Location: Peanut and Small Grains Research Unit
2024 Annual Report
Objectives
Objective 1. Identify and transfer novel sources of resistance to cereal aphids and important diseases of wheat, barley, and sorghum into locally adapted lines or germplasm to improve pest and disease resistance.
Sub-objective 1A: Evaluate available germplasm resources (U.S. germplasm collections and accessible exotic resources) to identify new sources resistant to insect pests [Russian wheat aphid (RWA), greenbug (GB), bird cherry-oat aphid (BCOA), sugarcane aphid, and other important insect pests] in wheat, barley, sorghum, and related species, and transfer newly identified resistance sources into locally adapted lines.
Sub-objective 1B: Evaluate wheat germplasm to identify new sources resistant to leaf rust and powdery mildew in wheat, and introgress newly identified genes into locally adapted cultivars.
Sub-objective 1C: Develop high yielding and resistant germplasm and cultivars of wheat, barley, and sorghum.
Objective 2. Analyze the genetic basis of pest resistance and other traits important for sustainable crop production.
Sub-objective 2A: Develop and evaluate genetic populations to determine the genetic control of host resistance to GB, RWA, and BCOA in barley.
Sub-objective 2B: Develop and evaluate genetic populations to determine levels of genetic diversity of host resistance and genes controlling the resistance to RWA, BCOA, and HGA in barley.
Sub-objective 2C: Map genes conferring resistance to cereal aphids and develop genomic tools for gene cloning and marker-assisted selection of aphid resistance genes.
Sub-objective 2D: Conduct functional genomics studies on host response to attack by GB and sugarcane aphids (SCA), leading to advanced understanding of the defense mechanisms in the hosts and discovery of genes and factors that affect host defense against insect pests (i.e., GB and SCA) in sorghum and related species.
Sub-objective 2E: Discover novel leaf rust and powdery mildew resistance genes and develop genomic tools to facilitate their use in wheat cultivar development.
Approach
Wheat, barley and sorghum are major underpinnings of the agricultural economy of the U.S. Profitable, sustainable production of these commodities in the Great Plains and western U.S. is dependent on the control of aphid pests and diseases, specifically the Russian wheat aphid, greenbug, sugarcane aphid, bird-cherry oat aphid, leaf rust, and powdery mildew. Identification of natural resistance and use of genetically pest-resistant cultivars and hybrids in an integrated pest management program are the most economical and environmentally sound methods to reduce the negative economic impact of these damaging aphids and diseases. The overall goal of this project is to develop high performance wheat, barley, and sorghum with resistance to aphid pests and major diseases. To accomplish this goal, the project will search available germplasm collections to find new, effective sources of resistance to aphid pests and diseases that threaten production of those crops. The genetic diversity and resistance mechanisms will be analyzed, and resistance genes will be characterized and transferred into adapted genetic backgrounds. Plant genotyping will be conducted to map aphid and disease resistance genes to the crop chromosomes and to develop molecular markers to facilitate marker-assisted selection and map-based gene cloning. 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 traits. The genetically improved germplasm and varieties will be field-tested for agronomic and quality performance prior to release. The project will provide testing and selecting support to assure that these desirable genes move through the various breeding programs on their way to producers via sharing and releasing of genetically improved cultivars and hybrids.
Progress Report
Sub-objective 1A: Research in ARS Stillwater, Oklahoma, continued on evaluating a collection of sorghum germplasm to discover new sources of resistance to sorghum aphids. This set of germplasm included several hundreds of sorghum lines from the Germplasm Resources Infromation Network (GRIN) system and more than 30 exotic lines originated from other countries including India and African regions. This research led to the identification of 12 new sources of aphid resistance in sorghum.
Sub-objective 1A: ARS scientists in Stillwater, Oklahoma, continue to identify and transfer novel sources of resistance to cereal aphids and important diseases of wheat, barley, and sorghum into locally adapted lines or germplasm to improve pest and disease resistance. A panel of over 600 translocation lines and synthetic hexaploid wheat lines (SHW) were evaluated for responses to greenbug (Gb), leading to the identification of over 100 Gb-resistant SHW lines and translocation lines. Based on phenotypic data, two of them may carry novel Gb resistance genes, and crosses were made to identify the underlying genes and transfer the genes into locally adapted lines. More Gb biotypes will be used to further test the remaining accessions to identify those possessing new genes. The panel was also evaluated for responses to bird cherry-oat aphid (BCOA), and three lines exhibited high resistance or tolerance. Crosses will be made to identify the underlying genes and enhance BCOA resistance in FY2025. In addition, a set of about 200 durum wheat cultivars were evaluated for responses to Russian wheat aphid (RWA) biotype 1 and biotype 2, and a few resistant lines were identified.
Sub-objective 1C: Sorghum geneticist at Stillwater, Oklahoma, continued the development of breeding population. This effort includes 14 new crosses to transfer the newly identified aphid resistance to well-adapted germplasm or breeding lines to produce new varieties that carry the genetic resistance to sorghum aphids. Other research includes advancing pedigrees of previously developed breeding populations and growing the newly identified line to increase seeds for re-evaluation of the resistance and other important traits.
