1a. Objectives (from AD-416)
Investigate the genetic mechanisms by which the plant hormones abscisic acid (ABA) and gibberellin (GA) control pre-harvest sprouting stand establishment, and drought and cold tolerance in wheat and model organisms. Develop and utilize molecular markers for the western region wheat and barley breeding programs for resistance to stem rust, other biotic and abiotic stresses, and end-use quality. Develop wheat cultivars with durable resistance to stripe rust, stem rust, soilborne diseases, cold and drought, and improved end-use quality for Western Region cropping systems using wheat germplasm resources from the USDA-ARS National Small Grains Germplasm Collection (NSGC) and other national and international sources.
1b. Approach (from AD-416)
Determine whether ABA sensitivity controls grain dormancy and tolerance to preharvest sprouting. Determine whether degree of drought tolerance and cold tolerance tend to correlate with each other and depend upon ABA sensitivity. Determine how GA signaling controls seed dormancy and plant height. Identify and use new and existing molecular markers linked to genes for biotic stress resistance, specifically for stripe rust resistance. Identify and use new molecular markers for genes linked to abiotic and end-user quality. Establish and use high-throughput molecular marker analysis systems to track the segregation of important genes in wheat and barley breeding programs. Characterize core wheat germplasm sets for use in identifying haplotypes important in Western Regional germplasm adaptation. Use molecular markers to link genotypes to phenotypes while maintaining critical haplotypes for enhancement, disease resistance and end-use quality in Western Region wheat breeding programs. Identify new sources of genes giving superior end-use quality, disease resistance, and resistance to cold and drought. FY09 Program increase. Add 0.00 SY.
3. Progress Report
Objective 1 discovered that increased ABA hormone sensitivity in wheat results in increased grain dormancy and drought tolerance. These lines appear to use water more efficiently based on stomatal closure and carbon-isotope discrimination measurements over 3 field seasons. Objective 1C examined the role of the plant hormone GA in controlling plant height and seed germination in the model plant Arabidopsis. Research showing that DELLA RGA is controlled by protein-protein interaction with the GA receptor GID1 is relevant to wheat seedling emergence and lodging. GA control of seed germination is needed to control preharvest sprouting and stand establishment. GID1 can deactivate the germination-specific DELLA protein RGL2. The effect of GID1 is similar after-ripening suggesting these processes may share underlying mechanisms. To examine this in wheat, we have raised a polyclonal antibody to wheat DELLA Rht1. For Objective 2, the genotyping lab advanced the development of new molecular markers by identifying and evaluating new markers for leaf rust Lr34 and Lr57/Yr40, photoperiod response, late maturing alpha amylase, stem and stripe rust disease resistance genes. The lab optimized and screened molecular markers for disease resistance genes including Fusarium Head Blight, Hessian Fly, Septoria Tritici Blotch, and Strawbreaker Root Rot, stripe and stem rust resistance. The majority of disease screens were for rust resistance. Quality traits screened included Glutenins, protein, puroindolines, pasta color, falling number and PPO genes. Agronomic characteristics included vernalization, height, photoperiod response, and drought tolerance markers. In this current fiscal year 107,928 datapoints were submitted to the genotyping laboratory, currently 107,928 datapoints have been analyzed. To characterize core wheat germplasm for Western adaptation, we have collected over 600 breeding lines from the breeders in MT, OR, CA, ID, and WA. DNA has been isolated, and over 12,768 datapoints have been analyzed. For Objective 3 new wheat germplasm adapted to the Western region has been developed. Cara club wheat is available for growers to plant in 2009. A soft white winter ARS960277L and club wheat, ARS97075-3C, both with resistance to leaf and soilborne disease, increased yield, and improved quality were identified for breeder seed increase. These cultivars will reduce grower risk due to disease, cold, drought, as well as improve the quality of wheat. Crosses were made between adapted cultivars and diverse international germplasm that possess resistance to Fusarium crown rot and lesion nematodes, two soil borne diseases. Molecular markers for resistance to eyespot, BYDV, preharvest sprouting and hessian fly traits were used to select lines within 7,117 progeny. Markers for eyespot, stripe rust, and stem rust disease resistance, glutenins, height, and photoperiod response were assessed on 670 advanced lines. Use of high throughput molecular marker systems to select progeny increases the efficiency of field based trait analysis because only those lines with favorable alleles are re-tested.
