Items from the United States - Washington.

ITEMS FROM THE UNITED STATES

 

WASHINGTON

 

USDA-ARS, WHEAT GENETICS, QUALITY, PHYSIOLOGY AND DISEASE RESEARCH UNIT

361 Johnson Hall, Washington State University, P. O. Box 646430, Washington State University, Pullman, WA 99164, USA.

 

Epidemiology and control of wheat stripe rust in the United States, 2005. [p. 192-195]

Xianming Chen, David A. Wood, Laura Penman, Paul Ling, Meinan Wang, and Feng Lin.

Monitoring rusts, predicting epidemics, assessing yield losses and implementing disease control. In 2005, stripe rust, leaf rust, stem rust, and other foliar diseases of wheat were closely monitored throughout the Pacific Northwest (PNW) through field surveys and disease nurseries. Early prediction of wheat stripe rust epidemic was made using rust forecasting models based on temperatures in December 2004 and January 2005. The warmer-than-normal winter allowed more survival of the stripe rust fungus in infected leaf tissues, resulting in early occurrence and quick development of stripe rust in the PNW. Based on the forecast, a stripe rust alert was sent to wheat workers and growers as early as in February 2005, which allowed growers to be prepared for control of stripe rust by planting resistant spring wheat cultivars and using fungicides. In March 2005, field surveys were conducted periodically and rust updates on distribution and severity were provided to growers based on real-time rust situations. The early occurrence of stripe rust due to the warm winter and fast development due to the disease-favorable weather conditions (cool and frequent precipitations) in the late spring and early summer made the disease pressure unusually high. Advice on whether or not to use fungicides on specific cultivars and timely use of fungicides were provided to growers for minimizing yield losses and fungicide usage and maximizing profit under the severe stripe rust epidemic. The effective control of stripe rust saved the PNW wheat growers millions of dollars that could have been lost without the timely control of the disease. Based on acreages of planted resistant and susceptible cultivars and fungicide applications in the commercial fields, and data of our experimental plots, the yield losses caused by stripe rust were reduced to 2 % for the winter crop and 4 % for the spring crop in the state of Washington. Without fungicide application, the winter wheat crop could have suffered 5-10 % yield losses and the spring wheat crop could have suffered 15-20 % yield losses, and individual fields grown with susceptible cultivars could have had 40-60 % yield losses.

Through cooperators in many other states, wheat stripe rust was monitored throughout the United States. In 2005, wheat stripe rust occurred in at least 35 states, which was the most widespread of the disease in the recorded U.S. history. Severe epidemics occurred in California, Texas, Louisiana, Arkansas, Oklahoma, Colorado, Nebraska, Kansas, Alabama, Indiana, Missouri, and some other states in the southeast and Great Plains, and the PNW including southern Idaho, where stripe rust epidemic did not occur from 2000 to 2004.

In 2005, leaf rust, which was severe in the eastern and Great Plains states, occurred severely in our experimental plots in western Washington and in some irrigated fields in eastern Washington. The wide application of fungicides for controlling stripe rust also reduced the risk of leaf rust. Stem rust was found in limited field spots in the late growth stage in eastern Washington, and it did not cause significant damage.

The epidemic impact and benefit of fungicide control were assessed based on our experimental data and disease surveys. In 2005, we evaluated yield reduction by stripe rust and yield increase by fungicide application with 24 winter wheat and 16 spring wheat cultivars in field experiments of a randomized split-block design with 4 replications. Yield losses caused by stripe rust were more than 70 % on highly susceptible winter wheat and more than 60 % on highly susceptible spring wheat. Fungicide spray increased yield by 2.9 times for susceptible winter cultivars and by 1.6 times for susceptible spring wheat cultivars.

