Location: Hard Winter Wheat Genetics Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Develop adapted hard red or white wheat germplasm lines with improved resistance to emerging or intractable problems in wheat production and marketing. Objective 2: Increase understanding of the molecular basis of parasite virulence, host resistance, and stress tolerance for these problems. Objective 3: Develop and apply phenotypic and genotypic selection technology for these traits to hard red or white winter wheat germplasm or cultivar development.
1b. Approach (from AD-416):
Production of high quality hard red or white winter wheat is limited by recurring intractable problems such as leaf rust, Fusarium head blight, Hessian fly, and heat stress during the grain filling period. In addition, new emerging problems such as stripe rust, stem rust, and Karnal bunt threaten the production or marketing of high quality grain. The first objective of this project is to develop adapted hard red or white wheat germplasm lines with improved resistance or tolerance to these problems. We will utilize existing sources and identify new sources of resistance, introgress them into desirable backgrounds, and then release them for use as parents of commercial cultivars. The second objective is to increase our understanding of the molecular basis of parasite virulence, host resistance, and stress tolerance to support strategic development and deployment of genetic resistance. Greater understanding of secreted virulence/avirulence effectors in the Hessian fly and the leaf rust pathogen may lead to better strategies for durability. Greater understanding of the mechanisms of durable rust resistance and heat tolerance may lead to discovery of new genes or alleles with complementary mechanisms and to optimized gene combinations in new cultivars. The third objective is to develop and apply phenotypic and genotypic selection technology for these traits to hard red or white winter wheat germplasm and cultivar development. This is an essential component of the technology transfer effort. Large-scale phenotypic screening data for Hessian fly and Karnal bunt resistance and genotypic marker data will be provided to cooperators.
3. Progress Report:
1) More than 13,000 wheat breeding samples from 14 public breeding programs and 2 private breeding programs were analyzed for molecular markers in the USDA-ARS Hard Winter Wheat Regional Genotyping Laboratory. We also analyzed three regional wheat nurseries with 50 specific markers linked to important traits of interest to breeders. A total of over 300,000 marker data points were generated in 2012. The data were used by wheat researchers for selecting wheat breeding lines. 2) More than 4,700 wheat lines from 11 wheat breeding and genetics programs and 4 regional nurseries or performance tests were screened in the greenhouse for resistance to the Hessian fly. Results were sent to breeders to aid in the selection of elite lines. In some cases, resistant lines were selected, dug up, and were shipped back to the breeders. 3) Approximately 4,100 lines were scored for resistance to wheat stripe rust in an irrigated screening nursery at Rossville, KS in 2011/2012. The nursery included three mapping populations, four regional nurseries or performance tests, and entries from nine wheat breeding programs. Data on disease reactions were used to assist in selection of breeding lines and for mapping the locations of resistance genes for stripe rust. 4) An irrigated stem rust field screening nursery was conducted in 2012. A mapping population for minor gene resistance to stem rust was scored for resistance reactions. These data will be used next year to map the locations of the resistance genes. A fungicide efficacy test was also conducted for stem rust in collaboration with KSU researchers. 5) This was the second year of work under specific cooperative agreements with six public wheat breeding programs to introgress resistance to Ug99 stem rust into elite adapted wheat cultivars. Each breeding program made crosses between resistant donor lines and their own elite breeding lines. The primary goal is to produce new varieties with three-gene or four-gene combinations of resistance genes Sr22, Sr26, Sr35, and Lr34. 6) A core collection of 1414 diverse winter wheat lines from the National Small Grains Collection in Aberdeen, ID was assessed for adult plant resistance to leaf rust in the greenhouse, and at Castroville, TX, and Hutchinson, KS. An association mapping panel of hard winter wheat with a total of 304 lines was also assessed at the same locations. 7) In 2012, a much improved second assembly of the Puccinia triticina genome was developed in collaboration with the Broad Institute. The genomic sequence is being used to identify important genes in the pathogen that control virulence and avirulence. 8) An association mapping strategy was used to identify wheat genes for aluminum tolerance in a panel of hard and soft winter wheat cultivars. The mapping population consisted of 380 germplasm lines from the USA, Asia and several other countries that were collected, purified, and analyzed with 300 simple sequence repeat DNA markers and 9000 single nucleotide polymorphism DNA markers.
