Location: Small Grains and Potato Germplasm Research
2020 Annual Report
Objectives
The long-term objective of this project is to maintain and enhance NSGC as a worldwide resource of small grains germplasm for the research community. Specifically, during the next five years we will focus on the following objectives. Objective 1. Efficiently and effectively acquire genetic resources of small grains and their wild relatives; maintain their safety, genetic integrity, health and viability; and distribute them and associated information worldwide. 1A. Acquire crop wild relatives of wheat, barley, rice, and oat that are under-represented by taxonomy or geography and other threatened small grains germplasm. 1B. Maintain and back-up NSGC accessions. 1C. Regenerate NSGC accessions on a continuing basis with priorities determined by seed inventory and viability. 1D. Distribute on request NSGC accessions and information that meet the specific needs of researchers worldwide. Objective 2. Develop more effective genetic resource maintenance, evaluation, and characterization methods and apply them to priority small grains genetic resources; screen for host-plant resistance to virulent diseases, such as the Ug99 wheat rust strain. Record and disseminate evaluation and characterization data via GRIN-Global and other data sources. 2A. Assess putative duplicate accessions for barley and wheat. 2B. Characterize resistance to bunt and stem rust in NSGC wheat accessions. 2C. Collect remaining priority characterization data and record in GRIN-Global. Objective 3. With other NPGS genebanks and Crop Germplasm Committees, develop, update, document, and implement best management practices and Crop Vulnerability Statements for small grains genetic resource and information management. 3A. Review and update NSGC standard operating procedures for all aspects of curation and implement best management practices in coordination with other NPGS sites. 3B. Engage with small grains Crop Germplasm Committees (CGCs) to update crop vulnerability statements and identify germplasm acquisition and evaluation priorities of interest to the respective committees.
Approach
Objective 1. Acquisition priorities include the wild relatives of Triticum, Hordeum, Avena, and Oryza to fill species and ecogeographic gaps in the crop collections. Highest priority will be primary genepool relatives of these genera, identified in collaboration with the Crop Germplasm Committees (CGCs). These gaps will be addressed by collection expeditions and exchanges with other genebanks. Seed of NSGC accessions are held in medium-term storage under controlled temperature (5-6o C) and relative humidity (25%). Detailed inventory records are maintained in GRIN-Global. Seed will be provided to NLGRP for safety back up. Accessions in need of regeneration will be grown at several locations as follows: Aberdeen, Idaho in fields of the University of Idaho Research and Extension Center and in USDA-ARS greenhouses; Parlier, California at the USDA-ARS National Arid Land Plant Genetic Resource Unit; and Stuttgart, Arkansas at the USDA-ARS Dale Bumpers National Rice Research Center. Accessions will be scheduled for regeneration based on a priority matrix. Viability tests are scheduled every five years. Standard procedures for GRIN-Global Order Processing will be followed. Distributions outside of the U.S. will follow phytosanitary requirements of the recipient country, including import permits, phytosanitary certificates, and additional declarations. USDA-APHIS will be consulted regularly for the latest information on seed export. Seed shipments to other countries will be coordinated with the National Germplasm Resources Laboratory (NGRL), Plant Exchange Office. Noxious weeds will be distributed under a USDA-APHIS permit. Accessions that fall under the International Treaty for Plant Genetic Resources for Food and Agriculture will follow appropriate guidelines and will include agreement to the Standard Material Transfer Agreement by the recipient. Objective 2. Molecular markers and morphological traits will be used to develop a method to assess variation within and between NSGC wheat and barley accessions. After establishing the method, the barley and wheat collections will be sampled to measure the degree of duplication within each. Using the data from this study, verified duplicate accessions may be combined. Using genome wide association and bi-parental mapping approaches, genes for bunt and stem rust resistance will be sought within the NSGC wheat collection. Markers associated with novel resistance to the Ug99 stem rust group of races will be validated in various genetic backgrounds. Remaining priority characterization data will be collected and recorded in GRIN-Global. Objective 3. SOPs for all aspects related to acquisition, maintenance, regeneration, characterization, evaluation, and distribution will be reviewed, updated, and compiled into a complete NSGC operations manual of procedures. Through meetings and discussions with the small grains CGCs the priorities of these research communities will be identified and reflected in crop vulnerability statements and NSGC descriptors. Ongoing dialogue with the CGCs will be maintained.
Progress Report
Researchers at Aberdeen, Idaho, presently hold 147,680 accessions of small grains, which include wheat, barley, oat, rye, triticale, rice and related wild species. Seed distributions to scientists totaled 27,122 accession samples in 573 separate requests. Scientists from foreign countries continue to make up about one-third of the requests. This work supports Objective 1, to: efficiently and effectively acquire genetic resources of small grains and their wild relatives; maintain their safety, genetic integrity, health and viability; and distribute them and associated information worldwide.
