Latest Research on Wheat Genetics: Feb 2021

Wheat Genetics Resource Center: The First 25 Years

The Wheat Genetics Resource Center, a pioneering center without walls, has served the wheat genetics community for 25 years. The Wheat Genetics Resource Center (WGRC) assembled a working collection of over 11,000 wild wheat relatives and cytogenetic stocks for conservation and use in wheat genome analysis and crop improvement. Over 30,000 samples from the WGRC collection of wheat wild relatives, cytogenetic stocks, and improved germplasm have been distributed to scientists in 45 countries and 39 states in the United States. The WGRC and collaborators have developed standard karyotypes of 26 species of the Triticum/Aegilops complex, rye, and some perennial genera of the Triticeae. They have developed over 800 cytogenetic stocks including addition, substitution, and deletion lines. The anchor karyotypes, technical innovations, and associated cytogenetic stocks are a part of the basic tool kit of every wheat geneticist. They have cytogenetically characterized over six‐dozen wheat–alien introgression lines. The WGRC has released 47 improved germplasm lines incorporating over 50 novel genes against pathogens and pests; some genes have been deployed in agriculture. The WGRC hosted over three‐dozen scientists especially from developing countries for advanced training. The WGRC was engaged in international agriculture through several collaborating projects. Particularly noteworthy was the collaborative project with Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) on the production of synthetic wheats. It is estimated that “by the year 2003–2004, 26% of all new advanced lines made available through CIMMYT screening nurseries to cooperators for either irrigated or semi‐arid conditions were synthetic derivatives.” The WGRC is applying genomics tools to further expedite the use of exotic germplasm in wheat crop improvement. [1]

Chromosome 1B-encoded gliadins and glutenin subunits in durum wheat: Genetics and relationship to gluten strength

The progenies of crosses between Berillo and four durum wheat cultivars were analysed for storage protein composition (by four different electrophoresis procedures), genetic segregation and gluten quality (by SDS sedimentation test and Viscoelastograph). The crosses enabled the segregation patterns of alleles at Gli-B1, Glu-B3 and Glu-B1 on chromosome 1B, and at Gli-A2 on chromosome 6A to be determined. The gene order on chromosome 1B was deduced to be Glu-B1-centromere-Glu-B3-Gli-B1, with 47% recombination between Glu-B1 and Glu-B3, and 2% between Glu-B3 and Gli-B1. Genes coding for γ-gliadins at Gli-B1 were distal to ω-gliadin genes with respect to the centromere. Analyses of the progeny (F4 grains) from single F2 plants, indicated that gliadins γ-42 and γ-45 are only genetic markers of quality, whereas allelic variation for low molecular weight (LMW) glutenin subunits encoded at the Glu-B3 locus is primarily responsible for differences in SDS sedimentation volume and gluten viscoelastic properties. High molecular weight (HMW) glutenin subunits 7+8 also gave larger SDS sedimentation volumes and higher gluten elastic recoveries than subunits 6+8 and 20. The positive effects of the so-called LMW-2 glutenin subunits and HMW subunits 7+8 were additive, with LMW-2 being the most important proteins for pasta-making quality as evaluated by SDS-sedimentation and gluten viscoelasticity (both parameters related to firmness of cooked pasta). Two alleles at Gli-A2 coding for α-gliadins were also found to have different effects on gluten firmness. [2]

Domestication evolution, genetics and genomics in wheat

Domestication of plants and animals is the major factor underlying human civilization and is a gigantic evolutionary experiment of adaptation and speciation, generating incipient species. Wheat is one of the most important grain crops in the world, and consists mainly of two types: the hexaploid bread wheat (Triticum aestivum) accounting for about 95% of world wheat production, and the tetraploid durum wheat (T. durum) accounting for the other 5%. In this review, we summarize and discuss research on wheat domestication, mainly focusing on recent findings in genetics and genomics studies. T. aestivum originated from a cross between domesticated emmer wheat T. dicoccum and the goat grass Aegilops tauschii, most probably in the south and west of the Caspian Sea about 9,000 years ago. Wild emmer wheat has the same genome formula as durum wheat and has contributed two genomes to bread wheat, and is central to wheat domestication. Domestication has genetically not only transformed the brittle rachis, tenacious glume and non-free threshability, but also modified yield and yield components in wheat. Wheat domestication involves a limited number of chromosome regions, or domestication syndrome factors, though many relevant quantitative trait loci have been detected. On completion of the genome sequencing of diploid wild wheat (T. urartu or Ae. tauschii), domestication syndrome factors and other relevant genes could be isolated, and effects of wheat domestication could be determined. The achievements of domestication genetics and robust research programs in Triticeae genomics are of greatly help in conservation and exploitation of wheat germplasm and genetic improvement of wheat cultivars. [3]

