Person: Wanyera, R.
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Wanyera
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Wanyera, R.
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- Distribution of Puccinia striiformis f. sp. tritici races and virulence in wheat growing regions of Kenya from 1970 to 2014(American Phytopathological Society, 2022) Wamalwa, M.; Wanyera, R.; Rodriguez-Algaba, J.; Boyd, L.; Owuoche, J.O.; Ogendo, j.; Bhavani, S.; Uauy, C.; Justesen, A.F.; Hovmoller, M.S.
Publication - Genetic and molecular dissection of stem rust (Ug99) resistance in bread wheat(CIMMYT, 2019) Randhawa, M.S.; Bhavani, S.; Huerta-Espino, J.; Juliana, P.; Rouse, M.N.; Wanyera, R.; Singh, R.P.
Publication - Erratum to: Association mapping of North American spring wheat breeding germplasm reveals loci conferring resistance to Ug99 and other African stem rust races(BioMed Central, 2016) Bajgain, P.; Rouse, M.N.; Bulli, P.; Bhavani, S.; Gordon, T.; Wanyera, R.; Njau, P.N.; Wolde, L.; Anderson, J.; Pumphrey, M.
Publication - Vulnerability of barley to African pathotypes of Puccinia graminis f. sp. tritici and sources of resistance(American Phytopathological Society (APS), 2017) Steffenson, B.; Case, A.J.; Pretorius, Z.; Coetzee, Vicky; Kloppers, F. J.; Zhou, H.; Chai, Yuan; Wanyera, R.; Macharia, G.; Bhavani, S.; Grando, S.The emergence of widely virulent pathotypes (e.g., TTKSK in the Ug99 race group) of the stem rust pathogen (Puccinia graminis f. sp. tritici) in Africa threatens wheat production on a global scale. Although intensive research efforts have been advanced to address this threat in wheat, few studies have been conducted on barley, even though pathotypes such as TTKSK are known to attack the crop. The main objectives of this study were to assess the vulnerability of barley to pathotype TTKSK and identify possible sources of resistance. From seedling evaluations of more than 1,924 diverse cultivated barley accessions to pathotype TTKSK, more than 95% (1,844) were found susceptible. A similar high frequency (910 of 934 = 97.4%) of susceptibility was found for the wild progenitor (Hordeum vulgare subsp. spontaneum) of cultivated barley. Additionally, 55 barley lines with characterized or putative introgressions from various wild Hordeum spp. were also tested against pathotype TTKSK but none was found resistant. In total, more than 96% of the 2,913 Hordeum accessions tested were susceptible as seedlings, indicating the extreme vulnerability of the crop to the African pathotypes of P. graminis f. sp. tritici. In total, 32 (1.7% of accessions evaluated) and 13 (1.4%) cultivated and wild barley accessions, respectively, exhibited consistently highly resistant to moderately resistant reactions across all experiments. Molecular assays were conducted on these resistant accessions to determine whether they carried rpg4/Rpg5, the only gene complex known to be highly effective against pathotype TTKSK in barley. Twelve of the 32 (37.5%) resistant cultivated accessions and 11 of the 13 (84.6%) resistant wild barley accessions tested positive for a functional Rpg5 gene, highlighting the narrow genetic base of resistance in Hordeum spp. Other resistant accessions lacking the rpg4/Rpg5 complex were discovered in the evaluated germplasm and may possess useful resistance genes. Combining rpg4/Rpg5 with resistance genes from these other sources should provide more durable resistance against the array of different virulence types in the Ug99 race group.
