Races of Puccinia striiformis f. sp. tritici in the United States in 2011 and 2012 and Comparison with Races in 2010

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most important diseases on wheat in the United States. In 2011, severe wheat stripe rust caused extensive application of fungicides in the western United States, and the disease was more widespread and caused more yield loss in the eastern United States in 2012. In this study, we characterized virulences and identified races of P. striiformis f. sp. tritici by testing the stripe rust samples collected throughout the United States in 2011 and 2012 on a set of 18 Yr single-gene differentials. In 2011, 35 races were identified from 349 viable samples collected from 19 states of the United States and Ontario province of Canada, with PSTv-11 (35.5%), PSTv-37 (12.6%), PSTv-14 (11.8%), PSTv-4 (5.4%), and PSTv-34 (3.4%) as the top five predominant races. In 2012, 23 races were identified from 341 viable samples collected from 24 states of the United States and Ontario of Canada, with PSTv-37 (47.5%), PSTv-11 (11.7%), PSTv-14 (10.0%), PSTv-52 (9.4%), and PSTv-48 (4.4%) as the top five predominant races. Nationally, PSTv-37, PSTv-52, and PSTv-34 were most widely distributed, while PSTv-11, PSTv-14, PSTv-4, and PSTv-48 were mostly detected in the western United States. High frequencies (>80%) were detected for virulences to Yr6, Yr7, Yr8, Yr9, Yr17, Yr27, Yr44, and YrExp2; moderate frequencies (20 to 80%) for virulences to Yr1, Yr43, YrTr1, and YrTye; low frequencies (<10%) for virulences to Yr10, Yr24, Yr32, and YrSP; and virulences to Yr5 and Yr15 were not detected, indicating that these two genes are still effective against the P. striiformis f. sp. tritici population in the United States. Both positive and negative associations were identified between some of the virulences. In total, 55 races identified from 2010 to 2012 in the United States were clustered into two major virulence groups, and dynamics of predominant races and virulence frequencies for the 3 years were presented and discussed. This information is useful for making decisions when screening wheat germplasm for developing stripe-rust-resistant wheat cultivars and managing the disease by growing cultivars with adequate and durable resistance. The severe epidemics and the occurrence of the large number of races in the 3 years indicate that efforts should be made to use diverse resistance genes, especially to combine effective all-stage resistance genes with genes for high-temperature adult-plant resistance.

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Virulence Characterization of Wheat Stripe Rust Fungus Puccinia striiformis f. sp. tritici in Ethiopia and Evaluation of Ethiopian Wheat Germplasm for Resistance to Races of the Pathogen from Ethiopia and the United States

Plant Disease ◽

10.1094/pdis-03-16-0371-re ◽

2017 ◽

Vol 101 (1) ◽

pp. 73-80 ◽

Cited By ~ 14

Author(s):

Anmin Wan ◽

Kebede T. Muleta ◽

Habtemariam Zegeye ◽

Bekele Hundie ◽

Michael O. Pumphrey ◽

...

Keyword(s):

United States ◽

Stripe Rust ◽

Puccinia Striiformis ◽

Rust Fungus ◽

Single Gene ◽

The United States ◽

Wheat Cultivars ◽

Low Frequencies ◽

Additional Information

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most important diseases of wheat in Ethiopia. In total, 97 isolates were recovered from stripe rust samples collected in Ethiopia in 2013 and 2014. These isolates were tested on a set of 18 Yr single-gene differentials for characterization of races and 7 supplementary differentials for additional information of virulence. Of 18 P. striiformis f. sp. tritici races identified, the 5 most predominant races were PSTv-105 (21.7%), PSTv-106 (17.5%), PSTv-107 (11.3%), PSTv-76 (10.3%), and PSTv-41 (6.2%). High frequencies (>40%) were detected for virulence to resistance genes Yr1, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, Yr27, Yr28, Yr31, Yr43, Yr44, YrExp2, and YrA. Low frequencies (<40%) were detected for virulence to Yr10, Yr24, Yr32, YrTr1, Hybrid 46, and Vilmorin 23. None of the isolates were virulent to Yr5, Yr15, YrSP, and YrTye. Among the six collection regions, Arsi Robe and Tiyo had the highest virulence diversities, followed by Bekoji, while Bale and Holeta had the lowest. Evaluation of 178 Ethiopian wheat cultivars and landraces with two of the Ethiopian races and three races from the United States indicated that the Ethiopian races were more virulent on the germplasm than the predominant races of the United States. Thirteen wheat cultivars or landraces that were resistant or moderately resistant to all five tested races should be useful for breeding wheat cultivars with resistance to stripe rust in both countries.

