Posts Tagged ‘Triticum aestivum’

Population- and genome-specific patterns of linkage disequilibrium and SNP variation in spring and winter wheat (Triticum aestivum L.)

Posted by Carelia Juarez on , in Journal Articles

Published in BMC Genomics  11: 727, 2010

Population- and genome-specific patterns of linkage disequilibrium and SNP variation in spring and winter wheat (Triticum aestivum L.)

 Shiaoman Chao, Jorge Dubcovsky, Jan Dvorak, Ming-Cheng Luo, Stephen P. Baenziger, Rustam Matnyazov, Dale R. Clark, Luther E. Talbert, James A. Anderson, Susanne Dreisigacker, Karl Glover, Jianli Chen, Kim Campbell, Phil L. Bruckner, Jackie C. Rudd, Scott Haley, Brett F. Carver, Sid Perry, Mark E. Sorrells and Eduard D. Akhunov

Background: Single nucleotide polymorphisms (SNPs) are ideally suited for the construction of high-resolution genetic maps, studying population evolutionary history and performing genome-wide association mapping experiments. Here, we used a genome-wide set of 1536 SNPs to study linkage disequilibrium (LD) and population structure in a panel of 478 spring and winter wheat cultivars (Triticum aestivum) from 17 populations across the United States and Mexico.

Results: Most of the wheat oligo pool assay (OPA) SNPs that were polymorphic within the complete set of 478 cultivars were also polymorphic in all subpopulations. Higher levels of genetic differentiation were observed among wheat lines within populations than among populations. A total of nine genetically distinct clusters were identified, suggesting that some of the pre-defined populations shared significant proportion of genetic ancestry. Estimates of population structure (FST) at individual loci showed a high level of heterogeneity across the genome. In addition, seven genomic regions with elevated FST were detected between the spring and winter wheat populations. Some of these regions overlapped with previously mapped flowering time QTL. Across all populations, the highest extent of significant LD was observed in the wheat D-genome, followed by lower LD in the A- and B-genomes. The differences in the extent of LD among populations and genomes were mostly driven by differences in long-range LD ( > 10 cM).

Conclusions: Genome- and population-specific patterns of genetic differentiation and LD were discovered in the populations of wheat cultivars from different geographic regions. Our study demonstrated that the estimates of population structure between spring and winter wheat lines can identify genomic regions harboring candidate genes involved in the regulation of growth habit. Variation in LD suggests that breeding and selection had a different impact on each wheat genome both within and among populations. The higher extent of LD in the wheat D-genome versus the A- and B-genomes likely reflects the episodes of recent introgression and population bottleneck accompanying the origin of hexaploid wheat. The assessment of LD and population structure in this assembled panel of diverse lines provides critical information for the development of genetic resources for genome-wide association mapping of agronomically important traits in wheat.

Implication of rate and time of nitrogen application on wheat (Triticum aestivum. l .) yield and quality in Kenya

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Animal & Plant Sciences 9(2): 1141-1146, 2011

Implication of rate and time of nitrogen application on wheat (Triticum aestivum. l .) yield and quality in Kenya

 P.A. Ooro, J.N. Malinga, D.G. Tanner and T.S. Payne

 In Kenya, Nitrogen is the first limiting macro-element on many farms where bread wheat (Triticum aestivum) has been grown continuously for more than a decade. On-farm trials were conducted in Kenya by superimposing the treatments on farmers’ fields in Nakuru (5 sites), Uasin Gishu (3 sites), and Timau (2 sites) districts during the main growing seasons of 1997-99. This was to study the effect of rate and time of application of fertilizer nitrogen (N) on bread wheat ( Triticum aestivum) grain yield, yield components, and grain quality. Wheat grain samples from the ten (N) nitrogen rates and timing treatments combined across replications were analysed at the Small Grain Institute, Bethlehem, Republic of South Africa for milling and baking quality in accordance with standard analytical procedures (Pyler, 1973; Kent, 1983; Hoseney, 1986). Results revealed that flour protein content (FPC) and grain nitrogen (GN) increased significantly in response to N rate. Nitrogen application increased timing of sedimentation (SDSS) rate and loaf volume, but decreased the kernel weight, falling number (FLN) and flour yield (FLY) percentage. N application had P<0.05 effects only on mixing development time (MDT), FLN and (SDSS). Split application of N resulted in superior quality attributes than when the entire N was applied at once. The sensitivity of rate and time of N application was found to be greater in the wheat quality attributes than the grain yield and yield components. These results can therefore be used insituations where good wheat prices are determined on the basis of grain quality.