Publication - Genome-wide association study for multiple biotic stress resistance in synthetic hexaploid wheat(MDPI, 2019) Bhatta, M.R.; Morgounov, A.; Belamkar, V.; Wegulo, S.N.; Dababat, A.A.; Erginbas Orakci, G.; Moustapha El Bouhssini; Gautam, P.; Poland, J.; Akci, N.; Demir, L.; Wanyera, R.; Baenziger, P.S.Genetic resistance against biotic stress is a major goal in many wheat breeding programs. However, modern wheat cultivars have a limited genetic variation for disease and pest resistance and there is always a possibility of the evolution of new diseases and pests to overcome previously identified resistance genes. A total of 125 synthetic hexaploid wheats (SHWs; 2n = 6x = 42, AABBDD, Triticum aestivum L.) were characterized for resistance to fungal pathogens that cause wheat rusts (leaf; Puccinia triticina, stem; P. graminis f.sp. tritici, and stripe; P. striiformis f.sp. tritici) and crown rot (Fusarium spp.); cereal cyst nematode (Heterodera spp.); and Hessian fly (Mayetiola destructor). A wide range of genetic variation was observed among SHWs for multiple (two to five) biotic stresses and 17 SHWs that were resistant to more than two stresses. The genomic regions and potential candidate genes conferring resistance to these biotic stresses were identified from a genome-wide association study (GWAS). This GWAS study identified 124 significant marker-trait associations (MTAs) for multiple biotic stresses and 33 of these were found within genes. Furthermore, 16 of the 33 MTAs present within genes had annotations suggesting their potential role in disease resistance. These results will be valuable for pyramiding novel genes/genomic regions conferring resistance to multiple biotic stresses from SHWs into elite bread wheat cultivars and providing further insights on a wide range of stress resistance in wheat.
Publication - Global stem rust phenotyping network for wheat improvement(CIMMYT, 2018) Bhavani, S.; Wanyera, R.; Randhawa, M.S.; Macharia, I.; Singh, R.P.; Badebo, A.; Girma, B.
Publication - Sources of stem rust resistance in wheat-alien introgression lines(American Phytopathological Society (APS), 2016) Rahmatov, M.; Rouse, M.N.; Steffenson, B.; Andersson, S.C.; Wanyera, R.; Pretorius, Z.; Houben, A.; Kumarse, N.; Bhavani, S.; Johansson, E.Stem rust is one of the most devastating diseases of wheat. Widely virulent races of the pathogen in the Ug99 lineage (e.g., TTKSK) are threatening wheat production worldwide; therefore, there is an urgent need to enhance the diversity of resistance genes in the crop. The objectives of this study were to identify new sources of resistance in wheat-alien introgression derivatives from Secale cereale, Leymus mollis, L. racemosus, and Thinopyrum junceiforme, postulate genes conferring the resistance, and verify the postulated genes by use of molecular markers. From seedling tests conducted in the greenhouse, the presence of seven known stem rust resistance genes (Sr7b, Sr8a, Sr9d, Sr10, Sr31, Sr36, and SrSatu) was postulated in the wheat-alien introgression lines. More lines possessed a high level of resistance in the field compared with the number of lines that were resistant at the seedling stage. Three 2R (2D) wheat-rye substitution lines (SLU210, SLU238, and SLU239) seemed likely to possess new genes for resistance to stem rust based on their resistance pattern to 13 different stem rust races but the genes responsible could not be identified. Wheat-rye, wheat-L. racemosus, and wheat-L. mollis substitutions or translocations with single and multiple interchanges of chromosomes, in particular of the B and D chromosomes of wheat, were verified by a combination of genomic in situ hybridization and molecular markers. Thus, the present study identified novel resistance genes originating from different alien introgressions into the wheat genome of the evaluated lines. Such genes may prove useful in enhancing the diversity of stem rust resistance in wheat against widely virulent pathogen races such as those in the Ug99 lineage.
