1a. Objectives (from AD-416)
The long-term objective of this project is to provide wheat, barley, and sorghum producers with new pest resistant crops and technologies that will protect their crops from insect pests. Over the next 5 years we will focus on the following objectives: 1: Discover new sources of genetic resistance to insect pests (Russian wheat aphid, greenbug, and bird cherry-oat aphid) in wheat, barley, sorghum, and related species; 2: Determine genetic control of resistance, genetic diversity of resistance, and characterize genetic mechanisms of resistance to insect pests in wheat, barley, and sorghum; and 3: Develop wheat, barley, and sorghum germplasm/varieties with resistance to insect pests, increased yield, and other value-added traits.
1b. Approach (from AD-416)
To accomplish the research objectives, the project will search available germplasm collections to find new, effective sources of resistance to virulent aphid pests. The genetic diversity and genetic control of resistance will be characterized, and resistance genes will be transferred into adapted genetic backgrounds. Plant genotyping will be conducted to map aphid resistance genes to the crop chromosomes and to develop molecular markers for marker-assisted selection. The research team of the project will work closely with collaborating plant breeding programs to obtain elite breeding lines to use as parents in backcrossing procedures to transfer aphid resistance and other value-added (enhanced ethanol production) traits. The genetically improved germplasm will be field-tested for agronomic and quality performance prior to release. The project will provide testing and selecting support to assure these desirable genes move through the various breeding programs on their way to the producers via cultivar and hybrid releases.
3. Progress Report
Purification of greenbug resistant germplasm lines: It is normally assumed that all individual seeds in a germplasm accession (collection) are not genetically uniform because most plant germplasm were simply collected from unpurified seed sources of land races or genetically variable populations. Therefore, the newly identified sorghum germplasm resistant to greenbug must be purified in order to obtain genetically uniform seeds. All the individuals showing resistance to greenbug during the screening process are being selfed and subject to progeny testing and selection using the pure-line selection procedure. The selection process will be continued until they become genetically uniform in phenotype, which may take a few generations. At present, pure-line selection of all resistant germplasm sources is underway. (NP301, Component 3C) Evaluation and selection of barley lines: Crosses and backcrosses were made to transfer the hulless trait into high yielding, dual aphid-resistant, 6-rowed, winter hulled barley germplasm lines, as well as to develop genetic populations for future inheritance and genetic diversity studies. DNA was sampled from 200 F2 plants for a molecular mapping study. One thousand advanced breeding lines were grown and harvested in the greenhouse for a cooperating USDA-ARS barley breeder. Replicated yield trials of 75 parental lines were conducted at 3 field locations in Oklahoma. Head selections were made from 130 F2 populations. Data was collected from 900 plants to validate a new BCOA screening technique. (NP301, Component 3C) Developing a sorghum mapping population: An immortalized F2 population is being developed using the selected parent lines. One parent has strong resistance to greenbug, and the other one is the model line BTx623, susceptible to greenbug. This mapping population containing more than 400 progeny will facilitate sorghum genotyping research and has the potential to develop a saturated QTL map with highly dense molecular markers. (NP301, Component 2C)