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Virulence Characterization of Puccinia striiformis f. sp. tritici Using a New Set of Yr Single-Gene Line Differentials in the United States in 2010

Plant Disease ◽

10.1094/pdis-01-14-0071-re ◽

2014 ◽

Vol 98 (11) ◽

pp. 1534-1542 ◽

Cited By ~ 89

Author(s):

Anmin Wan ◽

Xianming Chen

Keyword(s):

United States ◽

Stripe Rust ◽

Large Scale ◽

Puccinia Striiformis ◽

Yellow Rust ◽

Single Gene ◽

The United States ◽

The Past ◽

History Of

Puccinia striiformis f. sp. tritici causes stripe rust (yellow rust) of wheat and is highly variable in virulence toward wheat with race-specific resistance. During 2010, wheat stripe rust was the most widespread in the recorded history of the United States, resulting in large-scale application of fungicides and substantial yield loss. A new differential set with 18 yellow rust (Yr) single-gene lines was established and used to differentiate races of P. striiformis f. sp. tritici, which were named as race PSTv in distinction from the PST races identified in the past. An octal system was used to describe the virulence and avirulence patterns of the PSTv races. From 348 viable P. striiformis f. sp. tritici isolates recovered from a total of 381 wheat and grass stripe rust samples collected in 24 states, 41 races, named PSTv-1 to PSTv-41, were identified using the new set of 18 Yr single-gene differentials, and their equivalent PST race names were determined on the previous set of 20 wheat cultivar differentials. The frequencies and distributions of the races and their virulences were determined. The five most predominant races were PSTv-37 (34.5%), PSTv-11 (17.5%), PSTv-14 (7.2%), PSTv-36 (5.2%), and PSTv-34 (4.9%). PSTv-37 was distributed throughout the country while PSTv-11 and PSTv-14 were almost restricted to states west of the Rocky Mountains. The races had virulence to 0 to 13 of the 18 Yr genes. Frequencies of virulences toward resistance genes Yr6, Yr7, Yr8, Yr9, Yr17, Yr27, Yr43, Yr44, YrTr1, and YrExp2 were high (67.0 to 93.7%); those to Yr1 (32.8%) and YrTye (31.3%) were moderate; and those to Yr10, Yr24, Yr32, and YrSP were low (3.4 to 5.7%). All of the isolates were avirulent to Yr5 and Yr15.

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Effective Resistance to Wheat Stripe Rust in a Region with High Disease Pressure

Plant Disease ◽

10.1094/pdis-09-13-0909-re ◽

2014 ◽

Vol 98 (7) ◽

pp. 891-897 ◽

Cited By ~ 6

Author(s):

B. Bai ◽

J. Y. Du ◽

Q. L. Lu ◽

C. Y. He ◽

L. J. Zhang ◽

...

Keyword(s):

Stripe Rust ◽

Resistance Genes ◽

Rust Resistance ◽

Puccinia Striiformis ◽

Hot Spot ◽

Infection Type ◽

Durable Resistance ◽

Gansu Province ◽

Stripe Rust Resistance ◽

Adult Plant

Stripe rust is a major fungal disease of wheat. It frequently becomes epidemic in southeastern Gansu province, a stripe rust hot spot in China. Evaluations of wheat germplasm response are crucial for developing cultivars to control the disease. In total, 57 wheat cultivars and lines from Europe and other countries, comprising 36 cultivars with documented stripe rust resistance genes and 21 with unknown genes, were tested annually with multiple races of Puccinia striiformis f. sp. tritici in the field at Tianshui in Gansu province from 1993 to 2013. Seven wheat lines were highly resistant, with infection type (IT) 0 during the entire period; 16 were moderately resistant (IT 0;-2); and 26 were moderately susceptible (IT 0;-4), with low maximum disease severity compared with the susceptible control Huixianhong. ‘Strampelli’ and ‘Libellula’, with three and five quantitative trait loci, respectively, for stripe rust resistance have displayed durable resistance in this region for four decades. Ten cultivars, including ‘Lantian 15’, ‘Lantian 26’, and ‘Lantian 31’, with stripe rust resistance derived from European lines, were developed in our breeding program and have made a significant impact on controlling stripe rust in southeastern Gansu. Breeding resistant cultivars with multiple adult-plant resistance genes seems to be a promising strategy in wheat breeding for managing stripe rust in this region and other hot spots.

