Location: Wheat, Sorghum and Forage Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Identify and develop winter wheat germplasm having novel quality traits, including modified starch composition, enhanced gluten strength, and enhanced mineral element concentration. Sub-objective 1.A.: Identify waxy wheats with grain yield equal in magnitude and stability to that of current wheat cultivars. Sub-objective 1.B.: Develop new waxy wheat breeding lines for germplasm and cultivar release. Sub-objective 1.C.: Develop winter wheats with elevated grain protein content and elevated Fe, Zn and available P concentrations via genetics and breeding. Objective 2: Determine the effects of altered grain composition on gluten extraction from waxy wheat and the effects of the absence of grain polyphenol oxidase on flour quality. Sub-objective 2.A.: Determine the factors governing the efficiency of gluten extraction from waxy wheats. Sub-objective 2.B.: Determine the relationship between super-low (nil) grain polyphenol oxidase (PPO) and product quality; determine the environmental stability of the nil PPO trait. Sub-objective 2.C.: Develop adapted hard white winter wheat germplasm with nil levels of grain PPO. Objective 3: Identify and develop winter wheat germplasm having resistance to wheat streak mosaic virus, stem rust, and pre-harvest sprouting. Sub-objective 3.A.: Pyramid genes for resistance to stem rust and Wheat streak mosaic virus with genes conditioning quality traits, including nil PPO and tolerance to pre-harvest sprouting. Sub-objective 3.B.: Identify, evaluate and exploit sources of tolerance to pre-harvest sprouting. Sub-objective 3.C.: Coordinate the Hard Winter Wheat Regional Nursery Program and use the nurseries to: 1) determine the yield potential and stability of newly developed hard winter wheat germplasm, and 2) distribute germplasm to Great Plains breeding programs.
1b. Approach (from AD-416):
The project will combine classical breeding with the modern genetic tools of transformation and DNA marker technology to develop wheat germplasm and cultivars with traits of economic importance. Multi-location field trials will be used to assess the stability of advanced waxy wheat breeding lines relative to those of the most commonly grown current NE and SD cultivars. The project also will expand the selection of waxy wheat cultivars via breeding and selection. Cereal chemistry techniques will be used to determine the relationships between gluten extraction of waxy wheat and easily scored classical indicators of gluten strength, the mixograph, and high-molecular-weight (HMW) glutenin composition, and to determine if over-expressed HMW glutenin subunits can improve gluten extraction efficiencies. Recombinant inbred lines will be used to determine whether, in the presence of low phytate mutants, the high protein gene GPC-B1 can be used to simultaneously elevate grain protein, Fe and Zn concentrations, and whether such effects result in pleiotropic effects on grain yield. This project will alleviate deficiencies in the current hard white wheat gene pool by developing wheats with low levels of grain polyphenol oxidase, tolerance to pre-harvest sprouting, and resistance to wheat stem rust and Wheat streak mosaic virus. Genes for these traits will be pyramided using traditional mating approaches, and fixed in resultant germplasm via direct phenotypic selection, and DNA marker evaluations.
3. Progress Report:
Commercial-scale testing of a waxy (amylose-free starch) wheat developed by this project is underway. In anticipation of the need for additional waxy wheat cultivars, fifty experimental waxy wheat breeding lines were developed and tested in multi-location yield trials in Nebraska and South Dakota. Glutenin protein composition also was determined, and the information will be used to predict the efficiency of gluten extraction from waxy wheats. To develop even more improved waxy wheat germplasm, approximately 60 new matings were conducted between ARS-developed hard waxy winter wheats, and adapted Great Plains materials. From existing breeding materials, a new, high-yielding waxy wheat line, NX11MD2337, was identified. NX11MD2337 carries field resistance to wheat leaf and stem rusts, and is tolerant of stripe rust and Hessian fly. It will be entered in regional yield trials in the fall of 2014. Grain polyphenol oxidase (PPO) activity causes discoloration of wheat food products. A gene conditioning the near-absence of PPO, designated “nil PPO”, was transferred by traditional breeding methods to more adapted genetic backgrounds. Materials selected after this first round of matings were field-grown at Yuma, AZ, for quality evaluations. From a second cycle of matings, several dozen lines with the nil PPO trait were isolated and used as parents in a third cycle of mating. Materials derived from this third cycle will form the basis of future efforts to develop adapted nil PPO germplasm and cultivars. Nutritional quality of wheat has been often overlooked in favor of investigations on wheat processing quality. An experiment is underway to address this topic. The GPC-B1 gene conditioning elevated grain protein content and increased iron and zinc contents was combined with the low grain phytate trait, also correlated with elevated grain iron and zinc. Inbred lines were selected from early generation populations that survived the Nebraska winters. Despite rather divergent genetic backgrounds of the parents, fairly well-adapted materials were identified. Both export and domestic markets are interested in the development of hard white winter wheats. Such wheats require both low levels of grain polyphenol oxidase, and tolerance to pre-harvest sprouting. Production of white wheats in the target environment, the western Great Plains, is limited by diseases such as Wheat streak mosaic virus, and wheat stem rust. A new mating scheme was initiated to combine genes for the above-mentioned nil PPO trait, with those conditioning tolerance to pre-harvest sprouting, resistance to Wheat streak mosaic virus and resistance to domestic and exotic races of wheat stem rust. Over 200 crosses were obtained between parents donating at least two of these traits. From existing, advanced generation breeding trials, two new, high-yielding lines with resistance to Wheat streak mosaic virus conditioned by the Wsm-2 gene, were identified and moved to advanced regional trials. Both are also resistant to North American races of wheat stem rust.