Identifying races of Puccinia striiformis f. sp tritici. Because the most widespread of stripe rust, we collected and received 518 samples from 28 states for identification of stripe rust races in 2005. Of the samples that were collected from wheat, barley, triticale, and grasses, 477 were wheat stripe rust. The stripe rust samples were tested on a set of 20 wheat differential cultivars to identify races of the pathogen. A total of 29 races were detected, of which seven were first identified in 2005. Previously identified races counted for 94 % and new races counted for 6 % of the isolates. The new group of races, which have virulences on resistance genes Yr8 and Yr9 and were first detected in the US in 2000, counted for 96 %, whereas the old group of races, which are avirulent on Yr8 and Yr9, counted for only 4 % of the isolates. The three most predominant races in the U.S. in 2005 were PST-100 (33 %), PST-102 (27 %), and PST-115 (14 %). PST-100 has virulences on Lemhi, Heines VII, Produra, Yamhill, Stephens, Lee, Fielder, Express, Yr8, Yr9, Clement, and Compair of the 20 differential cultivars. PST-102, which was first detected in 2003, has all virulences of PST-100 plus virulence on Tres. PST-115, which was first detected in 2004, has all virulences of PST-102 plus virulence on Paha. Some new races had even wider spectra of virulence. For example, PST-116, which was limited to the PNW in 2005, had all virulences of PST-115 plus virulences on Moro. The increases of these races in frequency and appearance of new races circumvented the all-stage (also called seedling) resistance in winter wheat cultivars such as Eltan and Hiller and several spring wheat cultivars such as Hank, WPB 926, Tara, IDO377s, and Jefferson. These races will likely cause problems in the near future. Cultivars with race nonspecific high-temperature, adult-plant resistance continued to be the best.

Genomic study of P. striiformis and its relationships to other cereal rusts. To identify stripe rust genes, we constructed a bacterial artificial chromosomal (BAC) library and a full-length cDNA library from spores of race PST-78 of the wheat stripe rust pathogen. This race represents the group of new races that were first identified in the year 2000 and have caused the widespread epidemics in the U.S. since 2000. The full-length cDNA library consisted of 42,240 clones with an average cDNA insert of 1.5 kb. A total of 167 randomly picked full-length cDNA clones were sequenced, of which 126 had complete sequences and 41 had partial sequences. The BLAST (Basic Local Alignment Search Tool) program was used to compare the sequences to the fungal gene sequence database in NCBI (the National Center for Biotechnology Information). Functions of 36 genes were identified based on their significantly high homologies with genes having clear identified functions in other fungi. These genes included the elongation factor, mitogen-activated protein kinase (MAPK), deacetylase, calnexin, transaldolase, TATA binding protein, UDP-glucose dehydrogenase, b-tubulin, diacylglycerol acyltransferase, retinoblastoma binding protein, GTPase Rac1, serine/threonine kinase receptor, iron-sulfur cluster Isu1-like protein, and enolase. A total of 128 ORFs were identified from the sequences of the 167 cDNA clones. The longest ORF had 951 bp, and the shortest ORF had 93 bp. The genes for elongation factor, TATA-box binding protein, beta-tubulin, nucleoside diphosphate kinase (NDK), and mitogen-activated protein kinase were used to determine evolutionary relationships of the stripe rust pathogen to other fungi. The wheat stripe rust pathogen was more related to the wheat stem rust pathogen based on the elongation factor genes than to any other fungal species. Fungal species in Basidiomycetes were more related to each other than to fungi in other groups.

To use the identified genes of the wheat stripe rust pathogen in study of the pathogen population structures and variations, a total of 18 specific DNA primers were designed based on the DNA sequences of 16 selected genes with clear functions. Primers based on genes encoding for the differentiation-related protein (Pstc30M9), spore formation protein (Pstc10I12), MAPK (Pstc55B10) and deacetylase (Pstc10C3) were used to identify polymorphisms among seven cereal rust species or formae speciales: the wheat stripe rust, barley stripe rust, bluegrass stripe rust, orchard grass stripe rust, wheat stem rust, wheat leaf rust, and barley leaf rust pathogens. The primers for the MAPK gene (Pstc55B10F/R) and deacetylase gene (Pstc10C3) amplified the same size of DNA fragments from the genomic DNAs of the wheat stripe rust and barley stripe rust isolates, but did not amplify any fragment from other stripe rust forms and other rust species, indicating that these primers are useful in separating the wheat and barley stripe rusts from other rusts, and that both wheat and barley stripe rust forms are more closely related to each other than to other stripe rust forms and other rust pathogens. Some of the EST primers were able to separate different formae speciales of P. striiformis and isolates of P. striiformis f. sp. tritici.

