Domestication of Wheat
Another crop of the utmost importance, for the present and the future population, is wheat (Triticum spp.).
There are two main types of ancient domesticated wheat: the Einkorn (Triticum monococcum ssp. monococcum) and the Emmer (T. turgidum ssp. dicoccum L). They got replaced by a tetraploid free-threshing wheat (Durum Wheat) that evolved from the Emmer Wheat, that throuhout time give place to the common wheat (Triticum aestivum) we know today (Faris, 2014). There are 3 main genes involved in this crop domestication: Br (Brittle rachis), Q (free-threshing), and Tg (Tenacious glume) (Figure 1).
In natural conditions, the seed dispersal is crucial for the dissemination of the species, a characteristic defined by brittle rachis (Br), but, for human use is not an advantageous strategy, because it difficult the harvesting process. This phenotype is controlled by a gene present in the 2A or 3A and 3B (depending on the species) chromosome, so a mutation must have occurred there to give rise to a crop that doesn’t release the seeds, creating the non-brittle rachis Wheat we cultivate today (Peleg et al., 2011; Faris, 2014). An important characteristic in the post-harvesting processes is controlled by the Q allele (transcription factor of the AP2 family) present in the chromosome 5A long arm, that besides the free-threshing also pleiotropically affects other traits such as rachis fragility, the glume, and the plaint height (Simons et al., 2006; Peleg et al., 2011). The threshability is also controlled by the Tenacious glume(Tg) gene, that helps to maintain the seed attached to the spikelets (Peleg et al., 2011; Faris et al., 2014).
Peleg, Z., Fahima, T., Korol, A., Abbo, S. and Saranga, Y. (2011). Genetic analysis of wheat domestication and evolution under domestication. Journal of Experimental Botany, 62(14), pp.5051-5061.
Simons, K. J., Fellers, J. P., Trick, H. N., Zhang, Z., Tai, Y.-S., Gill, B. S., & Faris, J. D. (2006). Molecular Characterization of the Major Wheat Domestication Gene Q. Genetics, 172(1), 547–555.
There are two main types of ancient domesticated wheat: the Einkorn (Triticum monococcum ssp. monococcum) and the Emmer (T. turgidum ssp. dicoccum L). They got replaced by a tetraploid free-threshing wheat (Durum Wheat) that evolved from the Emmer Wheat, that throuhout time give place to the common wheat (Triticum aestivum) we know today (Faris, 2014). There are 3 main genes involved in this crop domestication: Br (Brittle rachis), Q (free-threshing), and Tg (Tenacious glume) (Figure 1).
In natural conditions, the seed dispersal is crucial for the dissemination of the species, a characteristic defined by brittle rachis (Br), but, for human use is not an advantageous strategy, because it difficult the harvesting process. This phenotype is controlled by a gene present in the 2A or 3A and 3B (depending on the species) chromosome, so a mutation must have occurred there to give rise to a crop that doesn’t release the seeds, creating the non-brittle rachis Wheat we cultivate today (Peleg et al., 2011; Faris, 2014). An important characteristic in the post-harvesting processes is controlled by the Q allele (transcription factor of the AP2 family) present in the chromosome 5A long arm, that besides the free-threshing also pleiotropically affects other traits such as rachis fragility, the glume, and the plaint height (Simons et al., 2006; Peleg et al., 2011). The threshability is also controlled by the Tenacious glume(Tg) gene, that helps to maintain the seed attached to the spikelets (Peleg et al., 2011; Faris et al., 2014).
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| Figure 1- Domestication evolution of Wheat (Faris, 2014). |
Bibliography
Faris, J. (2014). Wheat Domestication: Key to Agricultural Revolutions Past and Future. In: Tuberosa, R., Graner, A. and Frison, E. (n.d.). Genomics of plant genetic resources.Peleg, Z., Fahima, T., Korol, A., Abbo, S. and Saranga, Y. (2011). Genetic analysis of wheat domestication and evolution under domestication. Journal of Experimental Botany, 62(14), pp.5051-5061.
Simons, K. J., Fellers, J. P., Trick, H. N., Zhang, Z., Tai, Y.-S., Gill, B. S., & Faris, J. D. (2006). Molecular Characterization of the Major Wheat Domestication Gene Q. Genetics, 172(1), 547–555.
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