Location: Wheat, Sorghum and Forage Research
2024 Annual Report
Objectives
Objective 1. Develop winter wheat and barley germplasm with Great Plains priority traits, including resistance to fungal and viral pathogens, wheat bacterial leaf streak, and insects, and durum germplasm with improved nutritional quality.
Subobjective 1A: Characterize and map disease resistance genes for Fusarium head blight (FHB), stem rust (Sr), and wheat stem sawfly (WSS) in wheat.
Subobjective 1B: Develop diagnostic and user-friendly molecular markers to assist FHB resistance introgression.
Subobjective 1C: Integrate genes for resistance to FHB, stem rust, bacterial leaf streak (BLS), wheat stem sawfly, and nutritional end-use quality into high-yielding Great Plains winter wheat for germplasm development.
Objective 2. Discover new genes for resistance to major diseases and insects in wheat and barley, and introgress them into adapted germplasm.
Subobjective 2A: Identify and characterize novel genes for disease resistance from the relatives of wheat and barley.
Subobjective 2B: Introduce the relative-derived novel genes for resistance to diseases into wheat and barley.
Subobjective 2C: Develop unique genetic stocks and genomic resources useful in the wheat genome study and wheat breeding.
Objective 3. Identify, characterize, and utilize host susceptibility genes for the management of wheat streak mosaic disease complex.
Subobjective 3A: Examine the wheat response to synergistic interaction between wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) in wheat.
Subobjective 3B: Identify viral and host proteins involved in synergistic interaction between WSMV and TriMV in wheat.
Subobjective 3C: Target the host factors involved in synergistic interaction between WSMV and TriMV by VIGS, RNAi, and CRISPR/Cas9.
Subobjective 3D: Identify WSMV determinants involved in Wsm-resistance breaking.
Subobjective 3E: Pyramid WSMV NIa-Pro transgene with natural resistance genes, Wsm1 and/or Wsm2.
Objective 4. Coordinate the USDA-ARS Hard Winter Wheat Regional Nursery Program and the USDA-ARS African Winter Wheat Stem Rust Nursery.
Subobjective 4A: Utilize the HWWRNP to determine the yield potential and stability of newly developed Great Plains Winter Wheat Germplasm with priority traits and distribute the germplasm to Great Plains wheat breeding programs.
Subobjective 4B: Coordinate the USDA-ARS African Winter Wheat Stem Rust Nursery in Njoro, Kenya.
Approach
Wheat (Triticum spp.) and barley (Hordeum vulgare L.) are important crops for human and animal consumption and the beverage industry. Wheat and barley production is continually threatened by bacterial, fungal, and viral diseases that have the potential to form epidemics of substantial economic impact with up to 25-30% annual yield losses. The main objective of this project is to develop elite hard winter wheat, soft and hard winter durum wheat, and barley germplasm with broad genetic diversity, improved disease resistance, and enhanced end-use quality and nutrition. We will utilize genomics-enabled breeding to incorporate priority traits into wheat and barley for germplasm development from native sources and their relatives. The new sources of resistance will be identified, characterized, and deployed in wheat against Fusarium head blight (FHB), stem rust, wheat streak mosaic, wheat bacterial leaf streak diseases and wheat stem sawfly, and in barley against FHB disease. Wheat susceptibility genes for wheat streak mosaic virus (WSMV) will be identified and utilized for resistance against WSMV, which could prevent synergistic interaction with the Triticum mosaic virus. Ultimately, the adapted wheat and barley germplasm will be developed with natural pathogen resistance and enhanced protein and end-user functionality. The project comprises three integrated components of germplasm development and characterization, viral genetics and plant pathology, and wheat end-use quality. This project will be implemented on a scale of DNA molecules to chromosomes to field level to achieve the research goals using cytogenetics, genomics, molecular virology, and conventional breeding methodologies. Additionally, we will coordinate and manage the Hard Winter Wheat Regional Nursery program and the African Stem Rust Nurseries and evaluate the wheat germplasm and cultivars developed by the Great Plains public and private breeding programs for disease resistance and agronomic performance in multiple environments.
Progress Report
Various biotic and abiotic stresses, such as disease pathogens, pests, and climate change, threaten wheat and barley production. Hence, we are working to improve the genetic potential of wheat and barley to address these challenges and ensure sustainable small-grain production in the face of these evolving threats. Research was conducted to identify, characterize, and utilize disease-resistant and quality-related genes in wheat and barley for new germplasm/variety development.