ARS scientists in Stillwater, Oklahoma, continue to identify and transfer novel sources of resistance to cereal aphids and important diseases of wheat, barley, and sorghum into locally adapted lines or germplasm to improve pest and disease resistance. 1100 spring barley accessions from the National Small Grain Collection (NSGC) and 200 progenies from previously rescued resistant accessions were screened to BCOA. A total of 720 F2 from 7 crosses were also screened. Crosses between survivors from 2022/2023 barley BCOA screening as males and Morex and 4, spring, RWA-resistant germplasm lines (STARS 0620B, STARS 0621B, STARS 0627B, and STARS 0635B) as females were made. A backcross breeding program continues in 2024 to transfer BCOA resistance into adapted malting and feed barley backgrounds. Four new greenbug resistant genes have been identified in the past 2 years with a 5th gene identified this year. Homozygous resistant F7 lines with one of these new resistant genes are currently being evaluated in the field in replicated trials at 2 locations in Oklahoma prior to release as a germplasm line. Homozygous resistant F7 lines from the other 4 populations are currently being increased in the greenhouse and will be field tested in 2025. Selected lines will be released as germplasm lines. F2 head selections from 146 malting barley populations in 2023 were screened for resistance to RWA and greenbug in the greenhouse and 5,500 resistant lines are currently being increased in the greenhouse for future field evaluation. 2,500 winter malting barley lines are currently being evaluated as single F4 rows in Woodward, Oklahoma. Selected lines will be planted in replicated yield trials in 2025. Head selections are currently being made from 23 F2 populations. Seventy-three malting barley lines are currently being evaluated in replicated yield trials at 2 locations in Oklahoma. The Uniform Winter Barley Nursery is being evaluated in Woodward, Oklahoma. A multi-state field survey was conducted this spring to determine the establishment of hedgehog grain aphid (HGA) in the inner-mountain regions of the Rockies and plains to the west and east. A follow-up survey is planned for this fall.
Sub-objective 2C: Sorghum research team developed additional simple sequence repeat (SSR) markers and single nucleotide polymorphism (SNP) markers for fine mapping the aphid resistance genes. These DNA markers will allow us to precisely locate the aphid resistance gene(s) on the sorghum chromosomes.
Research continued discovering novel greenbug and RWA resistance genes. A novel gene conferring resistance to all U.S. RWA biotypes, designated Dn625139, was identified and located in the proximal region of the short arm of chromosome 7D. Kompetitive Allele specific PCR (KASP) markers closely linked to this gene were developed for its application in wheat breeding. In addition, genetic analysis was conducted to characterize the greenbug resistance genes in the synthetic hexaploid wheat line CWI 76364, leading to the identification of a new greenbug resistance gene, officially designated Gb9, in the terminal region of the long arm of chromosome 7D. KASP markers were also developed to facilitate the use of Gb9 in wheat breeding.
Sub-objective 2D: Sorghum researcher continued his effort on functional genomics studies of sorghum plants’ responses to aphid infestation using the gene expression profiles of infested and non-infested sorghum plants. Thus, a group of aphid-responsive genes were identified and subsequently those genes are characterized at the molecular level. Those results provide new insights into elucidation of the host plant defense mechanisms in sorghum.
Accomplishments
Review Publications
Henyou, Z., Huang, Y. 2024. Genome-wide identification and characterization of greenbug-inducible NAC transcription factors in sorghum. Molecular Biology Reports. https://doi.org/10.1007/s11033-023-09158-x.
Huang, Y., Huang, J. 2023. Analysis of plant expression profiles revealed that aphid attack triggered dynamic defense responses in sorghum plant. Frontiers in Genetics. 14. Article 1194273. https://doi.org/10.3389/fgene.2023.1194273.
Xu, X., Mornhinweg, D.W., Bai, G., Li, G., Bian, R., Bernardo, A.E., Armstrong, J.S. 2023. Identification of a new Rsg1 allele conferring resistance to multiple greenbug biotypes from barley accessions PI 499276 and PI 566459. The Plant Genome. https://doi.org/10.1002/tpg2.20418.
Hayashida, R., Armstrong, J.S., Hoback, W., Mornhinweg, D.W. 2023. Physiological and morphological responses of susceptible and resistant barleys to bird cherry-oat aphid feeding. American Journal of Plant Sciences. 14(10):1115-1129. https://doi.org/10.4236/ajps.2023.1410076.
Xu, X., Li, G., Bai, G., Bian, R., Bernardo, A.E., Kolmer, J.A., Carver, B.F., Wolabu, T.W., Wu, Y. 2024. Characterization of quantitative trait loci for leaf rust resistance in the Uzbekistani wheat landrace Teremai Bugdai. Phytopathology. 114:1373-1379. https://doi.org/10.1094/PHYTO-09-23-0320-R.
Xu, X., Li, G., Bai, G., Bian, R., Bernardo, A.E., Watira, T.W., Carver, B.F., Wu, Y., Elliott, N.C. 2024. Characterization of a new greenbug resistance gene Gb9 in a synthetic hexaploid wheat. Theoretical and Applied Genetics. 137. Article 140. https://doi.org/10.1007/s00122-024-04650-9.
Shrestha, K., Huang, J., Yan, L., Doust, A., Huang, Y. 2024. Integrated transcriptomic and pathway analyses of sorghum plants revealed the molecular mechanisms of host defense against aphids. Frontiers in Plant Science. 15. Article 1324085. https://doi.org/10.3389/fpls.2024.1324085.
Zhao, L., Lu, Y., Zhang, X., Zhao, W., Xu, X., Wang, H., Zhang, G., Fritz, A., Fellers, J.P., Guttieri, M.J., Jordan, K., Bai, G. 2024. Characterization of quantitative trait loci for leaf rust resistance from CI 13227 in three winter wheat populations. Journal of Phytopathology. 114(8):1869-1877. https://doi.org/10.1094/PHYTO-03-24-0108-R.