1. Floral transformation of wheat. Current methods for wheat transformation involve the use of tissue culture which is expensive and sometimes causes undesirable changes or "somaclonal variation" in the wheat variety being transformed. A technique was developed by ARS scientists in Pullman, WA that allows wheat transformation by dunking opened flowers/spiklets in Agrobacterium media. Experiments using this method demonstrated transformation of wheat with a gene that turned the grains red. This research provides a new method for wheat transformation that can be used to efficiently translate knowledge about cloned genes into crop improvement.
2. Development of new wheat cultivars with resistance to multiple diseases that will enhance the quality of the wheat export crop. The question examined was whether genomic based laboratory selection methods could be combined with greenhouse and field based selection methods to develop new wheat cultivars that met production, disease resistance, and quality targets for the western wheat crop. ARS scientists in Pullman, WA used marker assisted selection for resistance to eyespot and stripe rust, combined with greenhouse and field based evaluation for disease resistance and grain production traits, as well as laboratory based quality analysis to develop three new wheat cultivars. Cara club wheat has been increased and seed will be available to growers in the fall of 2009 while ARS960277L soft white winter wheat and ARs97075-3C club wheat will undergo initial seed increase in the fall of 2009. All three of these cultivars meet the highest quality standards for the western soft wheat and club wheat crop and are agronomically competitive with current wheat cultivars, and since they require no fungicide for disease control. They will reduce chemical input and provide greater profits for growers.
3. Reliable molecular markers for stripe rust resistance genes in wheat. The question examined was whether reliable and efficient molecular markers could be identified and used to select among segregating progeny for stripe rust resistance. ARS scientists in Pullman, WA used genetic linkage and QTL analysis to identify a simple sequence repeat marker linked to a strong gene for adult plant resistance in the spring wheat cultivar ‘Louise’ and we developed new molecular maps and identified the best molecular markers to use for two seedling resistance genes. All three of these markers were assayed on progeny in the breeding program. This research provides a fast way of combining multiple genes for stripe rust resistance into new cultivars.
4. Hormonal control of drought tolerance in wheat. The question examined was whether wheat plants with increased sensitivity to the plant hormone ABA will show increased drought tolerance. Warm (wheat ABA-responsive mutants) were identified and planted at two locations in the field in WA by ARS scientists in Pullman as well as in the greenhouse, transpiration was assessed on well watered and water-stress plants and monitored via a leaf promoter and infrared camera. The mutants showed increased transpiration efficiency in the field and appeared to have increased drought tolerance in greenhouse drought experiments. This research provides wheat germplasm that can be grown in drier places and consume less water while producing similar grain yields.
5. How plants grow. The question examined was whether the plant hormone Gibberelin (GA) can down-regulate the DELLA repressors of plant growth in the absence of DELLA-protein destruction. ARS researchers in Pullman, WA showed that DELLA-repression of plant growth can be lifted by the GA receptor GID1 leading to growth of taller plants in Arabidopsis. This research disproves the previous theory that DELLA-repression can be lifted only by protein destruction. The research thus provides a new method for fine control of crop plant height.
6. Resistance to Rhizoctonia Root Rot in wheat. The question examined was whether wheat genetic variants with resistance to the root disease caused by Rhizoctontia could be identified using chemicals to increase genetic variability. No genetic resistance to Rhizoctonia was previously known in wheat. The method identified by ARS scientists in Pullman, WA showed a tolerant line called Scarlet-Rz1. This line could possibly result in decreased yield loss in dry farming regions.
Zale, J., Agarwal, S., Loar, S., Steber, C.M. 2008. Floral Transformation of Wheat, Chapter 6, pp. 105-113. IN: Huw D. Jones and Peter R. Shewry (eds.) Methods in Molecular Biology, Transgenic Wheat, Barley and Oats. Humana Press, New York, NY.