Evaluation of wheat germ plasm and screening breeding lines for resistance to stripe rust and other foliar diseases. In 2005, we evaluated more than 6,900 winter wheat and 9,100 spring wheat entries for resistance to stripe rust and other foliar diseases. The entries included germplasm, genetic populations, and breeding lines from the National Germplasm Collection Center, and public and private breeding programs. All nurseries were evaluated at both Pullman and Mt. Vernon locations under natural stripe rust infection. The wheat entries also were evaluated for resistance to leaf rust, powdery mildew, and physiological leaf spot at the Mt. Vernon field plots, where these diseases occurred. Some of the nurseries were also tested in the greenhouse with selected five races of stripe rust covering all identified virulences for further characterization of resistance. Disease data of regional nurseries were provided to all breeding and extension programs of that region, while data of individual breeders' nurseries were provided to the individual breeders. Through our testing, new wheat cultivars such as Bauermeister (WA7939), MDM (WA7936), Concept (89*88D), George (GMG-Q-1), Rjames (GMG-Q2), Eddy (BZ9W96-788-E), and Sola (DA900-229) have been or are being released.

Through germ plasm screening, we have established a core collection of wheat germ plasm with stripe rust resistance. The current collection has more than 5,000 entries, which will be valuable sources of stripe rust resistance for further characterization of resistance, identified new effective resistance genes, and for development of wheat cultivars with superior resistance.

Genetic study of resistance, molecular mapping, and cloning stripe rust resistance genes. To identify genes for resistance and develop molecular markers for the resistance genes, we made crosses among Alpowa, Express, IDO377s, and Zak and Avocet Susceptible (AVS). In 2005, F5 progeny and parents of these crosses were evaluated in the field for resistance to stripe rust. Parents and F1, F2, and F3 progeny from the AVS/Express cross were tested in the greenhouse with selected races of the wheat stripe rust pathogen. The results showed that Express had a dominant gene for all-stage resistance to stripe rust. Using the resistance gene-analog polymorphism (RGAP) technique and the field data of the 'AVS/Alpowa' cross, a linkage group was constructed for a quantitative trait locus conferring high-temperature, adult-plant resistance in Alpowa. Through collaboration with Dubcovsky at UC Davis, we identified a new gene and named it Yr36 from T. turgidum subsp. dicoccoides controlling HTAP resistance. We have made significant progress in cloning Yr5, a resistance gene effective against all wheat stripe rust races identified so far in the U.S., using the BAC library we have recently constructed. We have identified positive BAC clones and subclones using the molecular markers we identified for Yr5.

