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Puccinia striiformis f. sp. tritici (Pst) causes wheat stripe rust (also called yellow rust, Yr), one of the most important diseases worldwide. Characterization of virulence in Pst populations is essential for developing wheat cultivars with effective and durable resistance to control the disease. A total of 138 Pst races, including 120 races that were not previously reported, were identified from stripe rust collections made from Canada, China, Ecuador, Egypt, Italy and Mexico in 2013–2020 using a set of 18 Yr single-gene differentials. Virulence of the resistance gene Yr5 or Yr15 was not found in isolates from any of the countries, indicating their effectiveness against the Pst populations. Virulence to 16 Yr genes was detected, but the frequencies varied greatly among countries. On average, the frequencies of virulence to Yr6, Yr7, Yr9, Yr43, Yr44 and YrExp2 were high (81.7–90.6%), those to Yr1, Yr8, Yr17, Yr27, YrSP and Yr76 were moderate (34.0–56.8%), and those to Yr10, Yr24, Yr32 and YrTr1 were low or very low (0.4–18.5%). The same races detected in different countries and different races from different countries clustered into the same virulence groups, indicating Pst migration among different countries, especially between eastern Asia and the Mediterranean region. These results should be useful for breeding wheat cultivars with effective resistance to stripe rust in these countries as well as globally. [ABSTRACT FROM AUTHOR]

Stripe (yellow) rust, caused by the biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is emerging as a serious threat to wheat (Triticum aestivum L.) production in many regions of North America. Genetic resistance to stripe rust is typically conditioned by the products of resistance genes that detect pathogen-associated molecular patterns and initiate a cascade of signalling events, culminating in the generation of reactive oxygen species (ROS) and a hypersensitive response (HR) that eventually suppress the pathogen. Complete resistance with no symptoms (immunity response) has also been observed, but less frequently, in certain Pst-wheat interactions. However, such HR-independent resistance responses to Pst have not been well studied. Here we report that the Pst-resistant near isogenic line Avocet-Yr15 (carrying the Yr15 resistance gene) exhibited an immunity response to an isolate of Pst collected in Elora, Ontario, while the Avocet-S line (lacking Yr15) was highly susceptible to the same isolate. In particular, histochemical assays of defence-associated ROS generation and HR were negative during the early stages of the interaction between Pst and the resistant Avocet-Yr15. Microscopic analysis indicated that the pathogen was not able to penetrate the stomata of Avocet-Yr15. Moreover, RNA-sequencing of the immunity response of Avocet-Yr15 to Pst highlighted the activation of a global anti-oxidative-stress response consisting of genes involved in the maintenance of cell viability, redox homoeostasis and photosynthesis. These results provide insights into the molecular mechanisms controlling the immunity response to stripe rust of wheat. [ABSTRACT FROM AUTHOR]

Stripe rust (yellow rust), caused by Puccinia striiformis Westend. f. sp. tritici (Pst), is one of the most destructive fungal disease in wheat(Triticum aestivum L.). Growing resistant cultivars is the best strategy to control stripe rust. The wheat introgression line H9015-17-1-9-6 was developed from an interspecific hybridization between the common wheat cultivar 7182 and Psathrostachys huashanica Keng (2n = 2x = 14, NsNs). H9015-17-1-9-6 has all-stage resistance to all known Chinese stripe rust races, including three widely virulent races: CYR32, CYR33 and CYR34. To identify stripe rust resistance genes in the introgression line, H9015-17-1-9-6 was crossed with the susceptible genotype 'Mingxian169' and the F1, F2, F3 and BC1 generations were inoculated with Pst races under controlled greenhouse conditions. The results indicated that a single dominant gene in H9015-17-1-9-6, temporarily designated as YrH9015, confers resistance to race CYR32. Using bulked segregant analysis methods, we identified seven resistance gene analogue polymorphism (RGAP) markers and three simple sequence repeat (SSR) markers associated with YrH9015 on the long arm of chromosome 5D. The genetic distances of the two closest flanking markers, namely M4 and M5, were 2.4 and 3.1 centimorgans, respectively. Based on the chromosomal location, reaction patterns and pedigree analysis, YrH9015 is likely a novel resistance gene. This gene and the flanking markers obtained from this study are expected to be useful in pyramiding YrH9015 with other Yr genes to develop wheat cultivars with high-level and durable resistance to stripe rust and may also benefit marker assisted selection (MAS) in breeding programmes. [ABSTRACT FROM AUTHOR]

