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Yue Jin

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Yue Jin
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Yue Jin

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Author: Hovmoller, M.S. × AGROVOC: WHEAT ×

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    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.
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    Emergence of virulence to SrTmp in the Ug99 race group of wheat stem rust, Puccinia graminis f. sp. tritici, in Africa
    (American Phytopathological Society (APS), 2016) Patpour, M.; Hovmoller, M.S.; Justesen, A.F.; Newcomb, M.; Olivera Firpo, P.D.; Yue Jin; Szabo, L.J.; Shahin, A.; Wanyera, R.; Habarurema, I.; Wobibi, S.; Hodson, D.P.
    The Ug99 race (TTKSK) of wheat stem rust was first detected in Uganda in 1998 (Pretorius et al. 2000) and since then seven additional variants have been reported, i.e., TTKSF, TTKST, TTTSK, TTKSP, PTKSK, PTKST, and TTKSF+ (Pretorius et al. 2012). In this study, 84 stem rust samples from the 2014 surveys of wheat fields in Africa (Kenya, 9; Uganda, 28; Rwanda, 41; and Egypt, 6) were sent to the Global Rust Reference Center (GRRC, Denmark) for race analysis. Puccinia graminis f. sp. tritici (Pgt) samples were recovered on cv. Morocco, and resulting urediniospores of 53 single-pustule isolates were inoculated onto 20 North American stem rust differential lines using standard procedures (Jin et al. 2008). The pathotyping was repeated in two or three independent experiments. Twelve of the derived isolates were also typed at the USDA-ARS Cereal Disease Laboratory (USA) for an independent confirmation. Among the Kenyan samples, four collected from Njoro (Central Rift, cvs. Robin and Kwale) and two from Ntulumeti and Olgilai (South Rift, cv. Robin), were typed as TTKTK. Race TTKTK was similar to TTKSK except for additional virulence to SrTmp (Infection Type 4). An additional single-pustule isolate derived from one sample from Njoro showed a high infection type on LcSr24Ag and CnsSrTmp, testers for Sr24 and SrTmp, respectively, and was typed as TTKTT. These isolates were also tested on Siouxland (PI 483469, Sr24+Sr31), Sisson (PI 617053, Sr31+Sr36), and Triumph 64 (CI 13679, donor of SrTmp) to confirm their virulence/avirulence combinations to Sr24, Sr31, Sr36, and SrTmp. Race TTKTK was also detected at two locations in Uganda (Rubaya and Muko in Kabale region) and at five locations in Rwanda (Kinigi, Rwerere, Rufungo, Gatebe and Kamenyo). Three isolates derived from stem rust samples collected on cv. PBW343 (carrying Sr31) in Sakha in the Nile Delta region in Egypt were also typed as TTKTK. In addition, DNA from isolates of race TTKTK were analyzed using a diagnostic qPCR assay (Ug99 RG stage-1, Szabo unpublished data), which confirmed that these samples belong to the Ug99 lineage. The identification of SrTmp virulence in the Ug99 race group in several countries in one year emphasizes the relevance of coordinated international surveillance efforts and utilization of diverse sources of resistance to control stem rust in wheat. Further studies are in progress to determine the detailed relationship of the newly emerged races and other Pgt isolates identified in the Ug99 group.
    Publication
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    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 Jin
    A 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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    Emergence and spread of new races of wheat stem rust fungus: continued threat to food security and prospects of genetic control
    (American Phytopathological Society (APS), 2015) Singh, R.P.; Hodson, D.P.; Yue Jin; Lagudah, E.; Ayliffe, M.A.; Bhavani, S.; Rouse, M.N.; Pretorius, Z.; Szabo, L.J.; Huerta-Espino, J.; Basnet, B.R.; Lan, C.; Hovmoller, M.S.
    Race Ug99 (TTKSK) of Puccinia graminis f. sp. tritici, detected in Uganda in 1998, has been recognized as a serious threat to food security because it possesses combined virulence to a large number of resistance genes found in current widely grown wheat (Triticum aestivum) varieties and germplasm, leading to its potential for rapid spread and evolution. Since its initial detection, variants of the Ug99 lineage of stem rust have been discovered in Eastern and Southern African countries, Yemen, Iran, and Egypt. To date, eight races belonging to the Ug99 lineage are known. Increased pathogen monitoring activities have led to the identification of other races in Africa and Asia with additional virulence to commercially important resistance genes. This has led to localized but severe stem rust epidemics becoming common once again in East Africa due to the breakdown of race-specific resistance gene SrTmp, which was deployed recently in the ‘Digalu’ and ‘Robin’ varieties in Ethiopia and Kenya, respectively. Enhanced research in the last decade under the umbrella of the Borlaug Global Rust Initiative has identified various race-specific resistance genes that can be utilized, preferably in combinations, to develop resistant varieties. Research and development of improved wheat germplasm with complex adult plant resistance (APR) based on multiple slow-rusting genes has also progressed. Once only the Sr2 gene was known to confer slow rusting APR; now, four more genes—Sr55, Sr56, Sr57, and Sr58—have been characterized and additional quantitative trait loci identified. Cloning of some rust resistance genes opens new perspectives on rust control in the future through the development of multiple resistance gene cassettes. However, at present, disease-surveillance-based chemical control, large-scale deployment of new varieties with multiple race-specific genes or adequate levels of APR, and reducing the cultivation of susceptible varieties in rust hot-spot areas remains the best stem rust management strategy.
    Publication