Dough rheology of wheat recombinant lines in relation to allelic variants of Glu-1 and Glu-3 loci

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Published in Cereal  Research Communications 39(3): 386-393, 2011

Dough rheology of wheat recombinant lines in relation to allelic variants of Glu-1 and Glu-3 loci

E. Martínez-Cruz, E. Espitia-Rangel, H. E. Villaseñor-Mir, J. D. Molina-Galán, I. Benítez-Riquelme, A. Santacruz-Varela, R. J. Peña-Bautista

The influence of allelic variants of HMW Gand LMWG on viscoelastic properties of dough was evaluated in parents and 98 recombinant lines derived from the crosses Rebeca F2000 × Verano S91 and Galvez M87 × Bacanora T88. Genotypes were grown at Roque, Guanajuato during the Spring-Summer of 2008. Studied traits were mixing time, mixing stability and over-mixing tolerance, general strength of the dough and tenacity/extensibility ratio. HMWG alleles 1, 2*, 17 + 18 and 5 + 10 favored the quality of the dough and variants 2 + 12 and 7 + 9 were associated with low levels of gluten strength. A 7 + 9 allele was associated with genotypes prone to form tenacious dough. Alleles Glu-A3c, Glu-A3e, Glu-B3g and Glu-B3h from the cross Rebeca F2000 × Verano S91 affected positively the quality of gluten, while allelic variants Glu-A3b, Glu-B3h and Glu-D3c in the cross Galvez M87 × Bacanora T88 were associated with higher quality standards and its counterparts Glu-A3c, Glu-B3j and Glu-D3b were associated to lower quality parameters. Results also shown interaction among loci, hence breeders need to be aware not only of the effect of individual alleles but also its interaction.

The Emergence of Ug99 Races of the Stem Rust Fungus is a Threat to World Wheat Production

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Published in  Annual Review of Phytopathology 49: 465-481, 2011

The Emergence of Ug99 Races of the Stem Rust Fungus is a Threat to World Wheat Production

Ravi P. Singh, David P. Hodson, Julio Huerta-Espino, Yue Jin, Sridhar Bhavani, Peter Njau, Sybil Herrera-Foessel, Pawan K. Singh, Sukhwinder Singh and Velu Govindan

Race Ug99 of the fungus Puccinia graminis tritici that causes stem or black rust disease on wheat was first detected in Uganda in 1998. Seven races belonging to the Ug99 lineage are now known and have spread to various wheat-growing countries in the eastern African highlands, as well as Zimbabwe, South Africa, Sudan, Yemen, and Iran. Because of the susceptibility of 90% of the wheat varieties grown worldwide, the Ug99 group of races was recognized as a major threat to wheat production and food security. Its spread, either wind-mediated or human-aided, to other countries in Africa, Asia, and beyond is evident. Screening in Kenya and Ethiopia has identified a low frequency of resistant wheat varieties and breeding materials. Identification and transfer of new sources of race-specific resistance from various wheat relatives is underway to enhance the diversity of resistance. Although new Ug99-resistant varieties that yield more than current popular varieties are being released and promoted, major efforts are required to displace current Ug99 susceptible varieties with varieties that have diverse race-specific or durable resistance and mitigate the Ug99 threat.

 

Global status of wheat leaf rust caused by Puccinia triticina

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Published in Euphytica 179(1): 143-160

Global status of wheat leaf rust caused by Puccinia triticina

J. Huerta-Espino, R. P. Singh, S. Germán, B. D. McCallum, R. F. Park, W. Q. Chen, S. C. Bhardwaj and H. Goyeau

Leaf rust caused by Puccinia triticina is the most common and widely distributed of the three wheat rusts. Losses from leaf rust are usually less damaging than those from stem rust and stripe rust, but leaf rust causes greater annual losses due to its more frequent and widespread occurrence. Yield losses from leaf rust are mostly due to reductions in kernel weight. Many laboratories worldwide conduct leaf rust surveys and virulence analyses. Most currently important races (pathotypes) have either evolved through mutations in existing populations or migrated from other, often unknown, areas. Several leaf rust resistance genes are cataloged, and high levels of slow rusting adult plant resistance are available in high yielding CIMMYT wheats. This paper summarizes the importance of leaf rust in the main wheat production areas as reflected by yield losses, the complexity of virulence variation in pathogen populations, the role cultivars with race-specific resistance play in pathogen evolution, and the control measures currently practiced in various regions of the world.

http://www.springerlink.com/content/p141qxvwm4q7u4r3/

Improving wheat stripe rust resistance in Central Asia and the Caucasus

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Published in Euphytica 179 (1); 197-207, 2011

Improving wheat stripe rust resistance in Central Asia and the Caucasus

Z. M. Ziyaev, R. C. Sharma, K. Nazari, A. I. Morgounov, A. A. Amanov, Z. F. Ziyadullaev, Z. I. Khalikulov and S. M. Alikulov