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Changes of Races and Virulence Genes in Puccinia striiformis f. sp. tritici, the Wheat Stripe Rust Pathogen, in the United States from 1968 to 2009

Plant Disease ◽

10.1094/pdis-12-16-1786-re ◽

2017 ◽

Vol 101 (8) ◽

pp. 1522-1532 ◽

Cited By ~ 21

Author(s):

Tinglan Liu ◽

Anmin Wan ◽

Dengcai Liu ◽

Xianming Chen

Keyword(s):

United States ◽

Stripe Rust ◽

Virulence Genes ◽

Puccinia Striiformis ◽

Yellow Rust ◽

Single Gene ◽

The United States ◽

Wheat Cultivars ◽

New Races ◽

Serious Disease

Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici, is a serious disease of wheat in the world. The obligate biotrophic fungal pathogen changes its virulence rapidly, which can circumvent resistance in wheat cultivars and cause severe epidemics. Because P. striiformis f. sp. tritici races have been identified in the United States using different wheat genotypes in different time periods, it is difficult to make direct comparisons of the current population with historical populations. The objective of this study was to characterize historical populations with 18 Yr single-gene lines that are currently used to differentiate P. striiformis f. sp. tritici races in order to understand virulence and race changes of the pathogen over 40 years in the United States. From 908 P. striiformis f. sp. tritici isolates collected from 1968 to 2009 in the United States, 171 races were identified and their frequencies were determined. More races, more new races, and races with more virulence genes were detected since the year 2000 than prior to 2000. None of the races were virulent to Yr5 and Yr15, indicating that these genes have been effective since the late 1960s. Virulence genes to the remaining 16 Yr genes were detected in different periods, and most of them increased in frequency over time. Some virulence genes such as those to Yr17, Yr27, Yr32, Yr43, Yr44, YrTr1, and YrExp2 appeared 14 to 37 years earlier than previously reported, indicating the greater value of using Yr single-gene lines as differentials. Positive and negative associations were detected between virulence genes. The continual information on virulence and races in the P. striiformis f. sp. tritici populations is useful for understanding the evolution of the pathogen and for breeding wheat cultivars with effective resistance to stripe rust.

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Wheat Stripe Rust Epidemics and Races of Puccinia striiformis f. sp. tritici in the United States in 2000

Plant Disease ◽

10.1094/pdis.2002.86.1.39 ◽

2002 ◽

Vol 86 (1) ◽

pp. 39-46 ◽

Cited By ~ 161

Author(s):

Xianming Chen ◽

Mary Moore ◽

Eugene A. Milus ◽

David L. Long ◽

Roland F. Line ◽

...

Keyword(s):

