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:
Identification of new sources of aphid resistance in barley: 166 barley cultivars were screened to BCOA via a new greenhouse seedling screening technique for the identification of BCOA resistance. There were no survivors. These same cultivars plus all lines previously identified to have some level of resistance were screened in the spring and survivors rescued and increased in the greenhouse for future purification. 177 accessions from the NSGC were screened with RWA1. The first year of an economic injury level trial was conducted in CO to determine the level of field resistance. Studies of genetic control of aphid resistance: Crosses were made and genetic populations developed to determine genetic diversity in 8 sources of GB resistant barley. These included traditional genetic populations and mapping populations. Inheritance of RWA resistance in 1 barley line was determined. Transfer aphid resistance and other value added-traits into barely breeding lines: The hulless trait was transferred into superior dual aphid-resistant germplasm lines. Heads were selected from 120 F2 populations, and 2,457 hulless heads were screened for RWA and GB resistance. Over 4,000 F3 were increased. Over 3,600 RWA/GB-resistant hulless F4 lines were evaluated for agronomics in the field, and remnant seed screened to determine homozygosity of RWA and GB resistance. A yield trial of 99 RWA/GB-resistant, hulless and hulled, winter barley lines was conducted. This included a hulled line with Rsg2 GB resistance. A RWA-resistant winter barley was grown in large-scale plots for seed increase prior to cultivar release. Heads were sampled to verify purity of resistance. Assessment of genetic and phenotypic diversity of a core collection of sorghum: Genetic diversity and relationship among 64 biofuel sorghum accessions was assessed using AFLP markers in combination with phenotypic evaluation of bioenergy related traits, including height, grain production and total biomass. A total of 802 polymorphic bands were produced across 63 accessions from four AFLP primer combinations, ranging from 32 to 275 bands per combination, which showed they have very diverse genetic background. Developing and advancing sorghum breeding populations: The GB-resistant pedigree was advanced further, and the segregating populations were screened to identify the most productive genotypes with resistance to greenbug. Development and advancement of sorghum cold-tolerant populations: Sorghum cold-tolerant populations were developed from a cross between the elite line BTx623 and a cold tolerant landrace from China. Then pedigrees have advanced to the F3 generation. A method for evaluating seedling cold tolerance in temperature-controlled growth chamber was developed. Development of new crosses: Five new crosses were made between selected elite lines and the donor parents with desired traits for developing high-performance sorghum crop. Collaborative efforts: Screened the Northern and Southern Regional Performance Nurseries with RWA. These wheat lines came from 15 universities/institutions. 300 lines of wheat were increased in the greenhouse in cooperation with Oklahoma State University.
1. Association mapping of Russian wheat aphid resistance genes in barley. Russian wheat aphid is a newly introduced, serious pest that yearly threatens wheat and barley production in the western US. At the time of its introduction, all US barley cultivars were susceptible to this pest. Out of the entire National Small Grains Collection of unadapted accessions only 109 had some level of resistance. How many unique genes were actually represented by these 109 was not clear. In order to not waste time and effort breeding germplasm lines that were redundant (had the same genes for resistance) it is helpful to know which lines most likely carry unique genes and concentrate on developing and deploying germplasm and cultivars with the most diversity for resistance. This association mapping study, performed by ARS researchers in Stillwater, Oklahoma; Aberdeen, Idaho, and Fargo, North Dakota, identified 9 major genes involved in RWA resistance and indicated which resistant lines should be targeted in breeding programs to best protect US barley against Russian wheat aphid attack.
2. Gene identification in preferred lignocellulosic biomass sorghum. Sorghum is one of the most competitive bioenergy crops for biomass production. However, converting biomass to ethanol is currently far too expensive to be commercially competitive because removing lignin from biomass is a very costly step in the ethanol conversion process. Our recent study identified differentially expressed genes in brown mid-rib (bmr) sorghum mutants using a complementary approach combining suppression subtractive cDNA library and cDNA microarray expression profiling. Then expression of the genes associated with the reduction of lignin production in bmr sorghum was characterized at the molecular level, which contributes a better knowledge of which genes are involved in lignin biosynthesis and how these genes are regulated. Furthermore, these newly identified candidate genes offer the new resources for genetic improvement of biomass digestibility, leading to effective conversion of biomass to bioenthanol at a low cost.
Mornhinweg, D.W., Bregitzer, P.P., Porter, D.R., Peairs, F.R., Baltensperger, D.D., Hein, G.L., Randolph, T.A., Koch, M., Walker, T. 2012. Registration of 'Stoneham' spring feed barley resistant to Russian wheat aphid. Journal of Plant Registrations. 6(1):1-5.
Zhang, F., Ping, J., Du, Z., Cheng, Q., Huang, Y. 2011. Identification of a new race of Sporisorium reilianum and characterization of the reaction of sorghum lines to four races of the head smut pathogen. Journal of Phytopathology. 159:342-346.
Srinivas, G., Huang, Y., Carver, B.F., Mornhinweg, D.W. 2012. AFLP genetic diversity analysis in Russian wheat aphid resistant wheat accessions. Euphytica. 185(1):27-15.
Dahleen, L.S., Bregitzer, P.P., Jackson, E.W., Mornhinweg, D.W. 2012. Association mapping of russian wheat aphid resistance in barley as a method to identify diversity in the National Small Grains Collection. Crop Science. 52:1651-1662.