Wheat is the most important cereal in Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) and the Caucasus (Armenia, Azerbaijan and Georgia). Stripe rust, caused by Puccinia striiformis f. sp. tritici is considered the most important disease of wheat in Central Asia and the Caucasus (CAC). Although stripe rust has been present in the region for a long time, it has become a serious constraint to wheat production in the past 10 years. This is reflected by the occurrence of five epidemics of stripe rust in the CAC region since 1999, the most recent in 2010. Several wheat varieties occupying substantial areas are either susceptible to stripe rust or possess a low level of resistance. Information on the stripe rust pathogen in terms of prevalent races and epidemiology is not readily available. Furthermore, there is an insufficient understanding of effective stripe rust resistance genes in the region, and little is known about the resistance genes present in the commercial varieties and advanced breeding lines. The deployment of resistant varieties is further complicated by putative changes in virulence in the pathogen population in different parts of the CAC. Twenty four out of 49 improved wheat lines received through international nurseries or other exchange programs showed high levels of resistance to stripe rust to local pathogen populations in 2009. Fifteen of the 24 stripe rust resistant lines also possessed resistance to powdery mildew. It is anticipated that this germplasm will play an important role in developing stripe rust resistant wheat varieties either through direct adoption or using them as parents in breeding programs.

http://www.springerlink.com/content/3858251175855787/

Race non-specific resistance to rust diseases in CIMMYT spring wheats

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Published in Euphytica 179(1); 175-186, 2011

Race non-specific resistance to rust diseases in CIMMYT spring wheats

R. P. Singh;   J. Huerta-Espino;  S. Bhavani; S. A. Herrera-Foessel; D. Singh; P. K. Singh; G. Velu;  R. E. Mason; Y. Jin; P. Njau; J. Crossa

Rust diseases continue to cause significant losses to wheat production worldwide. Although the life of effective race-specific resistance genes can be prolonged by using gene combinations, an alternative approach is to deploy varieties that posses adult plant resistance (APR) based on combinations of minor, slow rusting genes. When present alone, APR genes do not confer adequate resistance especially under high disease pressure; however, combinations of 4–5 such genes usually result in “near-immunity” or a high level of resistance. Although high diversity for APR occurs for all three rusts in improved germplasm, relatively few genes are characterized in detail. Breeding for APR to leaf rust and stripe rust in CIMMYT spring wheats was initiated in the early 1970s by crossing slow rusting parents that lacked effective race-specific resistance genes to prevalent pathogen populations and selecting plants in segregating populations under high disease pressure in field nurseries. Consequently most of the wheat germplasm distributed worldwide now possesses near-immunity or adequate levels of resistance. Some semidwarf wheats such as Kingbird, Pavon 76, Kiritati and Parula show high levels of APR to stem rust race Ug99 and its derivatives based on the Sr2-complex, or a combination of Sr2 with other uncharacterized slow rusting genes. These parents are being utilized in our crossing program and a Mexico-Kenya shuttle breeding scheme is used for selecting resistance to Ug99. High frequencies of lines with near-immunity to moderate levels of resistance are now emerging from these activities. After further yield trials and quality assessments these lines will be distributed internationally through the CIMMYT nursery system.

http://www.springerlink.com/content/c0gm557225003551/

Delivering rust resistant wheat to farmers: a step towards increased food security

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Published in Euphytica 179(1): 187-196, 2011

Delivering rust resistant wheat to farmers: a step towards increased food security

 A. K. Joshi; M. Azab;  M. Mosaad;  M. Moselhy;  M. Osmanzai; S. Gelalcha; G. Bedada; M. R. Bhatta; A. Hakim; P. K. Malaker; M. E. Haque;  T. P. Tiwari;  A. Majid; M. R. Jalal Kamali;  Z. Bishaw; R. P. Singh;  T. Payne;  H. J. Braun

An important step towards reducing the vulnerability of wheat in Africa and Asia to the Ug99 race of the stem rust pathogen is the substitution of current susceptible varieties with superior resistant varieties. In the 2008–2009 cropping season both seed multiplication and dissemination of Ug99 resistant varieties were initiated in Afghanistan, Bangladesh, Egypt, Ethiopia, Iran, India, Nepal and Pakistan. Ug99 resistant varieties must occupy about 5% of the area sown to wheat in each country to ensure sufficient seed to displace current popular varieties. Because of the underdeveloped seed industry and small farm sizes in most of these countries, various strategies are being applied for rapid multiplication and dissemination of resistant varieties. Approaches being used include pre-release seed multiplication while candidate resistant lines are being tested in national evaluation trials and farmer participatory selection. Resistant varieties are already released in Afghanistan, Bangladesh, Egypt and Pakistan and more varieties are expected to be released in 2010 in these and other countries. Our results show that some new Ug99 resistant lines have yield superiority over dominant local varieties. Activities and progress in seed multiplication using existing and new Ug99 resistant varieties are discussed.