New races of wheat stem rust originating in East Africa included the Ug99 lineage, which pose a threat to global bread wheat production. Ug99 races have developed virulence to many resistance genes that are currently deployed in bread wheat cultivars. ARS researchers in Aberdeen, Idaho, have systematically tested national small grains collection (NSGC) winter habit bread wheat landraces for resistance to North American and Ug99 races of stem rust. Accessions that have unique resistance patterns, and do not have molecular markers linked with known resistance genes, were crossed to known susceptible cultivars. Populations derived from these crosses were used to develop genetic maps that can identify chromosomal regions and molecular markers associated with Ug99 resistance. Screening of two spring landraces (PI 94439 and PI 117494) and three winter landrace populations (PI 58084, PI 166895 and PI 470571) with Ug99 and domestic wheat stem rust isolates was conducted at the Cereal Disease Laboratory in Njori, Kenya. Further field testing of the PI 94439 population is underway in Minnesota in collaboration with the Cereal Disease Laboratory, the International Maize and Wheat Improvement Center (CIMMYT) in Mexico City, Mexico, and the Kenya Agriculture and Livestock Organization (KALRO) in Nairobi, Kenya. PI 94439 was also resistant to wheat stripe rust in ARS trials conducted in Pullman and Mt. Vernon, Washington. Screening of the PI 94439 population is underway in both Washington locations, in collaboration with other ARS researchers, to determine if resistance to wheat stem and stripe rust in this accession is conferred by unique genetic loci. This work supports Objective 2, to: develop more effective genetic resource maintenance, evaluation, and characterization methods and apply them to priority small grains genetic resources; and screen for host-plant resistance to virulent diseases, such as the Ug99 wheat rust strain.
Oat stem rust is a persistent threat to oat forage and grain yields. In support of Objective 2, ARS researchers, in collaboration with researchers at Agriculture and Agri-Food Canada in Ottawa, Canada, are working to "fine map" the chromosomal location of Pg6, an important oat stem rust resistance gene, using a map-based, targeted sequencing technique. Two bi-parental Avena strigosa mapping populations were developed to initially map and validate markers associated with the general location of Pg6, then a targeted comparative sequence analysis in the chromosomal region of interest was utilized to design and test additional molecular markers in the target region. Markers tightly linked with resistance will be used to screen all available NSGC diploid Avena spp. accessions in order to determine which accessions likely carry this gene. This information can be used to identify new sources of oat stem rust resistance within diploid Avena germplasm. Several additional Avena sativa accessions with potentially new sources of oat stem rust resistance were tested for resistance to crown rust resistance in the Buckthorn Nursery in conjunction with researchers at the Cereal Disease Laboratory. Two accessions, PI 177867 and PI 504851, showed moderate levels of resistance to both oat stem rust and oat crown rust. These accessions were crossed with susceptible oat cultivars and can be used for mapping studies, if their observed resistance proves to be novel. Other known stem rust resistance populations developed for mapping Pg1, Pg8 and Pg10 were advanced via single seed descent for future phenotyping and mapping efforts.
Researchers collaborated with the Rice Crop Germplasm Committee to update the Rice Crop Vulnerability Statement. This work supports Objective 3 to develop, update, document, and implement best management practices and Crop Vulnerability Statements for small grains genetic resource and information management.
Accomplishments
Review Publications
Gordon, T.C., Wang, R., Bowman, B., Klassen, N., Wheeler, J., Bonman, J.M., Bockelman, H.E., Chen, J. 2020. Agronomic and genetic assessment of terminal drought tolerance in two-row spring barley. Crop Science. 60(3):1415-1427. https://doi.org/10.1002/csc2.20040.
Gordon, T.C., Wang, R., Hole, D., Bockelman, H.E., Bonman, J.M., Chen, J. 2020. Genetic characterization and genome-wide association mapping for dwarf bunt resistance in bread wheat accessions from the USDA National Small Grains Collection. Journal of Theoretical and Applied Genetics. 133:1069-1080. https://doi.org/10.1007/s00122-020-03532-0.
Boyles, R., Marshall, D.S., Bockelman, H.E. 2019. Yield data from the Uniform Southern Soft Red Winter Wheat Nursery emphasize importance of selection location and environment for cultivar development. Crop Science. 59(5):1887–1898.
Wang, R., Liu, Y., Isham, K., Zhao, W., Wheeler, J., Klassen, N., Hu, Y., Bonman, J.M., Chen, J. 2018. QTL identification and KASP markers development for productive tiller and fertile spikelet numbers in two high yielding hard white spring wheat cultivars. Molecular Breeding. 38:135. https://doi.org/10.1007/s11032-018-0894-y.
Wang, R., Gordon, T.C., Hole, D., Zhao, W., Isham, K., Bonman, J.M., Goates, B., Chen, J. 2019. Identification and assessment of two major QTL for dwarf bunt resistance in Winter Wheat Line ‘IDO835’. Journal of Theoretical and Applied Genetics. 132:2755-2766. https://doi.org/10.1007/s00122-019-03385-2.