Publication - Genetic loci conditioning adult plant resistance to the Ug99 Race group and seedling resistance to races TRTTF and TTTTF of the stem rust pathogen in wheat landrace CItr 15026(American Phytopathological Society (APS), 2017) Babiker, E.M.; Gordon, T.; Bonman, J.M.; Shiaoman Chao; Rouse, M.N.; Yue Jin; Newcomb, M.; Wanyera, R.; Bhavani, S.Wheat landrace CItr 15026 previously showed adult plant resistance (APR) to the Ug99 stem rust race group in Kenya and seedling resistance to Puccinia graminis f. sp. tritici races QFCSC, TTTTF, and TRTTF. CItr 15026 was crossed to susceptible accessions LMPG-6 and Red Bobs, and 180 double haploid (DH) lines and 140 recombinant inbred lines (RIL), respectively, were developed. The 90K wheat iSelect single-nucleotide polymorphism platform was used to genotype the parents and populations. Parents and 180 DH lines were evaluated in the field in Kenya for three seasons. A major quantitative trait locus (QTL) for APR was consistently detected on chromosome arm 6AS. This QTL was further detected in the RIL population screened in Kenya for one season. Parents, F1, and the two populations were tested as seedlings against races TRTTF and TTTTF. In addition, the DH population was tested against race QFCSC. Goodness-of-fit tests indicated that the TRTTF resistance in CItr 15026 was controlled by two complementary genes whereas the TTTTF and QFCSC resistance was conditioned by one dominant gene. The TRTTF resistance loci mapped to chromosome arms 6AS and 6DS, whereas the TTTTF and QFCSC resistance locus mapped to the same region on 6DS as the TRTTF resistance. The APR identified in CItr 15026 should be useful in developing cultivars with durable stem rust resistance.
Publication - Decade of stem rust research on Ug99: progress and challenges(CIMMYT, 2016) Bhavani, S.; Njau, P.N.; Wanyera, R.; Girma, B.; Abeyo Bekele Geleta; Badebo, A.; Woldeab, G.; Singh, R.P.; Huerta-Espino, J.; Gordon, C.
Publication - Detection of wheat stem rust races TTHSK and PTKTK in the Ug99 race group in Kenya in 2014(American Phytopathological Society (APS), 2016) Fetch, T.; Zegeye, T.; Park, R.F.; Hodson, D.P.; Wanyera, R.Wheat stem rust, caused by Puccinia graminis f. sp. tritici, causes severe losses in wheat production under epidemic conditions. The detection of isolate Ug99 in east Africa (Pretorius et al. 2000) has raised global concerns of the vulnerability of wheat to stem rust. Since initial detection, 10 variants of Ug99 have been reported across 13 countries (Patpour et al. 2015). Wheat stem rust infection was widespread in Kenya in 2014. Fifty-two samples from common wheat were collected from the Mount Kenya and North, South, and Central Rift regions and analyzed for race identity in a level-3 biocontainment laboratory in Canada. Of these samples, 41 yielded viable spores for race pathotyping. Each sample was inoculated on 8-day-old seedlings of 20 single-gene differential lines using an inoculator, incubated for 16 h in a dew chamber in the dark, and subsequently moved to a growth cabinet set at 18 ± 1°C and 16-h photoperiod. Infected plants were rated 14 days postinoculation using a 0 to 4 infection type scale. Virulence analysis using the letter-code nomenclature system (Jin et al. 2008) identified two new races in the Ug99 race group from repeated experiments. Race TTHSK was identified from samples collected at Ngorengore (South Rift) and Njoro (field 13), which differs from the original Ug99 isolate (race TTKSK) by avirulence on gene Sr30. Race TTHSK is similar to race TTHST, which was detected previously by Newcomb et al. (manuscript in preparation). Race PTKTK was identified from samples collected at Rotian and Eor-Enkitok in the South Rift region, Cheplasgei and Kaplogoi in the North Rift region, and at the technology farm in Njoro in the Central Rift region. Race PTKTK differs from race PTKSK (first identified in 2007) by additional virulence to gene SrTmp, or alternatively differs from race TTKTK by avirulence to gene Sr21. Races TTKTK and TTKTT in the Ug99 race group with virulence to gene SrTmp were also found in 2014 (Patpour et al. 2015; Patpour et al. 2016). Virulence to SrTmp was detected soon after the deployment of the variety ‘Kenya Robin’ (which has SrTmp) in 2011. This report now brings the total number of variants in the Ug99 race group to 13 and highlights the importance of stem rust surveillance and race pathotyping, particularly in Kenya and surrounding countries in eastern Africa where evolution of new stem rust virulence is frequent.
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