term datasets from the USDA-ARS coordinated winter wheat regional nursery program were used by an ARS scientist in Lincoln, NE, to determine the rate of genetic gain in wheat yields since 1959. Over a 50 year time-period, genetic potential for increased grain yield increased at a rate of approximately 1% per year. However, this rate of increase may have peaked in the mid-1990’s. Policy makers will need to consider that further increases in wheat production may depend on more widespread use of advanced production practices, and use of more productive farmland for wheat cultivation.
2. Waxy wheats have starch properties that differ from normal wheat, with lower cooking properties and the ability to enhance shelf-life of baked goods. Development of adapted waxy wheats could expand the demand for Great Plains wheats. ARS scientists at Lincoln, NE placed the hard winter waxy wheat NX04Y2107 under preliminary seed increase for possible release as a cultivar in 2011. A second waxy winter wheat NX05M4180-6 was found to have resistance to multiple leaf rust races in seedling tests, and has demonstrated good field resistance to leaf and stripe rusts, and to barley yellow dwarf virus. NX05MD4180-6 was descended from soft wheat parents, and has awnless heads, strong straw and soft grain texture, traits typically of use in the soft wheat production region of the eastern U.S. NX05MD4180-6 was entered in the 2010 USDA-ARS Eastern Soft Wheat Uniform Nursery to assess its potential for production east of the Mississippi. For the Great Plains region, 56 new waxy wheat breeding lines were field tested for disease resistance and winter hardiness at Mead, NE. The top 25-30 lines, based on grain yield at harvest, will be entered in replicated yield trials in the fall of 2010.
Hansen, L.E., Jackson, D.S., Wehling, R.L., Graybosch, R.A. 2010. Functionality of Chemically Modified Wild-Type, Partial Waxy and Waxy Starches from Tetraploid Wheats. Journal of Cereal Science. Volume 51: 409-414.