Triticeae Genomics and Genetics, 2024, Vol.15, No.3, 125-136 http://cropscipublisher.com/index.php/tgg 129 3.2 Ecological roles and natural habitats Wild Triticeae species occupy diverse ecological niches and play significant roles in their natural habitats. These species are found across various regions, often thriving in environments where cultivated species may not survive. For instance, many wild species are adapted to extreme conditions, contributing to the ecological stability and resilience of their habitats (Bothmer et al., 2008). The perennial species, which make up a substantial portion of the Triticeae tribe, are particularly important as forage grasses, supporting both natural ecosystems and agricultural systems. 3.3 Genetic diversity and evolutionary significance The genetic diversity within wild Triticeae species is immense and holds considerable evolutionary significance. This diversity is not only crucial for the adaptation and survival of these species in their natural habitats but also provides a valuable genetic reservoir for breeding programs aimed at improving cultivated cereals(Bothmer et al., 2008; Uauy, 2011). The structural polymorphisms observed in the chromosomes of wild species, such as those in the St, P, and Y genomes, highlight the evolutionary processes and genetic variability within the tribe (Wang et al., 2010). Understanding and utilizing this genetic diversity is essential for advancing our knowledge of Triticeae evolution and for the sustainable improvement of cereal crops (Uauy, 2011; Mochida and Shinozaki, 2013). 4 Cultivated Species of Triticeae 4.1 Major cultivated species The Triticeae tribe includes several major cultivated species that are of significant agricultural importance globally. The primary cultivated species are wheat (Triticum spp.), barley (Hordeum vulgare), and rye (Secale cereale) (Bothmer et al., 2008; Merker, 2008). Wheat is one of the most widely grown crops worldwide, providing a staple food source for a large portion of the global population. Barley is primarily used for animal feed, brewing, and as a food grain, while rye is cultivated mainly in cooler climates and is used for bread, beer, and animal fodder (Merker, 2008). 4.2 Domestication history and agronomic traits The domestication of these major Triticeae species has a rich history that dates back thousands of years. Wheat, for instance, was domesticated from wild emmer (Triticum dicoccoides) and other wild relatives in the Fertile Crescent around 10,000 years ago (Xie and Nevo, 2008). Barley was also domesticated in the same region and time period, while rye's domestication occurred later, primarily in Europe (Merker, 2008). Agronomic traits of these species have been extensively studied and improved through breeding programs. Key traits include disease resistance, drought tolerance, and grain quality. For example, wild emmer harbors genes for abiotic stress tolerances (e.g., salt, drought, and heat) and biotic stress tolerances (e.g., powdery mildew, rusts) that have been transferred to cultivated wheat to enhance its resilience and productivity (Xie and Nevo, 2008). Similarly, the genetic diversity within Triticum urartu has been explored to identify alleles that can improve wheat agronomy and quality (Talini et al., 2019). 4.3 Genetic diversity within cultivated species Genetic diversity within cultivated Triticeae species is crucial for their continued improvement and adaptation to changing environmental conditions. Wheat, barley, and rye have benefited from the genetic resources of their wild relatives, which provide a vast reservoir of alleles for various agronomic traits (Bothmer et al., 2008; Merker, 2008). For instance, the North American Triticale Genetic Resources Collection (NATGRC) has been established to conserve and evaluate the genetic diversity of triticale, a hybrid of wheat and rye, highlighting the importance of preserving unique gene combinations for future breeding efforts. The genetic diversity within these species is also evident in the various genotypic and phenotypic traits observed in different accessions. For example, a study on Triticum urartu reported significant variation in phenology, plant architecture, and seed features(Figure 3), demonstrating the potential of this wild wheat relative to contribute valuable alleles for wheat improvement (Talini et al., 2019). Similarly, the diversity indices and principal
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