Objective 1: The novel tall wheatgrass-derived fusarium head blight (FHB) resistance gene Fhb7The2 was deployed into three elite hard red spring wheat lines through breeding efforts to bolster FHB resistance while maintaining favorable agronomic traits. These three lines have been evaluated for FHB resistance and agronomic performance. In addition, the FHB resistance gene Fhb7The2 was incorporated into other breeding lines representing the market classes of hard red winter wheat (HRWW), spring and winter durum wheat, and barley. Advanced HRWW and durum breeding lines containing the Fhb7The2 gene have been developed and evaluated for FHB resistance. Additionally, molecular markers have been developed to assist breeding efforts for FHB resistance in wheat and barley. Deployment of this novel wild grass-derived FHB resistance gene in wheat and barley will strengthen and diversify the resistance of wheat and barley to FHB and reduce the economic losses this disease causes to wheat and barley growers.
Six recombinant inbred line (RIL) populations were developed for the introgression of bread wheat-derived FHB resistance genes into durum wheat. Three populations were genotyped using molecular markers and rated for FHB resistance. The gene mapping efforts and understanding of gene interactions will provide a better understanding of the bread wheat-derived FHB resistance genes in durum wheat and enable their use in durum breeding efforts.
Winter durum wheat accessions were identified with the solid stem trait for wheat stem sawfly (WSS) resistance and were subsequently evaluated for stem solidness and other agronomic traits. We anticipate developing winter durum germplasm/varieties with solid stems (WSS resistant), desirable on-farm performance and desired quality traits.
Over forty stem rust (Sr) accessions from all over the world were previously screened for Sr-resistance and thought to harbor unknown or uncharacterized Sr-resistance genes. These accessions were screened for winter survival/hardiness. Nearly 50% of the Sr accessions were rated at a 100% survival rate, indicating their potential utility in winter wheat breeding efforts. Additionally, we developed new RIL mapping populations by crossing many of the resistant Sr accessions to Great Plains-adapted susceptible varieties.
A total of 178 winter durum breeding lines were screened for winter survival/hardiness, heading date, yield, protein, moisture, and test weight. The highest-yielding lines will be chosen to advance into replicated and randomized yield trials. Furthermore, new crosses were performed between soft spring durum lines with segments of bread wheat chromosomes that were selected for milling traits (to produce flour, not semolina) and bread-making traits. Our aim is to produce new soft winter durum lines with novel end-use quality traits for commercial uses.
Objective 2: More than 200 rye accessions were screened for bacterial leaf streak (BLS) resistance, and we identified dozens of accessions with various levels of resistance to BLS. In addition, the triticale accessions with BLS resistance were crossed to common and durum wheat and ph1b mutant for introgression of the resistance gene from rye into wheat. Chromosome compositions of the progenies from the crosses were analyzed to induce wheat-rye chromosome recombination. Molecular markers were developed for BLS resistance gene introgression from rye chromosome 5R to wheat chromosome 5D. Furthermore, we developed additional molecular markers specific for homoeologous recombination-based alien introgression in different common and durum wheat genotypes.
Over 200 wheat-alien species derivative lines were evaluated in a replicated experiment for wheat streak mosaic virus (WSMV) resistance. Eleven of the derivative lines were identified as resistant to WSMV, and nine of them elicited a hypersensitive reaction to WSMV with no detectable levels of virus accumulation. The derivative WSMV-resistant lines were crossed to common and durum wheat and ph1b mutant for resistance introgression from alien chromosomes into the wheat genome.
Objective 3: WSMV and Triticum mosaic virus (TriMV) are economically important wheat viruses, causing the wheat streak mosaic disease complex with $70-90 million annual losses in the USA. In co-infected wheat, WSMV and TriMV interact synergistically with exacerbated disease phenotype. Since these two viruses are transmitted by a common vector, wheat curl mites, mixed infection in growers’ fields is common, with nearly 100% yield loss. To examine the effect of co-infection of WSMV and TriMV on the wheat transcriptome, total RNA from wheat plants infected by WSMV, TriMV, or WSMV+TriMV was used for wheat transcriptome analysis by using high-throughput RNA sequencing.
Recently, WSMV isolates infected wheat cultivars harboring the Wsm2 gene. Two Wsm2-resistance breaking isolates were collected from Kansas, and these field-collected isolates were purified from TriMV infection by infecting a corn inbred line SDp2, which is a non-host for TriMV. The genome sequence of Wsm2-resistance-breaking WSMV isolates was completely determined. WSMV isolates Hays294 and Hamilton possessed 98.2% and 99.3% sequence identity, respectively, with WSMV isolate Sidney 81, a predominant isolate in the Great Plains area.
Wheat lines with a WSMV gene as a transgene provided resistance at 27°C and 20°C. To improve the temperature-sensitive resistance of wheat cultivars/lines containing Wsm1, Wsm2, or Wsm3 genes, we utilized the gene pyramiding strategy to stack the transgene with natural resistant genes. Two transgenic lines were crossed with cultivars or lines carrying the Wsm1, Wsm2, or Wsm3 genes, and wheat seed from the F1 generation was collected for further screening to obtain homogeneous populations.
