Abstract
Allotetraploid durum wheat is the second most widely cultivated wheat, following hexaploid bread wheat, and is one of the major protein and calorie sources of the human diet. However, durum wheat is encountered with a severe grain yield bottleneck due to the erosion of genetic diversity stemming from long-term domestication and especially modern breeding programs. The improvement of yield and grain quality of durum wheat is crucial when confronted with the increasing global population, changing climate environments, and the non-ignorable increasing incidence of wheat-related disorders. This review summarized the domestication and evolution process and discussed the durum wheat re-evolution attempts performed by global researchers using diploid einkorn, tetraploid emmer wheat, hexaploid wheat (particularly the D-subgenome), etc. In addition, the re-evolution of durum wheat would be promoted by the genetic enrichment process, which could diversify allelic combinations through enhancing chromosome recombination (pentaploid hybridization or pairing of homologous chromosomes gene Ph mutant line induced homoeologous recombination) and environmental adaptability via alien introgressive genes (wide cross or distant hybridization followed by embryo rescue), and modifying target genes or traits by molecular approaches, such as CRISPR/Cas9 or RNA interference (RNAi). A brief discussion of the future perspectives for exploring germplasm for the modern improvement and re-evolution of durum wheat is included.
Highlights
Introduction published maps and institutional affilWheat is one of the main cereal crops in the world and a major source of carbohydrates and proteins in the human diet [1,2,3]
Tetraploid wheat is constituted by two groups: Timopheevi group wheat (Triticum timopheevi Zhuk., 2n = 4x = 28, Au Au Bsp Bsp /Au Au GG) and Turgidum group wheat (Triticum turgidum L., 2n = 4x = 28, Au Au BB) (Table 1), according to the Biosystematics of Triticeae updated by Yen and Yang [17]
The comparison of genome sequences of five Aegilops Sitopsis species showed that Ae. speltoides and the B-subgenome diverged about 4.49 million years before present (BP), which was much earlier than the speciation of tetraploid emmer wheat [45]
Summary
Tetraploid wheat is constituted by two groups: Timopheevi group wheat (Triticum timopheevi Zhuk., 2n = 4x = 28, Au Au Bsp Bsp /Au Au GG) and Turgidum group wheat (Triticum turgidum L., 2n = 4x = 28, Au Au BB) (Table 1), according to the Biosystematics of Triticeae updated by Yen and Yang [17]. The origin of allotetraploid wheat can be traced back to presumably 0.3–0.5 million years before present (BP) in or near the oak-pistachio woodland belt, called Near Eastern Fertile Crescent (Figure 1) [29,30,31]. Wild, hulled, brittle rachis domesticated, hulled, semi-brittle rachis cultivated, free-threshing, tough rachis cultivated, free-threshing, tough rachis cultivated, free-threshing, tough rachis cultivated, free-threshing, tough rachis. Au Au BB concv., cultivar-group; var., variety
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