Determine effectiveness and use of fungicides for rust control. A total of 10 fungicide treatments were evaluated for controlling stripe rust in experimental fields near Pullman, WA. Susceptible winter wheat cultivar PS 279 was planted on 14 October, 2004, and susceptible spring wheat cultivar Fielder and moderately susceptible Eden were planted on 19 April, 2005, using a completely randomized block design with four replications. The fungicide treatments were compared with non-treatment check. Fungicides were sprayed on 21 May in the winter wheat plots when the plants were at the late jointing stage with 20-40 % stripe rust severity, and on 20 June in the spring wheat plots when the plants also were at the late jointing stage with 20-40 % stripe rust severity. Severities of stripe rust were recorded five times for the winter plots and four times for the spring plots at and after fungicide application. Area under disease progress curve (AUDPC) was calculated for each treatment and the check from the multiple sets of rust severity data, and also used for comparison of rust severities over the time period. Test weight and yield were recorded for each plot at the time of harvesting. All fungicide treatments significantly reduced rust severity and increased yield compared to the untreated check. All treatments also increased test weight, but only treatments of two applications of Quilt, Absolute, Sparta, and Folicur significantly increased test weight of PS 279; only Sparta, Quilt, Absolute, and Folicur significantly increased test weight of Fielder; and all treatments but Absolute significantly increased test weight of Eden. These treatments varied in duration of effectiveness, which was correlated with relative stripe rust AUDPC and yield. Based on rust AUDPC data, the best treatments were two applications of Quilt, Absolute, and Folicur for winter wheat PS 279; Absolute, Folicur, Sparta, Quilt, Flutriafol, and Tilt for spring wheat Fielder; and all treatments were not significantly different from each other for the moderately susceptible cultivar, Eden. Based on yield data, Absolute, Sparta, two applications of Quilt, and Folicur were the best in the tests with PS 279; Sparta, Quit, Absolute, Folicur, and Stratego were the best in the test with Fielder; and all fungicide treatments were not significantly different from each other in the tests with moderately susceptible Eden.

Compared to the disease and yield data of 2004, the 2005 data validated two applications of fungicides under the circumstances of early starting and prolonged epidemics like in 2005. In 2004, stripe rust severity was only 1 % on PS 279 on 6 June when fungicides were applied at the boot stage. Untreated plot produced 66 bu/acre and the best controlled plot (with two applications of Quilt) produced 110 bu/acre. In contrast, in 2005 stripe rust severity had already reached 40 % on 21 May when fungicides were used at the late jointing stage. The untreated plot of PS 279 produced only 13 bu/acre and the same treatment (two applications of Quilt) produced 45 bu/acre.

 

Publications. [p. 195-196]