United States ◽

Stripe Rust ◽

Puccinia Striiformis ◽

Durable Resistance ◽

The United States ◽

Stripe Rust Resistance ◽

The South ◽

Wheat Stripe Rust ◽

South Central ◽

New Races

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is most destructive in the western United States and has become increasingly important in the south-central states. The disease has been monitored by collaborators through field surveys and in disease nurseries throughout the United States. In the year 2000, stripe rust occurred in more than 20 states throughout the country, which was the most widespread occurrence in recorded history. Although fungicide applications in many states reduced yield losses, the disease caused multimillion dollar losses in the United States, especially in Arkansas and California. One of the prevalent cultivars, RSI 5, had a yield loss of about 50% in the Sacramento-San Joaquin Delta region of California. In the Pacific Northwest, wheat losses due to stripe rust were minimal because cultivars with durable resistance were widely grown and the weather in May 2000 was not favorable for the disease. To identify races of the pathogen, stripe rust collections from 20 states across the United States were analyzed on 20 wheat differential cultivars, including Clement (Yr9, YrCle), Compair (Yr8, Yr19), and the Yr8 and Yr9 near-isogenic lines. In 2000, 21 previously identified races and 21 new races were identified. Of the 21 new races, 8 were pathotypes with combinations of virulences previously known to exist in the United States, and 13 had virulences to one or more of the lines Yr8, Yr9, Clement, or Compair. This is the first report of virulence to Yr8 and Yr9 in the United States. Most of the new races were also virulent on Express. Races that are virulent on Express have been identified in California since 1998. The races virulent on Yr8, Yr9, and Express were widely distributed in California and states east of the Rocky Mountains in 2000. The epidemic in 2000 demonstrates that increased efforts to breed for stripe rust resistance are needed in California, the south-central states, and some other states in the Great Plains. Diversification of resistance genes and use of durable resistance should prevent large-scale and severe epidemics.

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Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2004

Plant Disease ◽

10.1094/pd-90-1219 ◽

2006 ◽

Vol 90 (9) ◽

pp. 1219-1224 ◽

Cited By ~ 12

Author(s):

J. A. Kolmer ◽

D. L. Long ◽

M. E. Hughes

Keyword(s):

United States ◽

Leaf Rust ◽

Great Plains ◽

Resistance Genes ◽

Durable Resistance ◽

Puccinia Triticina ◽

Leaf Rust Resistance ◽

The United States ◽

Virulence Phenotype ◽

Common Phenotype

Collections of Puccinia triticina were obtained from rust-infected wheat leaves by cooperators throughout the United States and from surveys of wheat fields and nurseries in the Great Plains, Ohio Valley, southeast, California, and Pacific Northwest, in order to determine the virulence of the wheat leaf rust population in 2004. Single uredinial isolates (757 in total) were derived from the collections and tested for virulence phenotype on lines of Thatcher wheat that are near-isogenic for leaf rust resistance genes Lr1, Lr2a, Lr2c, Lr3a, Lr9, Lr16, Lr24, Lr26, Lr3ka, Lr11, Lr17a, Lr30, LrB, Lr10, Lr14a, Lr18, Lr21, and Lr28, and winter wheat lines with genes Lr41 and Lr42. In the United States in 2004, 52 virulence phenotypes of P. triticina were found. Virulence phenotype MCDSB, selected by virulence to resistance genes Lr17a and Lr26, was the most common phenotype in the United States and was found in all wheat growing areas. Virulence phenotype TBBGG, with virulence to Lr2a, was the second most common phenotype and was found primarily in the spring wheat region of the north-central states. Virulence phenotype MBDSB, which has virulence to Lr17a, was the third most common phenotype and was found in all wheat growing areas except California. Phenotype TNRJJ, with virulence to genes Lr9, Lr24, and Lr41, was the fourth most common phenotype and occurred in the southeastern states and throughout the Great Plains region. Virulence phenotypes avirulent to a second gene in the Thatcher differential line with Lr1 increased in frequency in the United States in 2004. The highly diverse population of P. triticina in the United States will continue to present a challenge for the development of wheat cultivars with effective durable resistance.

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First Report of Resistance of Wheat Line Avocet ‘S’ to Stripe Rust Caused by Puccinia striiformis f. sp. tritici (Pst) in Syria

Plant Disease ◽

10.1094/pdis-11-12-1109-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 996-996 ◽

Cited By ~ 5

Author(s):

K. Nazari ◽

R. El Amil

Keyword(s):

