stem rust

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a significant disease limiting wheat yield in Ethiopia. Wheat varieties such as 'Digalu' with single major-effect stem rust resistance genes have not exhibited durable resistance in Ethiopia. Identifying wheat lines with adult plant resistance (APR) has been proposed as a strategy to select for durable resistance. Our objective was to test the hypothesis that APR to stem rust is non-race-specific. We selected 31 wheat lines (including 10 durum and 21 bread wheat lines) that were susceptible as seedlings to Pgt races TTKSK, TKTTF, and TRTTF. These 31 wheat lines and Digalu were evaluated in 2014 and 2015 at the Kulumsa Agricultural Research Center, Ethiopia. The lines were planted in 1 m rows and replicated twice in separate single-race-inoculated nurseries. The three single-race nurseries inoculated with Pgt races TTKSK, TKTTF, and TRTTF were separated by at least 100 m and included selective spreaders. Plot yield, thousand kernel weight (TKW), and visual disease responses were measured for each plot. We used a least-squared means test to detect differences in coefficient of infection and TKW of each line across paired race comparisons. Lines 'Park', 'CI11469', and 'CI12818' displayed significantly different coefficient of infections between races TTKSK and TRTTF. For CI11469 and CI12818, this difference was validated by significant differences in TKW. Significant differences in TKW were also detected between various race comparisons for 'ETHBW019', 'CI14798', 'CI15159', 'CI14618', and 'CI14094'. Our data demonstrated that APR in the selected germplasm was largely non-race-specific, but there were exceptions where race-specificity of APR was detected. These results have implications for resistance breeding and monitoring: testing of breeding material against prevalent Pgt races in target environments, not relying only on hotspot screening locations, and careful monitoring of deployed APR varieties are all warranted.

This work was carried out to study the response of five bread and two durum wheat cultivars to stem rust and its effect on grain yield under field conditions at Sids and Beni Sweif stations during the three growing seasons 2011/2012, 2012/2013 and 2013/2014. The loss in grain yield and kernel weight of the different wheat genotypes was variable according to the varietal response. Grain yield and kernel weight of the protected plots (protected by the effective fungicide Sumi-eight 5EC(CE)-1-(2,4-dichlorophenyl)1-4,4-dimethyl1-2-(1,2,4-triazol-y1)Pent -1-en -3-0L) at the rate of 70cm /200litter water per Fadden ) of all wheat genotypes were higher than the infected ones. Significant differences were found between infected and protected wheat genotypes.. Disease severity was recorded weekly to estimate area under disease progress curve (AUDPC). The AUDPC ranged from 85.33 to 405.00 (Sids 1 and Sohag 3) during 2011/2012, from 181.66 to 805.00 (Shandwel 1 and Sohag 3) during 2012/2013, and from 142.33 to 585.00 (Shandwel 1 and Sohag 3) during 2013/2014. Losses in kernel weight ranged from 3.39% to 31.03% (Sids 1 and Misr 1) during 2011/2012, from 9.79% to 44.18% (Sids 1 and Sohag 3) during 2012/2013,and from 5.67% to 26.86% (Sids 1 and Sohag 3) during 2013/2014. Yield losses ranged from 5.70% to 37.52% (Shandwel 1 and Misr 1) during 2011/2012, from 7.75% to 45.78% (Shandwel 1 and Misr 1) during 2012/2013, and from 7.14% to 30.59% (Sids 1 and Sohag 3) during 2013/2014. Yield losses correlated strongly with AUDPC. The results of this study indicate that bread wheat cultivars are (Giza 168,Sakha 93, Sids 1, Misr 1, Misr 2 and Shandwel 1) and Durum wheat are ( Beni Sweif 5 and Sohag 3) more tolerant than durum wheat cultivars. The Egyptian bread wheat cultivars Sids 1 and Shandawel 1 are more tolerant than the other bread wheat cultivars.
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An effective partnership between CIMMYT, KALRO, EIAR and Delivering Genetic Gains in Wheat (DGGW) project on global stem rust phenotyping has made a significant progress and impact on the Global wheat community in addressing the threat of Ug99 race group and other important stem rust races in the region. International stem rust phenotyping networks play a key role in evaluating global wheat germplasm from many countries and institutions: identifying new sources of resistance, pre-breeding, CIMMYT-Kenya shuttle breeding, pathogen survey and surveillance, varietal release and genomic selection. About 600,000 lines have been screened against Pgt race Ug99 and derivatives since 2005, and the screening capacity at KALRO has increased to 50,000 lines each year from over 20-25 countries and research institutions each year. The results from international nurseries show a shift to higher frequencies of lines with resistance to race Ug99 since the screening activities were initiated in 2008.
KALRO and EIAR and several national programs have a dynamic and successful breeding programs that benefit from collaboration, testing, and release of materials coming out of the CIMMYT breeding program. The release of over 15 varieties in Kenya as well as in Ethiopia and more than 90 varieties released in several countries globally over the years is a testament to the success of the program. with spillover effects of varieties released in Burundi, Rwanda, and Uganda.
CIMMYT-Kenya shuttle breeding has resulted in rapid recycling of over 2000 breeding populations each year between Mexico and Kenya to evaluate and select lines in early generations against virulent stem rust races in Kenya to ensure lines have adequate levels of resistance are advanced not only in early generations of breeding cycle but also materials in the yield trails (10,000 annually) that are later constituted as international nurseries and distributed to National programs and partners.

Rusts (Puccinia spp.) are the most significant disease affecting wheat yield and quality in Turkey. Knowing the resistance status of wheat genotypes in crossing program is an important issue for breeding programs. The aim of the study was to determine of the resistance of the 106 wheat genotypes consisting of Crossing Block Spring Wheat (CBSW) nursery developed by the International Winter Wheat Improved Project (IWWIP). For this purpose, adult plant and seedling test were conducted for yellow rust while only seedling test were conducted for leaf and stem rust. Evaluations were carried out at the research facilities of CRIFC at İkizce and Yenimahalle in Ankara in the 2014 season. For adult plant reactions; the genotypes were inoculated with local Pst populations (virulent on Yr2,6,7,8,9,25,27,Sd,Su,Avs). Stripe rust development on each entry were scored using the modified Cobb scale when the susceptible check Little Club had reached 80S infection severity in June, 2014. Coefficients of infections were calculated and values below 20 were considered to be resistant. For seedling test; the seedling was inoculated with local Pgt (avirulent on Sr24, Sr26, Sr27, and Sr31), Pt (avirulent on Lr9, Lr19, Lr24, and Lr28) and Pst populations. Stripe, leaf and stem rust development on each entry were scored after 14 days with 0-4 and 0-9 scale for leaf-stem rust and yellow rust, respectively. In seedling stage, thirty nine (37%), 47 (44%), and 20 (19%) genotypes were resistant to local Pgt, Pt, and Pst populations, respectively. In adult plant test, 46 (43%) genotypes were resistant to Pst.  The resistance genotypes to stem, leaf, and stripe rust were determined with this research.