Barley yellow dwarf (BYD) and cereal yellow dwarf (CYD) viruses produce yellow dwarf disease in cereal crops and include a complex of five major strains in the USA. A state-wide wheat field survey was conducted to understand BYDV/CYDV strain composition in Nebraska. We found that approximately 60% of samples tested positive for at least one strain of BYDV/CYDV. BYDV strain SGV was the most abundant strain and was the only strain present as both single- (approximately 20%) and co-infection (approximately 50%) with other B/CYDV strains.
Objective 4: The 2024 Hard Winter Wheat Regional Performance Nurseries consisting of the Northern and Southern Regional Performance Nurseries (NRPN, SRPN) and the Regional Germplasm Observation Nurseries (RGON) and the 2024 USDA-ARS African winter wheat and barley stem rust nursery (ASrN) were each successfully coordinated. Breeder seed (nursery entries) for each of the NRPN, SRPN, RGON, and ASrN was successfully received and distributed to all collaborators for yield trials, disease screening efforts, genotyping, and end-use quality analyses. All four nurseries provide valuable data to wheat and barley breeders from private companies and public universities nationwide to develop and release new wheat and barley cultivars.
Accomplishments
1. Deployment of the new fusarium head blight (FHB) resistance gene Fhb7The2 in hard red spring wheat. Deployment of the new fusarium head blight resistance gene Fhb7The2 in hard red spring wheat. There is an urgent need to find and deploy new fusarium head blight (FHB) resistance genes in wheat to fight against this devastating disease, which has caused billions of dollars in losses to United States growers since 1993. ARS scientists in Lincoln, Nebraska, deployed the new wild grass-derived FHB resistance gene Fhb7The2 by developing new hard red spring wheat (HRSW) lines containing the resistance gene using modern and conventional breeding technologies. Three elite FHB-resistant HRSW breeding lines were developed and subsequently evaluated for FHB resistance in the greenhouse and two field locations across multiple seasons. These lines have consistently exhibited significant resistance to FHB across locations and seasons, demonstrating the utility of this wild grass-derived FHB resistance gene to protect wheat from this disease. These three FHB-resistant HRSW breeding lines will be very useful for breeding FHB resistance into other market classes of U.S. wheats. This discovery adds a new tool for wheat growers to combat FHB and reduce on-farm economic losses attributed to the disease.
2. Triticum mosaic virus HC-Pro is a determinant of wheat curl mite transmission. Triticum mosaic virus helper component proteinase is a determinant of wheat curl mite transmission. Triticum mosaic virus (TriMV) causes economically significant damage to wheat in the Great Plains region. Wheat curl mites transmit this virus from infected to healthy wheat plants in growers’ fields. Blocking wheat curl mites from transmitting the virus can prevent the spread of the virus in wheat fields. Disrupting the molecular interactions between viral and mite proteins will block virus transmission and prevent its spread. The first step is to identify the virus proteins required for mite transmission. ARS scientists in Lincoln, Nebraska, determined that the helper component proteinase protein of the virus was required for wheat curl mite transmission of TriMV. These results will lead to new management strategies through RNA-interference technology to disrupt virus-mite interactions and prevent wheat curl mites from transmitting TriMV to wheat.
Review Publications
Tatineni, S., Alexander, J.A., Kovacs, F. 2023. HC-Pro cistron of Triticum mosaic virus is dispensable for systemic infection in wheat but is required for symptom phenotype and efficient genome amplification. Virus Research. 339. Article 199277. https://doi.org/10.1016/j.virusres.2023.199277.
Soylu, I., Tatineni, S., Lakshman, D.K., Galvez, L., Mitra, A. 2024. Differential regulation of miRNAs involved in the susceptible and resistance responses of wheat cultivars to wheat streak mosaic virus and Triticum mosaic virus. BMC Genomics. 25. Article 221. https://doi.org/10.1186/s12864-024-10128-1.
Wang, N., Sundin, G.W., De La Fuente, L., Cubero, J., Tatineni, S., Brewer, M.T., Zeng, Q., Bock, C.H., Cunniffe, N.J., Wang, C., Candresse, T., Chappell, T., Coleman, J.J., Munkvold, G. 2024. Key challenges in plant pathology in the next decade. Phytopathology. 114(5):837-842.
Morgan, R., Danilova, T.V., Newell, M., Cai, X., Jones, S. 2023. Agronomic evaluation and molecular cytogenetic characterization of Triticum aestivum x Thinopyrum spp. derivative breeding lines presenting perennial growth habit. Plants. 12(18). Article 3217. https://doi.org/10.3390/plants12183217.
Talukder, M.I., Underwood, W., Misar, C.G., Li, Z., Seiler, G.J., Cai, X., Qi, L. 2023. Genetic analysis of basal stalk rot resistance introgressed from wild Helianthus petiolaris into cultivated sunflower (Helianthus annuus L.) using an advanced backcross population. Frontiers in Plant Science. 14. https://doi.org/10.3389/fpls.2023.1278048.