Stripe Rust ◽

Resistance Genes ◽

Puccinia Striiformis ◽

Geographical Area ◽

Adult Plant ◽

Recurrent Parent ◽

Post Inoculation ◽

Differential Cultivar ◽

Infection Types ◽

Original Area

Seedling assays and field-based assessments are common approaches used in monitoring pathogenic variability of Puccinia striiformis f. sp. tritici (Pst). Due to the many candidate genes for resistance, and the occasional presence of uncharacterized or unexpected resistance genes, interpretation of seedling and adult plant responses of stripe rust differential genotypes can be confounded. To facilitate data interpretation and overcome growth habit differences, a set of near-isogenic lines (NILs) based on a susceptible selection of the widely susceptible Australian spring wheat cultivar Avocet was developed in Plant Breeding Institute, University of Sydney. During the 2011 rust survey of major wheat growing areas in Syria, we collected and recovered two isolates, one from bread wheat and one from durum, using susceptible cultivar Morocco. Fresh urediniospores collected from inoculated seedlings of cultivar Morocco under greenhouse conditions were used to infect a differential set of seedlings comprising the Avocet S NIL series with Yr1, 5, 6, 7, 8, 9, 10, 15, 17, 27, 32, A, SP and a supplementary set of Kalyansona (Yr2), Fielder (Yr6, Yr20), Thatcher (Yr7), Federation*4/Kavkaz (Yr9), TP1295 and TP981 (Yr25), Ciano 79 and Opata 85 (Yr27), Lemhi (Yr21), Anza (YrA), Tres/6*Avocet ‘S’, Cook, Avocet S, and Federation following standard protocol (1). Seedling infection types (IT) were recorded 15 to 17 days post-inoculation using a 0, ;(fleck), 1 to 4 scale, with ITs 3 and 4 considered to be high. According to European race nomenclature (1), these isolates would be classified as 6 E0 and assumes that differential cultivars Lee (Yr7) and Heines Kolben should be susceptible. A low infection of ;N (necrotic areas without sporulation) was observed on Avocet S and Avocet NILs Yr1, 5, 8, 10, 15, 17, 32, A, and SP. NILs Yr6, 7, and 9 responded with high infection types. Among the supplementary set, IT ;N was recorded for Anza, Cook, Tres/6*Avocet S, Opata 85, and Ciano 79 whereas IT 3+4 occurred on Kalyansona, Fielder, Thatcher, Federation*4/Kavkaz, TP1295 and TP981, and Lemhi. Federation and Morocco were susceptible to both isolates. Based on these data we concluded that 1) Avocet S carries at least one effective gene for resistance to the two isolates (temporarily designated as YrAvS and perhaps the same as the gene(s) in Anza and Cook); and 2) since Avocet S was resistant, it was expected that all the NILs should also be resistant unless one of the selected resistance genes was closely linked in repulsion with the gene in Avocet S. Since such a situation is possible for only one line, other explanations are that the recurrent parent, Avocet S, was not genetically homogeneous, or more likely, that the genetic background of Avocet S was not fully regenerated during the six backcross and subsequent selfing generations. This work illustrates the problems that can arise when sets of differential genotypes that perform in a satisfactory way in a particular (limited) geographical area are applied globally. Pst races carrying avirulence genes that are not present in the original area where a differential cultivar is characterized for its susceptibility may be present in other areas. Consequently, a differential cultivar which was susceptible in the original area may unexpectedly exhibit resistance in a new region. Therefore, host lines considered to be “universally susceptible” in one region may not be susceptible globally. The resistance of Avocet S is yet to be characterized. Reference: (1) R. Johnson et al. Trans. Br. Mycol. Soc. 58:475, 1972.

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Quantitative Trait Loci Mapping of Adult Plant and Seedling Resistance to Stripe Rust (Puccinia striiformis Westend.) in a Multiparent Advanced Generation Intercross Wheat Population

Frontiers in Plant Science ◽

10.3389/fpls.2021.684671 ◽

2021 ◽

Vol 12 ◽

Author(s):

Sandra Rollar ◽

Manuel Geyer ◽

Lorenz Hartl ◽

Volker Mohler ◽

Frank Ordon ◽

...

Keyword(s):

Stripe Rust ◽

Resistance Genes ◽

Quantitative Trait ◽

Rust Resistance ◽

Puccinia Striiformis ◽

Stripe Rust Resistance ◽

Adult Plant ◽

Seedling Resistance ◽

Wheat Population ◽

Advanced Generation

Stripe rust caused by the biotrophic fungus Puccinia striiformis Westend. is one of the most important diseases of wheat worldwide, causing high yield and quality losses. Growing resistant cultivars is the most efficient way to control stripe rust, both economically and ecologically. Known resistance genes are already present in numerous cultivars worldwide. However, their effectiveness is limited to certain races within a rust population and the emergence of stripe rust races being virulent against common resistance genes forces the demand for new sources of resistance. Multiparent advanced generation intercross (MAGIC) populations have proven to be a powerful tool to carry out genetic studies on economically important traits. In this study, interval mapping was performed to map quantitative trait loci (QTL) for stripe rust resistance in the Bavarian MAGIC wheat population, comprising 394 F6 : 8 recombinant inbred lines (RILs). Phenotypic evaluation of the RILs was carried out for adult plant resistance in field trials at three locations across three years and for seedling resistance in a growth chamber. In total, 21 QTL for stripe rust resistance corresponding to 13 distinct chromosomal regions were detected, of which two may represent putatively new QTL located on wheat chromosomes 3D and 7D.