Stripe rust of wheat (Triticumspp. L.) is an emerging problem in western Canada. The causal pathogen (Puccinia striiformisf. sp.triticiEriks.) has the potential to overwinter, which is a concern because of green bridging leading to earlier establishment of rust epidemics. Resistance conferred by seedling/all-stage and adult plant genes is the most effective approach to manage this disease. However, many Canadian wheat varieties lack seedling or all-stage resistance. The effectiveness ofYrgenes under field conditions was assessed by exposing differentials/varieties carryingYrgenes to natural inoculum in multiple environments. The differentials were planted at multiple Saskatchewan locations in 2013, 2014 and 2016 and significant stripe rust was detected at 12 site-years. Additionally, 33 winter wheat varieties and advanced breeding lines were assessed for stripe rust reaction in 2016 at Swift Current, Saskatchewan. Disease severity was assessed on flag and penultimate leaves between early milk to soft dough growth stages. The genesYr5,Yr15, YrSPand those in ‘Yamhill’ are effective in Saskatchewan under field conditions. Genes/differentials were classified into two major groups based on cluster analysis, one with defeated genes and the other with partial resistant genes. GenesYrA,Yr6, Yr7,Yr8, Yr9,Yr27, Yr29,Yr31, Yr32andYrSuwere not effective in the field to SK races. At Swift Current, winter wheat varieties/lines carryingYr17were resistant in the field, whereas those carryingYr10were not. [ABSTRACT FROM PUBLISHER]

The article provides information on Radiant hard red winter wheat. The winter wheat demonstrated well adaptation to the Canadian prairies and non-hazard region. The features of the winter wheat include good winter survival, strong straw, late maturity, high test weight, large seeds, moderate height, and good stripe rust resistance. The winter wheat's pedigree and breeding method, performance, and breeder seed maintenance and distribution are discussed.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (PST), has historically been the most frequently destructive disease of wheat (Triticum aestivum) in the western United States and has become a more frequent problem in the central and southeastern states since 2000. The race composition of PST has been determined every year from rust-infected leaf samples of wheat and grasses collected in the United States on a set of 20 differential wheat genotypes. In 2006, a total of 18 races were detected, of which five were detected for the first time. In 2007, a total of 30 races were detected, of which 11 were newly detected. Among the 16 new races detected in 2006 and 2007, PST-127 was the most important as it has the broadest virulence spectrum identified so far (virulent to all 20 differential genotypes except for 'Moro', AVS/6*Yr5 (Yr5), and 'Tres') and combined virulence factors to 'Tyee' (YrTye) and 'Hyak' (Yr17 and YrTye) and those common in the race group detected since 2000. The distribution, frequency changes, and evolutionary relationships for races detected from 2000 to 2007 were analyzed. Three major waves of race changes were identified during the eight-year period. From 2000 to 2002, the predominant races were PST-78 and PST-80, which were virulent on wheat genotypes 'Lemhi', 'Heines VII', 'Lee', 'Fielder', 'Express', AVS/6*Yr8, AVS/6*Yr9, 'Clement' and 'Compair'. Race PST-80 is also virulent on 'Produra'. From 2003 to 2006, the predominant race was PST-100, with the same virulence formula as PST-80 plus virulence on 'Yamhill' and 'Stephens'. Starting in 2006, races with the same virulence formula of PST-100 plus virulence to Yr1 became predominant in California and races with the virulence of PST-100 plus virulence on Yr10 became predominant in the Pacific Northwest. During 2000 to 2007, races with more virulence factors became more predominant in the United States, indicating that races with increased virulence factors are at an advantage in the pathogen population over those with fewer virulence factors because they are able to infect more wheat cultivars. [ABSTRACT FROM AUTHOR]