Location: Wheat Health, Genetics, and Quality Research
2023 Annual Report
Objectives
This project will work to achieve the following objectives over the next five years:
1) Monitor and characterize stripe rust pathogen populations towards the development of appropriate measures to reduce damage on wheat and barley.
2) Enhance resistance in wheat and barley cultivars for effective stripe rust control.
Approach
For Objective 1 (Monitor and characterize stripe rust pathogen populations towards the development of appropriate measures to reduce damage on wheat and barley), we will use our models for the Pacific Northwest (PNW) to predict stripe rust epidemic levels. To monitor and mange stripe rust, we will conduct field survey and provide rust updates and recommendations to growers to implement appropriate control measures. To identify stripe rust races, rust samples will be collected from cereals (wheat, barley, rye, and triticale) and various grasses by collaborators and ourselves during surveys, and the isolates will be characterized for virulence using our standard protocols of our program. To identify population changes, we will use a standard set of 14 SSR markers to characterize stripe rust isolates. We will also identify SNP markers associated to avirulence genes and converted them into KASP markers. KASP markers with the highest value of correlation coefficient will be selected to establish a set of KASP markers for avirulence genes.
For Objective 2 (Enhance resistance in wheat and barley cultivars for effective stripe rust control), we will screen wheat, barley, and triticale lines from breeding programs throughout the U.S for developing new resistant varieties. To determine the stripe rust resistance levels, potential yield losses, and response to fungicide application of commercially grown varieties, each year we will evaluate 23 winter and 23 spring wheat varieties from the Pacific Northwest, plus a susceptible check in each nursery. The results of these tests will be used to guide growers for selecting resistance varieties and appropriately use of fungicides. For identifying new geremplasm and stripe rust resistance genes, we will complete the studies of mapping and identifying stripe rust resistance in three wheat panels using the genome-wide association study (GWAS) approach. We will also focus on mapping and identifying genes for resistance to stripe rust in the 40 crosses made from 40 winter wheat varieties crossed with susceptible AvS. We have identified 233 SNP markers associated to stripe rust resistance using a bulk-segregant approach for at least 70 individual genes in the 40 varieties. The SNP markers will be validated using the individual bi-parental mapping populations. The SNP markers for new resistance loci will be converted to KASP markers. New germplasm lines carrying new genes will be selected based on morphological plant types, stripe rust reactions, and molecular markers, and these lines will be deposited and registered in the ARS National Small Grain Collections.
Progress Report
This report documents fiscal year (FY) 2023 progress for project 2090-22000-020-000D, Enhancing Control of Stripe Rusts of Cereal Crops. Progress was made on the both objectives, all of which fall under National Program 303 Plant Diseases.
In support of Objective 1, ARS scientists in Pullman, Washington, completed all tests for identifying races from the stripe rust collections in the United States in 2022, and reported the results to the cereal community of researchers, developers, and growers. During the 2023 crop season, they accurately predicted the potential stripe rust level of the season in the winter and early spring, conducted field surveys, made recommendations for stripe rust management, which successfully prevented unnecessary use of fungicides and saved growers’ multimillion dollars in the Pacific Northwest (PNW). By collecting stripe rust samples in the PNW and through collaborators in other regions, they obtained more than 250 stripe rust samples from 13 states. Spores from these samples were recovered and multiplied on susceptible wheat plants in the greenhouse to establish isolates. Each isolate was tested on the set of wheat or barley differentials for identifying races of the wheat or barley stripe rust pathogen. From the 2022 samples, they identified 22 races of the wheat stripe rust pathogen and 12 races of the barley stripe rust pathogen and determined the distributions and frequencies of the races and virulence factors. From the 2023 collection, nine races, including three potential new races, of the wheat stripe rust pathogen and three races of the barley stripe rust pathogen have been identified so far. Based on the virulence data of the races, resistance genes, such as Yr5, Yr15, and many other genes identified by this program and other programs in the world, have been determined to be effective against all populations of the wheat stripe rust pathogen in the United States, and these genes can be used in breeding programs for developing stripe rust resistant wheat cultivars. Similar information has also been obtained for the barley stripe rust pathogen and barley resistance genes. Based on the virulence patterns, distributions, and frequencies of various races, they selected races for use in their wheat and barley germplasm screening research. The progress of race identification is on schedule.
For molecular characterization of the stripe rust pathogen populations, ARS scientists in Pullman, Washington, has continued characterized the wheat stripe rust collections from 2018 to 2023 in the United States after they published the results from the 1960s to 2017 using a set of simple sequence repeat (SSR) markers.
In support of Objective 2, ARS scientists in Pullman, Washington, planted more than 16,000 wheat and barley entries in the fields near Pullman, Mount Vernon, and Central Ferry, Washington, for screening the materials for resistance to stripe rust. Some of the nurseries were also planted in three additional locations in Walla Walla and Lind, Washington. They have completed collecting stripe rust response data for the nurseries planted in the different locations. They also have tested the wheat and barley variety trial nurseries and uniform nurseries from various wheat and barley production regions of the United States in both seedling and adult-plant stages with selected races of the stripe rust pathogen in the greenhouse. The tests in both field and greenhouse allow identifying different types and levels of resistance to stripe rust as well as which entries are resistant and which ones are susceptible. They have provided the data to various breeding programs throughout the country for selecting resistant lines for releasing as new varieties. The test results of currently grown varieties are used to update stripe rust ratings for the wheat and barley varieties listed in Seed-Buying Guides to be selected by growers to grow. Growing resistant varieties will reduce the potential risk of stripe rust damage.