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Genotyping Puccinia striiformis f. sp. tritici Isolates with SSR and SP-SNP Markers Reveals Dynamics of the Wheat Stripe Rust Pathogen in the United States from 1968 to 2009 and Identifies Avirulence Associated Markers

Phytopathology ◽

10.1094/phyto-01-21-0010-r ◽

2021 ◽

Author(s):

Tinglan Liu ◽

Qing Bai ◽

Meinan Wang ◽

Yuxiang Li ◽

Anmin Wan ◽

...

Keyword(s):

United States ◽

Stripe Rust ◽

Puccinia Striiformis ◽

Genetic Relationships ◽

Genotypic Diversity ◽

The United States ◽

Snp Markers ◽

Avirulence Genes ◽

Introduced Populations ◽

The Us

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of wheat in the United States. The fungal pathogen can rapidly evolve, producing new virulent races infecting previously resistant cultivars and genotypes adapting to different environments. The objective of this study was to investigate the long-term population dynamics of Pst in the US. Through genotyping 1,083 isolates of 1968 to 2009 using 14 simple sequence repeat (SSR) markers and 92 secreted protein single nucleotide polymorphism (SP-SNP) markers, 614 and 945 genotypes were detected, respectively. In general, the two types of markers produced consistent genetic relationships among the Pst populations over the 40 years. The prior 2000 and 2000-2009 populations were significantly different, and the latter showed higher genotypic diversity and higher heterozygosity than the former populations. Clustering analyses using genotypes of either SSR and SP-SNP markers revealed three molecular groups (MGs), of which MG1 and MG2 existed in both the prior 2000 and 2000-2009 populations while MG3 mainly emerged in 2000 to 2009. Some of the isolates in the period of 2000-2009 formed individual clusters, suggesting exotic incursions; whereas other isolates of the same period were clustered together with prior-2000 isolates, indicating that they were developed from the previously established populations. The data suggest the co-existence of newly introduced populations with established populations in the United States. Twenty SP-SNP markers were significantly associated to individual avirulence genes. The results are useful for developing more accurate monitoring systems and provides guidance for the disease management.

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Challenges and solutions for stripe rust control in the United States

Australian Journal of Agricultural Research ◽

10.1071/ar07045 ◽

2007 ◽

Vol 58 (6) ◽

pp. 648 ◽

Cited By ~ 115

Author(s):

X. M. Chen

Keyword(s):

Stripe Rust ◽

Puccinia Striiformis ◽

Natural Infection ◽

The United States ◽

Adult Plant ◽

Field Surveys ◽

Breeding Lines ◽

South Central ◽

Eastern Usa ◽

New Races

Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici, has been one of the most destructive diseases on wheat in the western USA since the late 1950s and has become increasingly important in the central and south-eastern USA since 2000. Stripe rust of barley, caused by P. striiformis f. sp. hordei, a relatively new disease, has established and caused severe damage in the south-central and western states since the pathogen was first reported in Texas in 1991. Stripe rusts of wheat and barley have been monitored by trap nurseries and by field surveys. Collections of stripe rust from wheat, barley, triticale, and grasses have been tested on a set of 20 wheat differential genotypes for identifying races of P. striiformis f. sp. tritici and a set of 12 barley differential genotypes for identifying races of P. striiformis f. sp. hordei. In total, 62 new races of P. striiformis f. sp. tritici and 22 new races of P. striiformis f. sp. hordei have been identified since 2000. Germplasm and breeding lines of wheat and barley have been tested every year under natural infection in the field and with selected races in the greenhouse. Combinations of durable high-temperature, adult-plant resistance with effective all-stage resistance should provide more effective stripe rust control and reduce the use of fungicides.

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