Person: Luster, D.G.
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Luster
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D.G.
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Luster, D.G.
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- Kenyan Isolates of Puccinia graminis f. sp. tritici from 2008 to 2014: virulence to SrTmp in the Ug99 race group and implications for breeding programs(American Phytopathological Society (APS), 2016) Newcomb, M.; Olivera Firpo, P.D.; Rouse, M.N.; Szabo, L.J.; Johnson, J.W.; Gale, S.; Luster, D.G.; Wanyera, R.; Macharia, G.; Bhavani, S.; Hodson, D.P.; Patpour, M.; Hovmoller, M.S.; Fetch, T.; Yue JinFrequent emergence of new variants in the Puccinia graminis f. sp. tritici Ug99 race group in Kenya has made pathogen survey a priority. We analyzed 140 isolates from 78 P. graminis f. sp. tritici samples collected in Kenya between 2008 and 2014 and identified six races, including three not detected prior to 2013. Genotypic analysis of 20 isolates from 2013 and 2014 collections showed that the new races TTHST, TTKTK, and TTKTT belong to the Ug99 race group. International advanced breeding lines were evaluated against an isolate of TTKTT (Sr31, Sr24, and SrTmp virulence) at the seedling stage. From 169 advanced lines from Kenya, 23% of lines with resistance to races TTKSK and TTKST were susceptible to TTKTT and, from two North American regional nurseries, 44 and 91% of resistant lines were susceptible. Three lines with combined resistance genes were developed to facilitate pathogen monitoring and race identification. These results indicate the increasing virulence and variability in the Kenyan P. graminis f. sp. tritici population and reveal vulnerabilities of elite germplasm to new races.
Publication - First Report of the Ug99 race group of Wheat Stem Rust, Puccinia graminis f. sp. tritici, in Egypt in 2014(American Phytopathological Society (APS), 2016) Patpour, M.; Hovmoller, M.S.; Shahin, A.; Newcomb, M.; Olivera Firpo, P.D.; Yue Jin; Luster, D.G.; Hodson, D.P.; Nazari, K.; Azab, M.Since the first detection of race TTKSK (Ug99) of Puccinia graminis f. sp. tritici in Uganda in 1998 (Pretorius et al. 2000), it has been a priority to track its further spread to other wheat growing areas. To date, 10 variants in the Ug99 race group have been detected in 12 countries, i.e., Uganda, Kenya, Ethiopia, Sudan, Tanzania, Eritrea, Rwanda, South Africa, Zimbabwe, Mozambique, Yemen and Iran (Patpour et al. 2015). In the 2014 crop season, the presence of virulence to Sr31 in Egypt was suspected based on preliminary field observations of high infection on sources of Sr31 planted as international stem rust trap nursery at 1) Sakha Agricultural Research Station in Kafrelsheikh (31.094059° N, 30.933899° E), 2) Al-Sharqia (30.601400° N, 31.510383° E), and 3) Nubaria (30.91464° N, 29.95543° E). At Sakha, wheat cv. PBW343 (carrying Sr31) was scored 30MS-S, and the monogenic line Benno Sr31/6*LMPG was scored 20MS-S at Al-Sharqia. Three samples from each of these lines were sent to the Global Rust Reference Center (GRRC, Denmark). At Nubaria, stem rust was observed on wheat cvs. Misr-1, Misr-2, Giza 168 and Giza 171, and infected samples were collected and sent under permit to the Foreign Disease-Weed Science Research Unit (MD, USA). Urediniospores of each sample were recovered on susceptible wheat cv. Morocco and McNair 701. Twenty-three and 11 single pustule isolates were derived and analyzed at GRRC and USDA-ARS Cereals Disease Laboratory, respectively, using 20 North American stem rust differential lines following standard race-typing procedure and infection type (IT) criteria determining virulence and avirulence (Jin et al. 2008). In addition, three supplemental tester lines of Siouxland (carrying Sr24+Sr31), Sisson (carrying Sr31+Sr36), and Triumph 64 (donor of SrTmp) were included to confirm virulence/avirulence to Sr24, Sr31, Sr36, and SrTmp. The experiments were repeated two to three times. Three races in the Ug99 race group were detected; TTKST (four isolates, IT 3+4 for Sr24, Sr31 and cv. Siouxland) from Al-Sharqia, TTKTK (13 isolates, IT 4 for Sr31, SrTmp and cv. Triumph 64) from Sakha, and TTKSK (2 isolates, IT 4 for Sr31) from Nubaria. This is the first confirmation of races in the Ug99 race group in Egypt, thereby extending the geographical distribution of Ug99-related races. Since Egypt may play a role as green-bridge for Puccinia graminis f. sp. tritici between East and North African countries and the wheat belts in the Middle East and Mediterranean region, the rust surveillance efforts should be intensified in affected countries as well as in neighboring regions.
Publication - Phenotypic and genotypic characterization of Race TKTTF of Puccinia graminis f. sp. tritici that caused a Wheat Stem Rust Epidemic in Southern Ethiopia in 2013–14(American Phytopathological Society (APS), 2015) Olivera Firpo, P.D.; Newcomb, M.; Szabo, L.J.; Rouse, M.N.; Johnson, J.W.; Gale, S.; Luster, D.G.; Hodson, D.P.; Cox, J.A.; Burgin, L.; Hort, M.C.; Gilligan, C.A.; Patpour, M.; Justesen, A.F.; Hovmoller, M.S.; Woldeab, G.; Hailu, E.; Kotu, B.H.; Tadesse, K.; Pumphrey, M.; Singh, R.P.; Yue JinA severe stem rust epidemic occurred in southern Ethiopia during November 2013 to January 2014, with yield losses close to 100% on the most widely grown wheat cultivar, ‘Digalu’. Sixty-four stem rust samples collected from the regions were analyzed. A meteorological model for airborne spore dispersal was used to identify which regions were most likely to have been infected from postulated sites of initial infection. Based on the analyses of 106 single-pustule isolates derived from these samples, four races of Puccinia graminis f. sp. tritici were identified: TKTTF, TTKSK, RRTTF, and JRCQC. Race TKTTF was found to be the primary cause of the epidemic in the southeastern zones of Bale and Arsi. Isolates of race TKTTF were first identified in samples collected in early October 2013 from West Arsi. It was the sole or predominant race in 31 samples collected from Bale and Arsi zones after the stem rust epidemic was established. Race TTKSK was recovered from 15 samples from Bale and Arsi zones at low frequencies. Genotyping indicated that isolates of race TKTTF belongs to a genetic lineage that is different from the Ug99 race group and is composed of two distinct genetic types. Results from evaluation of selected germplasm indicated that some cultivars and breeding lines resistant to the Ug99 race group are susceptible to race TKTTF. Appearance of race TKTTF and the ensuing epidemic underlines the continuing threats and challenges posed by stem rust not only in East Africa but also to wider-scale wheat production.
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