To provide precise recommendations for managing stripe rust based on the resistance levels of individual varieties, ARS scientists in Pullman, Washington, tested 19 fungicide treatments for control of stripe rust and 24 winter and 24 spring commercially grown wheat varieties for response to fungicide application during the 2023 crop season. The efficacies of fungicides and responses of fungicide application verses non application of the commercially grown varieties should be useful for managing stripe rust based on individual varieties under different epidemic levels.
ARS scientists in Pullman, Washington, have continued identifying and mapping new genes in wheat for resistance to stripe rust. They have completed phenotyping and genotyping three wheat germplasm panels including two winter wheat panels and one spring wheat panel (each panel consisting of 420 to 520 entries) for genome-wide association studies (GWAS) for identifying genes for resistance to stripe rust. They are continually analyzing the data to complete the studies. Continuing their studies for identifying and mapping stripe rust resistance in 40 winter wheat bi-parental mapping populations, they repeated the field experiments in both Pullman and Mount Vernon, Washington, for obtaining more sets of stripe rust phenotypic data of the selected mapping populations. They have completed a study of identifying a new gene officially named Yr85 for resistance to stripe rust and published the results in Plant Disease in 2023. They also mapped five stable quantitative trait loci for all-stage and high-temperature adult-plant resistance in wheat germplasm line PI 660122 that was previously developed in their program, and they have just published the results in Frontiers in Plant Science. The identified resistance genes and the developed molecular markers make PI 660122 more useful in breeding programs for developing new wheat varieties with stripe rust resistance.
Accomplishments
1. Screened wheat and barley germplasms and released new wheat varieties for resistance to stripe rust. Developing resistant varieties is the most effective, easy-to use, and environmental-friendly approach to control stripe rust. ARS scientists in Pullman, Washington, screened more than 16,000 wheat and barley germplasm from breeding programs throughout the United States in multiple field locations and in the greenhouse with multiple races of the pathogen for response to stripe rust in 2023. They have provided the data to various breeding programs for releasing new resistant varieties and to growers for selecting released resistant varieties to grow. Based on their stripe rust data in recent years, they collaborated with various breeding programs in releasing and registering 13 new wheat varieties with resistance to stripe rust. Growing these new varieties will reduce potential risk of stripe rust.
2. Identified races of the wheat and barley stripe rust pathogens. The wheat and barley stripe rust pathogens evolve rapidly to produce new races that can overcome resistance in currently grown varieties, and the information of races with their virulence factors is essential for breeding programs to use effective genes for developing new varieties with adequate and durable resistance. ARS scientists in Pullman, Washington, identified 22 races of the wheat stripe rust pathogen and 12 races of the barley stripe rust pathogen from the U.S. 2022 collections, and determined the frequencies and distributions of these races and virulence factors in various epidemic regions. The results can be used by breeders to select effective resistance genes for developing new varieties and by pathologists to select important races for screening wheat and barley germplasm for releasing new varieties with adequate and durable resistance to stripe rust.
3. Identified and mapped new genes for resistance to stripe rust in wheat germplasms. Stripe rust is best controlled through developing and growing resistant varieties. ARS scientists in Pullman, Washington, completed studies on identification and molecular mapping of genes or quantitative trait loci (QTL) for stripe rust resistance in wheat germplasms. Through stripe rust phenotyping and molecular genotyping of bi-parental mapping populations, they identified a new gene, officially named Yr85, for resistance to stripe rust in a wheat line used to differentiate races of the wheat stripe rust pathogen and in a collaborative study mapped five stable QTL for all-stage resistance and high-temperature adult-plant resistance in wheat germplasm PI 660122 previously developed in their program. The identified genes/QTL and developed molecular markers are useful for plant pathologists to monitor races of the wheat stripe rust pathogen and wheat breeders to develop new wheat varieties with stripe rust resistance.
4. Identified new fungicides for control of stripe rust and determined yield losses and fungicide responses of wheat varieties. Stripe rust can be controlled by planting resistant varieties and applying fungicides when needed. To develop an integrated strategy for efficiently managing stripe rust, ARS scientists in Pullman, Washington, tested 19 fungicide treatments on susceptible varieties of both winter and spring wheats for their efficacies on control of stripe rust and determined yield losses caused by stripe rust and fungicide responses in reduction of yield losses of 24 winter and 24 spring wheat varieties used in production. The fungicide trials identified new effective fungicides, and the tests of commercially grown varieties determined yield losses caused by stripe rust and yield increases by the currently standard fungicide application for individual varieties. The results can be used by chemical companies to register new fungicides and growers to determine if fungicide application should be needed based on varieties planted in their fields and which fungicide should be selected.
Review Publications
Chen, X., Evans, C.K., Sprott, J.A. 2023. Evaluation of foliar fungicides for control of stripe rust on winter wheat in 2022. Plant Disease Management Reports. 17. Article CF035.
Chen, X., Evans, C.K., Sprott, J.A. 2023. Evaluation of foliar fungicides for control of stripe rust on spring wheat in 2022. Plant Disease Management Reports. 17. Article CF034.
Chen, X., Sprott, J.A., Evans, C.K., Qin, R. 2023. Evaluation of Pacific Northwest winter wheat cultivars to fungicide application for control of stripe rust in 2022. Plant Disease Management Reports. 17. Article CF033.
Chen, X., Sprott, J.A., Evans, C.K. 2023. Evaluation of Pacific Northwest spring wheat cultivars to fungicide application for control of stripe rust in 2022. Plant Disease Management Reports. 17. Article CF032.
Ji, F., Zhang, J., Chen, X., Liu, B., Zhou, A., Feng, Y., Zhoa, J., Huang, L., Kang, Z., Zhan, G. 2023. Effects of flubeneteram on inhibiting the development of Puccinia striiformis f. sp. tritici in wheat leaves. Journal of Agricultural and Food Chemistry. 71(13):5162-5171. https://doi.org/10.1021/acs.jafc.3c00499.