Genetic Components for Physiological Parameters Estimates in Bread Wheat (Triticum aestivum L.)

Aims: The specific objective of this study was to estimate the genetic components for some physiological parameters to use in breeding programs.
Place and Duration of Study: The present research was conducted in the Experiments Farm at University Putra Malaysia (UPM) during crop season 2010-2011.
Methodology: Eight bread wheat cultivars were used as parents and crosses for a half-diallel among these wheat cultivars were made in the Agriculture and Natural Resources Research Center of Sistan-Iran and genotypes were arranged as a Completely Randomised Block Design at research farms of university Putra Malysia.
Results: The combining ability analysis of variance showed that both general (GCA) and specific combining ability (SCA) variances were highly significant for all the characters except chlorophyll content for SCA, indicating the importance of both additive and non-additive gene effects. Chamran for relative water content and grain yield was the best combiner and the most narrow sense heritability belongs to stomatal conductance.
Conclusion: The eight wheat traits analyzed in this study were under dominance gene effects, Chamran with large, positive and significant GCA effects could be used as parent with desirable genes for genetic. [4]

Genetic Diversity and Molecular Characterization of Brazilian Wheat Varieties Obtained by Microsatellite Markers

Aims: Evaluating the genetic diversity and molecular characterization of wheat varieties in Brazil, using microsatellite markers.

Study Design: Random sampling of seeds from 32 varieties, was done.

Place and Duration of Study: Biotechnology lab, Coodetec, BR 467, km 98. Cascavel, PR, Brazil, between July 2011 to July 2012.

Methodology: Thirty-two varieties were evaluated with 23 markers, using capillary gel electrophoresis. After DNA extraction, and gels scoring, the genetic distances were obtained, the clustering by UPGMA method, the frequency of each allele and Probability of Random Identity (PRI).

Results: It was observed two to eight alleles by loci and genetic distances ranging from 0.31 to 0.90. The varieties were grouped into 11 groups. From the estimated PRI, 15 markers were identified that identify all 32 varieties with a maximum of 0.0001% PRI. High variability among wheat varieties was observed and also high efficiency in the identification of varieties with microsatellite markers.

Conclusion: This approach can be used in breeding programs and for the protection of intellectual property of wheat varieties breeders. [5]

Reference

[1] Gill, B.S., Friebe, B., Raupp, W.J., Wilson, D.L., Cox, T.S., Sears, R.G., Brown‐Guedira, G.L. and Fritz, A.K., 2006. Wheat genetics resource center: the first 25 years. Advances in Agronomy89, pp.73-136.

[2] Pogna, N.E., Autran, J.C., Mellini, F., Lafiandra, D. and Feillet, P., 1990. Chromosome 1B-encoded gliadins and glutenin subunits in durum wheat: genetics and relationship to gluten strength. Journal of Cereal Science11(1), pp.15-34.

[3] Peng, J.H., Sun, D. and Nevo, E., 2011. Domestication evolution, genetics and genomics in wheat. Molecular Breeding28(3), pp.281-301.

[4] Poodineh, M. and Rad, M.N., 2015. Genetic components for physiological parameters estimates in Bread wheat (Triticum aestivum L.). Annual Research & Review in Biology, pp.163-170.

[5] Luiz da Silva, A., Berwanger de Oliveira, M., Serra Negra Vieira, E., Sérgio Marchioro, V., de Assis Franco, F., & Schuster, I. (2015). Genetic Diversity and Molecular Characterization of Brazilian Wheat Varieties Obtained by Microsatellite Markers. Journal of Advances in Biology & Biotechnology4(3), 1-10. https://doi.org/10.9734/JABB/2015/18628.

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