  • Amand PS, Guttieri MJ, Hole D, Chen XM, Brown-Guedlera G, and Souza EJ. 2005. Preliminary QTL analysis of dwarf bunt and stripe rust resistance in a winter wheat population. PAGXII Abstracts, p. 155.
  • Blount AR, Rizvi S, Barnett RD, Chen XM, Schubert TS, Dankers WH, Momol TM, and Dixon WN. 2005. First report of stripe rust (Puccinia striiformis Westend. f. sp. tritici Eriks.) on wheat (Triticum aestivum L.) in north Florida. Online: Plant Health Progress (http://www.plantmanagementnetwork.org/pub/php/brief/2005/stripe/).
  • Campbell KG, Allan RE, Anderson J, Pritchett JA., Little LM, Morris CF, Line RF, Chen XM, Walker-Simmons MK, Carter BP, Burns JW, Jones SS, and Reisenauer PE. 2005. Registration of 'Finch' winter wheat. Crop Sci 45:1656-1657.
  • Campbell KG, Allan RE, Anderson J, Pritchett J, Little LM, Morris CF, Line RF, Chen XM, Walker-Simmons MK, Carter BP, Burns JW, Jones SS, and Reisenauer PE. 2005. Registration of 'Chukar' winter club wheat. Crop Sci 45:1657-1659.
  • Carter A, Hansen J, Koehler T, Chen XM, and Zemetra R. 2005. Development of a recombinant inbred line (RIL) population in soft white winter wheat. Agron Abstr on-line at: http://crops.confex.com/crops/2005am/techprogram/P7964.HTM.
  • Chen XM. 2005. Challenges and solutions for stripe rust control in the United States. In: Abstr 'Global Landscapes', Cereal Rust Control Conf, University of Sydney, Australia, 20-22 September. P. 45.
  • Chen XM. 2005. Epidemiology and control of stripe rust on wheat. Can J Plant Pathol 27:314-337.
  • Chen XM, Ling P, and Wang MN. 2005. Identification of genes in the stripe rust pathogen (Puccinia striiformis) and use of gene-specific primers to determine evolutionary relationships among formae speciales of P. striiformis with other fungi. In: Abstr 'Global Landscapes', Cereal Rust Control Conf, University of Sydney, Australia, 20-22 September. P. 51.
  • Chen XM and Penman L. 2005. Stripe rust epidemic and races of Puccinia striiformis in the United States in 2004. Phytopath 95:S19.
  • Chen XM and Wood DA. 2005. Control of stripe rust of spring barley with foliar fungicides, 2004. Fung & Nemat Tests 60:CF020.
  • Chen XM and Wood DA. 2005. Control of stripe rust of spring wheat with foliar fungicides, 2004. Fung & Nemat Tests 60:CF021.
  • Chen XM and Wood DA. 2005. Control of stripe rust of winter wheat with foliar fungicides, 2004. Fung & Nemat Tests 60:CF027.
  • Chen XM, Wood DA, Penman L, and Ling P. 2005. Epidemiology and control of wheat stripe rust in the United States, 2004. Ann Wheat Newslet 51:240-242.
  • Chen XM, Wood D, Penman L, Ling P, and Wang MN. 2005. Stripe rust epidemics and control in the United States from 2000 to 2004. Agron Abstr on-line at: http://crops.confex.com/crops/2005am/techprogram/P7989.HTM.
  • Chen XM, Wood DA, Penman L, Ling P, and Yan GP. 2005. Control of stripe rusts of wheat and barley. In: 2005 Field Day Abstracts, Highlights of Research Progress, Department of Crop and Soil Sciences. Pp. 39-40.
  • Kidwell KK, Santra DK, Uauy C, Chen XM, Campell KG, and Dubcovsky J. 2005. Identifying and utilizing high-temperature adult-plant resistance to combat stripe rust in wheat. In: Stripe Rust of Wheat: A Plan for Recovery Symp, Agron Abstr on-line at http://crops.confex.com/crops/2005am/techprogram/S1277.HTM.
  • Ling P and Chen XM. 2005. Construction of a hexaploid wheat (Triticum aestivum L.) bacterial artificial chromosome library for cloning genes for stripe rust resistance. Genome 48:1028-1036.
  • Ling P, Chen XM, Le DQ, and Campbell K.G. 2005. Construction of BAC and full-length cDNA libraries for genomic analysis of the wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici). PAGXIII Abstr P. 94.
  • Ling P, Chen XM, Le DQ, and Campbell KG. 2005. Towards cloning of the Yr5 gene for resistance to wheat stripe rust. PAGXIII Abstr, p. 97.
  • Loladze A, Campbell KG, and Chen XM. 2005. Development of a detached leaf assay for stripe rust resistance screening. Agron Abstr on-line at http://crops.confex.com/crops/2005am/techprogram/P3298.HTM.
  • Pahalawatta V and Chen XM. 2005. Genetic analysis and molecular mapping of wheat genes conferring resistance to the wheat stripe rust and barley stripe rust pathogens. Phytopath 95:427-432.
  • Pahalawatta V and Chen XM. 2005. Inheritance and molecular mapping of barley genes conferring resistance to wheat stripe rust. Phytopath 95:884-889.
  • Santra D, Santra M, Watt C, Uauy C, Kidwell KK, Chen XM, Dubcovsky J, and Campbell KG. 2005. Mapping QTL for high temperature adult plant resistance to stripe rust in wheat (Triticum aestivum L.). Agron Abstr on-line at http://crops.confex.com/crops/2005am/techprogram/P4381.HTM.
  • Uauy C, Brevis JC, Chen XM, Khan IA, Jackson LF, Chicaiza O, Distelfeld A, Fahima T, and Dubcovsky J. 2005. High-temperature adult plant (HTAP) stripe rust resistance gene Yr36 from Triticum turgidum ssp. dicoccoides is closely linked to the grain protein content locus Gpc-B1. Theor Appl Genet 112:97-105.