Location:2008 Annual Report
1a. Objectives (from AD-416)
The long term goal of this project is to reduce losses in wheat and barley yield and quality caused by stripe, leaf, and stem rusts, and assure stable,sustainable wheat and barley production while protecting the environment. Over the next five years we will focus on the following objectives: 1)determine factors influencing epidemic development and host-pathogen interactions for rusts, including to identify and monitor emerging races of stripe rust on a national basis and to improve rust prediction and integrated control; 2)evaluate germplasm and breeding lines of wheat and barley for resistance to rusts,including to support breeding programs in developing cultivars with adequate and durable resistance and to identify new sources and genes of effective resistance to stripe rust; and 3)determine the genomic structure and functional genes of the stripe rust pathogen and molecular mechanisms of plant-pathogen interactions.
1b. Approach (from AD-416)
The prevalence, severity, and distribution of rusts will be monitored through disease surveys in commercial fields, monitoring nurseries, and experimental plots of wheat and barley, as well as wild grasses. Stripe rust races will be identified by testing rust samples on wheat and barley differential genotypes. Rust epidemics will be predicted based on environmental and cropping system factors. Geographic regions where stripe rust can over-winter and over-summer will be mapped by analyzing climatic and cropping data. Disease forecasting models will be developed for various epidemic regions by analyzing historical weather and disease data and tested with rust survey data. Fungicide tests will be conducted to identify new effective fungicides. Germplasms and breeding lines of wheat and barley will be evaluated in greenhouses with selected races and in field plots under natural infections of rusts to support breeding programs. New sources and genes of effective resistance to stripe rust will be identified through germplasm evaluation, genetic studies, and molecular mapping. Molecular markers for resistance genes will be developed using resistance gene analog, microsatellite, and other marker techniques. The genomic structure and functional genes of the stripe rust pathogen and molecular mechanisms of plant-pathogen interactions will be determined through constructing physical and functional gene maps. Fingerprinting and end-sequencing bacterial artificial chromosome (BAC) clones will be conducted to construct the physical map, which will be filled with functional genes identified from cDNA clones of the pathogen. Functional genes will be identified by comparing the sequences of full-length cDNA clones to genes in GenBank databases. Molecular markers will be developed using sequences of functional genes and BAC-ends for studying population structures of the stripe rust pathogen. Genes of wheat and the stripe rust pathogen involved in the plant-pathogen interactions will be identified. Formerly 5348-22000-010-00D (3/07).
3. Progress Report
In 2008, we conducted monitoring and forecasting for stripe rust and provided disease updates to growers in the Pacific Northwest (PNW). Through cooperators in other states, stripe rusts of wheat and barley were monitored throughout the US. As a result of our disease monitoring, accurate forecasting, timely alerts, and advices for disease management, wheat growers in the hard red winter wheat growing regions in Washington timely applied fungicides in the middle of April, which not only stopped stripe rust in these regions, but also reduced rust inoculum for other major wheat growing regions in the PNW. The rust management program prevented major yield losses and saved growers’ multimillion dollars by preventing unnecessary use of fungicides in many other regions through our timely rust updates and suggestions. We completed testing of 240 stripe rust samples obtained from 15 states in 2007 and we have finished 60% of more than 300 samples in 2008 so far for identification of races. From the 2007 samples, we identified 5 barley stripe rust races and 30 wheat stripe rust races, of which 11 were new. The information on predominant races and especially on new races is essential for breeding programs to select effective genes to develop resistant cultivars. To support breeding programs throughout the US, we evaluated more than 20,000 wheat and barley entries for resistance to stripe rust. The data of stripe rust evaluation were provided to breeding programs for developing new cultivars with adequate resistance, and to growers for selecting resistant cultivars to grow. Through our testing for resistant breeding lines, the WSU breeding programs released five and breeding programs in other states released several new wheat cultivars with stripe rust resistance in 2008. To identify new genes and develop molecular markers for resistance genes, we completed studies of mapping two all-stage resistance genes and three genes for high-temperature adult-plant (HTAP) resistance to stripe rust in wheat cultivars. To understand molecular mechanisms of durable resistance to stripe rust, we completed the study to profile the expression of genes regulated by the Yr39 gene for non-race-specific, durable HTAP resistance using wheat gene-chips. We identified genes involved in HTAP resistance and determined molecular mechanisms different from our previously identified mechanisms for all-stage resistance. In the microarray study, we also identified expression level polymorphism (ELP) and single feature polymorphism (SFP) markers, which have potential in marker-assisted selection for developing resistant cultivars and cloning resistance genes. We evaluated nine foliar fungicide treatments for control of stripe rust and identified better formulations. We also determined yield losses of 32 wheat cultivars grown in the PNW and their responses to fungicide application. The results of fungicide tests are essential for registration of new fungicides and for growers to obtain maximum profit from use of fungicides. This research is relevant to NP303, Component 2, Problem Statement 2C.
