Wheat stripe rust (yellow rust [Yr]), caused by Puccinia striiformis f. sp. tritici, is an economically important disease of wheat worldwide. Virulence information on P. striiformis f. sp. tritici populations is important to implement effective disease control with resistant cultivars. In total, 235 P. striiformis f. sp. tritici isolates from Algeria, Australia, Canada, Chile, China, Hungary, Kenya, Nepal, Pakistan, Russia, Spain, Turkey, and Uzbekistan were tested on 20 single Yr-gene lines and the 20 wheat genotypes that are used to differentiate P. striiformis f. sp. tritici races in the United States. The 235 isolates were identified as 129 virulence patterns on the single-gene lines and 169 virulence patterns on the U.S. differentials. Virulences to YrA, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, YrUkn, Yr28, Yr31, YrExp2, Lemhi (Yr21), Paha (YrPa1, YrPa2, YrPa3), Druchamp (Yr3a, YrD, YrDru), Produra (YrPr1, YrPr2), Stephens (Yr3a, YrS, YrSte), Lee (Yr7, Yr22, Yr23), Fielder (Yr6, Yr20), Tyee (YrTye), Tres (YrTr1, YrTr2), Express (YrExp1, YrExp2), Clement (Yr9, YrCle), and Compair (Yr8, Yr19) were detected in all countries. At least 80% of the isolates were virulent on YrA, Yr2, Yr6, Yr7, Yr8, Yr17, YrUkn, Yr31, YrExp2, Yr21, Stephens (Yr3a, YrS, YrSte), Lee (Yr7, Yr22, Yr23), and Fielder (Yr6, Yr20). Virulences to Yr1, Yr9, Yr25, Yr27, Yr28, Heines VII (Yr2, YrHVII), Paha (YrPa1, YrPa2, YrPa3), Druchamp (Yr3a, YrD, YrDru), Produra (YrPr1, YrPr2), Yamhill (Yr2, Yr4a, YrYam), Tyee (YrTye), Tres (YrTr1, YrTr2), Hyak (Yr17, YrTye), Express (YrExp1, YrExp2), Clement (Yr9, YrCle), and Compair (Yr8, Yr19) were moderately frequent (>20 to <80%). Virulence to Yr10, Yr24, Yr32, YrSP, and Moro (Yr10, YrMor) was low (≤20%). Virulence to Moro was absent in Algeria, Australia, Canada, Kenya, Russia, Spain, Turkey, and China, but 5% of the Chinese isolates were virulent to Yr10. None of the isolates from Algeria, Canada, China, Kenya, Russia, and Spain was virulent to Yr24; none of the isolates from Algeria, Australia, Canada, Nepal, Russia, and Spain was virulent to Yr32; none of the isolates from Australia, Canada, Chile, Hungary, Kenya, Kenya, Nepal, Pakistan, Russia, and Spain was virulent to YrSP; and none of the isolates from any country was virulent to Yr5 and Yr15. Although the frequencies of virulence factors were different, most of the P. striiformis f. sp. tritici isolates from these countries shared common virulence factors. The virulences and their frequencies and distributions should be useful in breeding stripe-rust-resistant wheat cultivars and understanding the pathogen migration and evolution.
Disease incidence and severity was studied for winter wheat variety Bezostaya 1 and susceptible checks based on data from international nurseries from 1969 to 2010 and from 51 countries across major winter wheat production regions totalling 1,047 reports. The frequency of leaf rust and stripe rust occurrence was stable over time with marked increases in severity in 2001-2010 especially in Europe and Central and West Asia. Substantial global reductions in stem rust occurrence were recorded and attributed primarily to use of resistance genes although the recent emergence of race Ug99 makes wheat more vulnerable. The occurrence of powdery mildew remained globally stable over time. It was the most important foliar disease in Western and Southern Europe, where the frequency was very high for all time periods coupled with slight increases in severity during 2001-2010. The durable resistance of variety Bezostaya 1 to all four diseases was demonstrated in the study using comparisons of disease severities of Bezostaya 1 and the most susceptible entries. The Lr34/Yr18/Pm38 pleiotrophic set possessed by Bezostaya 1 is currently an important target for selection because it is now amenable to molecular selection. Increased use of genes like Lr34 combined with strategies to minimize Eur J Plant Pathol (2012) 132:323-340
Improved winter wheat (Triticum aestivum L.) cultivars are needed for the diverse environments in Central and West Asia to improve rural livelihoods. This study was conducted to determine the performance of elite winter wheat breeding lines developed by the International Winter Wheat Improvement Program (IWWIP), to analyze their stability across diverse environments, and to identify superior genotypes that could be valuable for winter wheat improvement or varietal release. One hundred and one advanced winter wheat breeding lines and four check cultivars were tested over a 5-year period (2004)(2005)(2006)(2007)(2008). Grain yield and agronomic traits were analyzed. Stability and genotypic superiority for grain yield were determined using genotype and genotype 9 environment (GGE) biplot analysis. The experimental genotypes showed high levels of grain yield in each year, with mean values ranging from 3.9 to 6.7 t ha -1 . A set of 25 experimental genotypes was identified. These were either equal or superior to the best check based on their high mean yield and stability across environments as assessed by the GGE biplot analysis. The more stable high yielding genotypes were ID800994.W/Falke, Agri/Nac//Attila, ID8009 94W/Vee//F900K/3/Pony/Opata, AU//YT542/N10B/ 3/II8260/4/JI/Hys/5/Yunnat Esskiy/6/KS82W409/Spn and F130-L-1-12/MV12. The superior genotypes also had acceptable maturity, plant height and 1,000-kernel weight. Among the superior lines, Agri/Nac//Attila and Shark/F4105W2.1 have already been proposed for release in Kyrgyzstan and Georgia, respectively. The findings provide information on wide adaptation of the internationally important winter wheat genotypes, and demonstrate that the IWWIP program is enriching the germplasm base in the region with superior winter wheat genotypes to the benefit of national and international winter wheat improvement programs.
Development of winter wheat (Triticum aestivum) synthetics started at CIMMYT-Mexico in 2004, when winter durum wheat (Triticum turgidum) germplasm from Ukraine and Romania was crossed with Aegilops tauschii accessions from the Caspian Sea region. Chromosomes were doubled after pollination and embryo rescue, but chromosome number and cytological validation was not performed. F2 populations were grown in Mexico and were shipped to Turkey in 2008. During 2009–2015, these populations were subjected to rigorous pedigree selection under dry, cold, disease-affected environments of the Central Anatolian Plateau. The wide segregation and partial sterility observed in 2009 gradually decreased and, by 2016, most of the F8 single spike progenies demonstrated good fertility and agronomic performance. Since 2013, lines have been selected from synthetic populations and evaluated at multiple sites. Superior lines were characterized for resistance to leaf, stripe and stem rust, plant height, and reaction to common bunt and soil-borne pathogens. Thousand kernel weight of many lines exceeded 50 g, compared with the check varieties that barely reached 40 g. Threshability of synthetic lines varied from 0 to 95%, demonstrating genetic variation for this important domestication trait. Screening against Hessian fly, sunny pest and Russian wheat aphid identified several resistant genotypes. Both durum and Aegilops parents affected synthetic wheat traits. Several studies are underway to reveal the genetic diversity of synthetic lines and the basis of resistance to diseases and insects. This synthetic germplasm represents a new winter bread wheat parental pool. It is available upon request to interested breeding/research programmes.
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