http://www.springerlink.com/content/t127776u3n338823/

Phenotypic correlations, G × E interactions and broad sense heritability analysis of grain and flour quality characteristics in high latitude spring bread wheats from Kazakhstan and Siberia

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Published in Euphytica 171(1): 23-38, 2010

Phenotypic correlations, G × E interactions and broad sense heritability analysis of grain and flour quality characteristics in high latitude spring bread wheats from Kazakhstan and Siberia

Hugo Ferney Gómez-Becerra, Aigul Abugalieva, Alexei Morgounov, K. Abdullayev, L. Bekenova, M. Yessimbekova, G. Sereda, S. Shpigun, V. Tsygankov, Yu Zelenskiy, Roberto Javier Peña and Ismail Cakmak

Grain and flour samples of 42 high latitude spring bread wheat genotypes from Kazakhstan and Siberia evaluated in a multi-location trial were analyzed for grain concentrations of protein, zinc (Zn) and iron (Fe), as well as flour quality characteristics. The genotypes showed high grain protein concentrations (14–19%), but low dough strength was a common feature for most of them. Significant positive correlations were found between grain protein and flour protein, gluten, gliadin, gli/glu ratio, Zn, and Fe contents. Grain protein was also correlated positively with hardness, sedimentation, farinograph dough development time (DDT), stability time and ash content. Grain Fe concentration was positively associated with sedimentation, stability time, water absorption and valorimeter value, suggesting that improvements in micronutrient concentrations in the grain parallels enhancement in gluten strength. Interestingly, glutenin content correlated negatively with the concentrations of grain and flour protein, gluten, and minerals; and also with gluten deformation index (IDK), DDT, and stability time. Conversely, gliadin content showed strong positive correlations with the concentrations of grain and flour protein, gluten, and minerals. Gliadin also correlated positively, but in lesser magnitude, with DDT, stability time and IDK. Environment and G×E interaction were important sources of variation for some quality characteristics. This was reflected in the low broad sense heritability (H) values for traits related to flour strength, such as sedimentation, IDK, stability time and gliadin content. Breeding strategies, including three testing locations at the advanced selection stages, are adequate for the enhancement of most of the quality traits, but faster improvement in flour strength could be achieved with a larger number of locations.

Identifying high yielding stable winter wheat genotypes for irrigated environments in Central and West Asia

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Published in Euphytica 171(1): 53-64, 2010

Identifying high yielding stable winter wheat genotypes for irrigated environments in Central and West Asia

Ram C. Sharma, Alexei I. Morgounov, Hans J. Braun, Beyhan Akin, Mesut Keser, David Bedoshvili, Ahmet Bagci, Christopher Martius and Maarten van Ginkel

Improved winter wheat (Triticum aestivum L.) cultivars are needed for the diverse environments in Central and West Asia to improve rural livelihoods. This study was conducted to determine the performance of elite winter wheat breeding lines developed by the International Winter Wheat Improvement Program (IWWIP), to analyze their stability across diverse environments, and to identify superior genotypes that could be valuable for winter wheat improvement or varietal release. One hundred and one advanced winter wheat breeding lines and four check cultivars were tested over a 5-year period (2004–2008). Grain yield and agronomic traits were analyzed. Stability and genotypic superiority for grain yield were determined using genotype and genotype × environment (GGE) biplot analysis. The experimental genotypes showed high levels of grain yield in each year, with mean values ranging from 3.9 to 6.7 t ha−1. A set of 25 experimental genotypes was identified. These were either equal or superior to the best check based on their high mean yield and stability across environments as assessed by the GGE biplot analysis. The more stable high yielding genotypes were ID800994.W/Falke, Agri/Nac//Attila, ID800994W/Vee//F900K/3/Pony/Opata, AU//YT542/N10B/3/II8260/4/JI/Hys/5/Yunnat Esskiy/6/KS82W409/Spn and F130-L-1-12/MV12. The superior genotypes also had acceptable maturity, plant height and 1,000-kernel weight. Among the superior lines, Agri/Nac//Attila and Shark/F4105W2.1 have already been proposed for release in Kyrgyzstan and Georgia, respectively. The findings provide information on wide adaptation of the internationally important winter wheat genotypes, and demonstrate that the IWWIP program is enriching the germplasm base in the region with superior winter wheat genotypes to the benefit of national and international winter wheat improvement programs.