1. Evaluated wheat and barley germplasms and breeding lines for resistance to stripe rust. For control of the rust diseases, it is critical to identify more resistant germplasms and to select resistant breeding lines of wheat and barley for resistance. In 2008, the ARS scientists at the Wheat Genetics, Quality Physiology, and Disease Research Unit in Pullman, WA, evaluated more than 15,000 wheat and 5,000 barley entries for stripe rust resistance. From the evaluation studies, we identified new germplasm and advanced breeding lines with stripe rust resistance and established core collections of wheat and barley germplasms with resistance to stripe rust. These core germplasm collections can be used for identifying new genes for resistance to stripe rust. The data and information of stripe rust evaluation were provided to breeding programs for eliminating potential susceptible cultivars, and developing new cultivars with adequate resistance. Through our rust resistance evaluation and providing resistance resources and molecular markers for resistance genes, the WSU breeding programs released five new wheat cultivars with stripe rust resistance and private companies in Washington and breeding programs in other states released numerous wheat and barley cultivars in 2008. This research addresses NP303 (Plant Diseases) Component 3 (Plant Disease Resistance), Problem Statement 3B: Disease Resistance in New Germplasm and Varieties.
2. Determined molecular mechanisms for Yr39-mediated durable high-temperature adult-plant resistance to the stripe rust pathogen. Understanding plant–pathogen interactions is essential for effectively use of genetic resistance to control diseases like stripe rust. Yr39 confers high-temperature adult-plant (HTAP) resistance that is non-race-specific and durable against the wheat stripe rust pathogen. In a microarray study, the ARS scientists at the Wheat Genetics, Quality Physiology, and Disease Research Unit in Pullman, WA used the Wheat GeneChip® to profile the gene expression changes occurring in two wheat lines that differed for the presence of the Yr39 gene after inoculation with the stripe rust pathogen. We identified numerous resistance and defense-related genes involved in the durable type resistance. Molecular mechanisms found for HTAP resistance were different from those identified previously for race-specific all-stage resistance. The results provide novel insights into the molecular basis of durable type resistance, and the findings will be useful for the development of durable resistant cultivars. This research addresses NP303 (Plant Diseases) Component 3 (Plant Disease Resistance), Problem Statement 3A: Mechanisms of Plant Disease Resistance.
3. Accurately predicted and monitored stripe rust in 2008. Accurate disease forecast is essential for timely management of the disease. In 2008, the ARS scientists at the Wheat Genetics, Quality Physiology, and Disease Research Unit in Pullman, WA conducted long-term, mid-term, and short-term forecasts for stripe rust epidemics using the weather data, disease monitoring data, and cultivar resistance and sent stripe rust alerts to growers as early as in February and throughout the growing season. As a result of the accurate forecasting, timely alerts, and advice for choosing resistant cultivars and making decisions on whether or not to use fungicides, wheat growers implemented appropriate measures for stripe rust control. Major yield losses for the hard red winter wheat growing regions in Washington were prevented and multimillion dollar savings were realized by preventing unnecessary use of fungicides in many other regions. This research addresses NP303 (Plant Diseases) Component 2 (Biology, Ecology, Epidemiology, and Spread of Plant Pathogens and Their Relationships with Hosts and Vectors), Problem Statement 2C: Population Dynamics, Spread, and Epidemiology of Pathogens.
4. Identified new races of the stripe rust pathogen. Like many other pathogens, the stripe rust fungus is able to evolve into new virulent races that can circumvent non-race specific resistance in wheat and barley cultivars. In 2008, the ARS scientists at the Wheat Genetics, Quality Physiology, and Disease Research Unit in Pullman, WA completed identification of races of the stripe rust pathogen from samples collected throughout the United States in 2007 and determined predominant races. More importantly, we identified eleven new races; some of which are able to overcome resistance gene Yr17 that is currently used in many wheat breeding programs. We have sent the information to breeding programs, providing a warning for not using that gene alone. The finding of such new races will guide breeding programs to use durable type of resistance and/or combinations of effective major resistance genes to develop cultivars with durable resistance to stripe rust. This research addresses NP303 (Plant Diseases) Component 1 (Disease Diagnosis: Detection, Identification and Characterization of Plant Pathogens), Problem Statement 1B: Detection, Identification and Characterization, and Classification of Plant Pathogens; and Component 2 (Biology, Ecology, Epidemiology, and Spread of Plant Pathogens and Their Relationships with Hosts and Vectors), Problem Statement 2C: Population Dynamics, Spread, and Epidemiology of Pathogens.
5. Significant Activities that Support Special Target Populations
Advice on disease control was provided to growers through seminars, field talks, on-farm visits, phone conversation, and e-mails, which directly benefited growers and field consulting companies, many of which have small farms and business.
Jones, S.S., Lyon, S.R., Balow, K.A., Gollnick, M.A., Burns, J.W., Schillinger, W.F., Reisenauer, P.E., Murray, T.D., Chen, X., Garland Campbell, K.A., Morris, C.F., Goates, B. 2007. Registration of 'bauermeister' wheat. Crop Sci. 47:430-431.