Wheat stem rust epidemics caused by the obligate pathogenic fungus Puccinia graminis f.sp. tritici have historically driven severe yield losses on all wheat growing continents and, after many decades of control, stem rust is re-emerging as a disease of concern. In 1998, a highly virulent race able to overcome 90% of world wheat cultivars, Ug99, was identified in Uganda. Since initial detection, the pathogen has evolved many new variants and spread to many countries. The original variant spread from East Africa to the Middle East with three years between detection in Ethiopia and subsequent detection in Yemen. In 2014, another Ug99 variant (TTKTT), with one of the most complex virulence profiles, was detected in Kenya. This variant also spread from East Africa to the Middle East, but with only one year between detection in Ethiopia and subsequent detection in Iraq. Here we investigate potential airborne migration routes to account for the rapid spread of TTKTT in East Africa and beyond to the Middle East by using an integrated model combining the outputs from a meteorology-driven fungal spore dispersion model with epidemiological models to account for seasonal availability of susceptible crops and conditions for spore release and infectivity. We find viable pathways in the 2018/19 season that incorporate critical stepping-stone locations in Yemen or Saudi Arabia, but only in the presence of newly irrigated regions in Ethiopia. Our results indicate the potential and increasing importance of irrigated wheat areas in Ethiopia, Yemen and Saudi Arabia for inter-regional stem rust movements. Future movement of stem rust races out of East Africa is considered likely as irrigated areas expand. Targeted surveillance and the use of mitigation strategies including the use of durable resistant varieties in regions of irrigation are required to reduce the risks of enhanced dispersal of stem rust to other regions.
Wheat stem rust caused by Puccinia graminis f.sp tritici is constant biotic constraint of wheat production across the world. Because of quick alteration of genetic makeup of wheat stem rust pathogen; monitoring shift in virulence within pathogen is crucial to avoid sudden occurrence of epidemics due race change. This study was to identify physiological races stem rust pathogen in Ethiopia during 2019 cropping season. Wheat stem rust samples were collected during 2019 main cropping season from major wheat growing areas of Oromia, Amhara, Tigray and Southern Nations Nationalities and Peoples regions of Ethiopia. Besides, samples were also collected from Afar region where wheat was grown by irrigation during off season. The samples where isolated on universally wheat stem rust susceptible line (McNair) for the sake of mono pustule isolation and multiplication to have sufficient spores. Each isolates where inoculated on twenty standard differential lines and each line was evaluated after fourteen days to determine the races. Eight stem rust races namely, TKKTF, TKTTF, TTTTF, TKKTT, TTKTT, TTRTF, TKPTF and TTKTF were identified from samples analyzed; TKKTF was identified from 175 (44.1%) stem rust isolates, while TTTTF was detected from 73 (18.4) samples analyzed. In addition, TKTTF was isolated from 70 (17.8%) samples; however, TTKTF, TTKTT, TTRTF, TKPTF and TKKTT were recorded from 48 (12.1%), 21 (5.3%), 4 (1%), 1 (0.25%) and 1 (0.25%) samples analyzed in the season. TTKTT races have 95% virulence spectra to stem rust
In Ethiopia, stem rust caused by Puccinia graminis f. sp. tritici (Pgt) is one of the most serious wheat diseases. On vulnerable cultivars, it has the ability to cause yield losses of up to 100%. The infection responses of forty-two wheat lines at the seedling stage against eleven isolates of stem rust race TTKSK (Ug99 race), TTRTF, TKTTF (Digalu race), JRCQC, TKKTF, TRTTF, TTTTF, TTKTF, TTKTT, RRTTF, and TKPTF were evaluated in a study. Wheat lines were experimentally infected with urediniospores of the races under controlled conditions at Ambo Plant Protection Research Center in 2021. Against the Pgt races that were examined, different seedling resistance responses were seen. Thirteen wheat lines,
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