1. New wheat germplasm released with resistance to Ug99 stem rust from wild wheatgrass. Wheat stem rust has become a serious threat to wheat production due to the emergence of new highly virulent races in Africa, known collectively as the Ug99 group. In collaboration with Kansas State University, ARS researchers in Manhattan, KS and St. Paul, MN released the wheat germplasm line KS13WGGRC60, which carries wheat stem rust resistance gene Sr44. Sr44 is effective against the Ug99 group. Sr44 was derived from the wild wheatgrass species, Thinopyrum intermedium, and is now available as a balanced compensating translocation whereby the short arm of chromosome 7J of T. intermedium is attached to the long arm of wheat chromosome 7D. This germplasm line can be used in developing new resistant wheat varieties.
2. Four new wheat cultivars co-developed by ARS and universities. New wheat cultivars are needed by producers to maintain and increase yields. In collaboration with Colorado State University and Oklahoma State University, ARS researchers in Manhattan, KS and St. Paul, MN participated in the development and registration of four new wheat cultivars for the Great Plains. ARS researchers selected the varieties for resistance to rust diseases, Hessian fly, and grain quality using a combination of traditional and molecular marker techniques. These new high yielding cultivars are now available for wheat producers.
3. Development of genomic selection, a new wheat breeding technique. Genomic selection is a new statistical approach that allows plant breeders to select the best breeding lines based on genome-wide DNA (molecular) markers. ARS Researchers in Manhattan, KS and Ithaca, NY, in collaboration with Cornell University, showed how next-generation sequencing can be applied to a wheat breeding program to produce robust, yet inexpensive, DNA markers in an approach called “genotyping-by-sequencing” (GBS). GBS is an excellent tool for breeding purposes and DNA markers can be discovered simultaneously with assaying the whole population of interest. GBS markers can also be used to predict the performance of breeding lines for grain yield, heading date, and thousand kernel weight. The low per-sample cost of GBS will enable widespread application of genomic selection in breeding programs. This will lead to increasing the rate of genetic gain and more rapid development of new cultivars.
4. Genes for resistance to Fusarium head blight identified in two wheat varieties. Fusarium head blight is a destructive disease of wheat worldwide. Genetic resistance is the main method of controlling this disease. The Chinese wheat landrace Huangfangzhu has a high level of resistance to FHB. The Kansas wheat cultivar Heyne has a moderate level of resistance. ARS researchers in Manhattan, KS identified a total of eight resistance genes in the two varieties. Molecular markers were identified for each gene. These genes and markers can be used for improving resistance to Fusarium head blight in U.S. wheat varieties.
5. Rapid mobilization of lipids may be key to host plant resistance to Hessian fly of wheat. Resistance is the most effective way to control Hessian fly, an important pest of wheat. However, resistance in current wheat cultivars is short-lived, usually lasting for only 6-8 years. To develop more durable resistant wheat varieties, we need a better understanding of the resistance mechanisms at the molecular level. ARS researchers in Manhattan, KS discovered that there was rapid mobilization of membrane lipids in resistant plants following Hessian fly attack. The mobilized membrane lipids were apparently converted into defense-related products such as polyunsaturated free fatty acids, oxylipins, and components of cuticle wax. Our results suggest that rapid mobilization of membrane lipids may constitute an important step in wheat defense against Hessian fly attack. This research provides a foundation for future research on the role of lipids in wheat resistance to Hessian fly.
6. Molecular markers identified for Soil-borne wheat mosaic virus (SBWMV). SBWMV can cause significant yield losses of winter wheat and resistance is a high priority in many breeding programs. However, the disease occurs inconsistently and it is difficult to select for resistance in the field. ARS researchers in Manhattan, KS, in collaboration with Oklahoma State University, used association analysis to identify one major gene for SBWMV resistance on the long arm of chromosome 5D. In addition, a gene on the short arm of chromosome 4D was also associated with disease resistance. Markers linked to the two genes should be useful in marker-assisted selection in U.S. winter wheat.
Zhang, D., Bai, G., Hunger, R., Bockus, W., Yu, J., Carver, B., Brown Guedira, G.L. 2011. Association study of resistance to soil-borne wheat mosaic virus (SBWMV) in U.S. winter wheat. Phytopathology. 101:1322-1329.