stem rust

Wheat stripe (Puccinia striiformis f. sp. tritici,=Pst) and stem (Puccinia graminis f. sp. tritici =Pgt) rusts are the most important wheat disease in Egypt as well as present in all wheat growing areas. This study to evaluate a set of tester lines of wheat carrying stripe Yr's, stem Sr's rust genes and selected Egyptian varieties have been studied for their response to Pst and Pgt at adult plant stage under field conditions in Sakha Agriculture Research Station, during the 2011 to 2014 growing seasons. The results revealed that stripe rust, it has been observed that the new race Yr27-virulence to Pst. In addition pathotypes were virulent for Yr2, Yr6, Yr7, Yr8, Yr9, Yr27, while Yr18 showed moderate susceptibility. On the other hand, Yr1, Yr5, Yr10, Yr15, Yr17, Yr32 and YrSP exhibited high levels of resistance. Regarding, evaluation of resistance genes sources of stem rust on ICARDA, CIMMYT wheat germplasm, and Egyptian wheat varieties released i.e. Misr1 and Misr2 which having Ug99_resistance genes Sr2 and Sr25 were found susceptible to Pgt, also Sr31 recorded infection moderately susceptible to susceptible at adult stage. Genes Sr2 complex, Sr24, Sr26, Sr27, and Sr32 were resistant at adult plant stages. The combination of Sr26 with Sr2 and Sr25 provided stem rust resistance in some CIMMYT wheat germplasm. The objectives of this work are: race analysis of wheat stem and stripe rust disease, evaluation the level and distribution of wheat stripe and stem rust in Egypt, and identification the resistance genes in commercial varieties or new promising lines using standard and molecular genetic markers. Egyptian germplasm such as Misr1, and Misr2 and others tester lines of wheat carrying stem rust Sr's were evaluative under field condition at adult stage in Egypt during 2014 growing season, Egyptian cultivars Misr1 and Misr2 were susceptible rated 10S-20S and Sr31 rated MSS. that results clearly presence a new Sr31-virulence. On other hand, genes Sr2 complex, Sr24, Sr26, Sr27 and Sr32 were resistant and combination of Sr26 with (Sr2 and Sr25) produced stem rust resistance in some CIMMYT wheat germplasm. Shahin et al., 2015, in APS Annual Meeting, Aug. 1-5, Pasadena, CA, US, (In Press).

Use of large-scale computational resources has permitted the first quantitative study of airborne migration routes of fungal spores between numerous key epidemiological hot-spots of wheat stem rust in Africa, the Middle East and the Indian subcontinent. By coupling a state-of-the-art Lagrangian particle dispersion model (NAME) with mechanistic epidemiological models, we simulate turbulent atmospheric transport of large ensembles of fungal spores from source sites. The models use highly resolved global meteorological datasets from the UK Meteorological Office. We consider release of P. graminis uredinospores from numerous source locations over an 11 year period (2003-2014) and simulate atmospheric trajectories over a 10 km2 spatial sampling grid to elucidate spore deposition rates at national, regional, and continental spatial scales. Our systematic exploration permits the first quantitative perspective and ranking of likely airborne transmission routes of wheat stem rust. We identify migration trends within and between the “Rift valley epidemiological zone”, the Middle East, the Indian Subcontinent, as well as South Africa. Our results indicate (I) consistent seasonal dispersal patterns, (II) likely airborne transmission of stem rust from the Middle East to North-East Africa, and (III) suggest that there is considerable risk of spread of Ug99 or other virulent races from Eastern Yemen to the Indian subcontinent. Model results indicate that over the 11 year study period, viable spore deposition occurred between Eastern Yemen and Pakistan on average 22 days per year during overlapping wheat growing seasons. The validity of the modelling framework has been successfully tested by comparison with survey data from the 2013 epidemic outbreak in Ethiopia, and was recently used as a risk assessment tool to provide rapid response advice in different East-African countries. Known stem rust race distributions are also supportive of the model outputs. The research we have been doing allows a quantitative perspective on likely airborne transmission routes of Ug99 or other virulent races of wheat rust. By that we hope to provide new insights and recommendations for future risk assessment, survey and control strategies and also to contribute to fundamental understanding of epidemiological spread on regional and continental scales. The work we would like to present is the result of a joint effort of Dr Laura Burgin and Dr Matt Hort from the UK Meteorological office, Dr Dave Hodson from CIMMYT, and Dr James Cox, Matthew Hitchings and me from the Epidemiology and Modelling group of Prof Gilligan in Cambridge.

Stem rust is a potentially destructive fungal disease of wheat worldwide. In 1998 Pgt pathotype TTKSK virulent to Sr31 was detected in Uganda. The same pathotype was confirmed in Lorestan and Hamedan provinces of Iran in 2007. We used a derivative of race TTKSK to phenotype 62 Iranian wheat landraces (resistant to stripe rust in a previous study) at the seedling stage to this new pathotype (TTSSK). Twenty eight accessions were evaluated for the presence of resistance genes Sr2, Sr22, Sr24, Sr25, Sr26, Sr35, Sr36 and Srweb using SSR markers. None carried Sr2, Sr24 or Sr26, but the presence of Sr22, Sr25, Sr35 and Sr36 was indicated. Some susceptible landraces predicted to carry Sr2 by marker analysis require further investigation. To evaluate defense gene expression in compatible and incompatible stem rust interactions we sampled resistant and susceptible cultivars at 0, 12, 18, 24, 72 hours post-inoculation (hpi). ?-1,3 glucanase expression was studied using qGLU-S and qGLUU-AS primers and a real-time PCR step-one ABI machine, with ?-tubulin and EF1-? genes used as internal controls. In incompatible interactions defense gene expression was increased at 24 hpi, but in compatible interactions the highest level of expression occurred at 12 hpi and was significantly decreased at 18 hpi. The results revealed that expression of defense genes such as ?-1,3 glucanase was earlier in compatible than in incompatible interactions but the expression level was less in incompatible interactions. On the other hand, in susceptible genotypes the expression of defense genes increased immediately after inoculation and declined sharply after infection. In contrast defense gene expression in resistant genotypes began to increase after establishment of the pathogen.