Triticeae Genomics and Genetics, 2024, Vol.15, No.3, 125-136 http://cropscipublisher.com/index.php/tgg 128 Figure 2 Genomic diversity and taxonomic tree of Triticae species (Adapted from Chen et al., 2020) Image caption: The A-tree structure indicates the common ancestor of all Triticae species, from which different species and genomes gradually differentiate, forming the diversity of modern Triticae species; B further refined this classification, displaying different types of genomes such as wild-type, cultivated type, and hybrid type (Adapted from Chen et al., 2020) 2.3 Challenges and controversies inTriticeae taxonomy Despite advances in wheat taxonomy, there are still some challenges and controversies. A major issue is that the descriptions of genera and species are incomplete and sometimes inconsistent. For example, evaluations of some genome classification systems have shown that many operational taxonomic units (OTUs) cannot be resolved due to the presence of homoplasticity and parallel homology, indicating the need for a more comprehensive approach to treat all attributes equally (Rodriguez-R et al., 2018) Another challenge is the morphological identification of genomic genera, particularly in perennial species with solitary spikelets. While it is possible to distinguish these groups based on morphology, it requires the examination of characters that have not been traditionally emphasized, such as the length of middle inflorescence internodes and the morphology of glumes (Barkworth et al., 2009). This highlights the ongoing need for detailed morphological studies to complement genomic data. Moreover, the integration of wild and weedy taxa into the taxonomic framework poses additional difficulties. These taxa are often underrepresented in genetic studies, and there is limited knowledge about their seed physiology, genetic diversity, and seed handling techniques (Bothmer et al., 2008). Addressing these gaps is essential for a more comprehensive understanding of Triticeae taxonomy and for the effective utilization of these genetic resources in crop improvement. In conclusion, the taxonomy of Triticeae is a complex and evolving field that requires the integration of morphological, cytogenetic, and genomic data. While significant progress has been made, ongoing research and refinement of classification systems are necessary to address the remaining challenges and controversies. 3 Wild Species of Triticeae 3.1 Overview of wildTriticeae species The tribe Triticeae encompasses approximately 350 wild taxa, which form a significant gene pool for temperate cereals such as wheat, barley, and Rye, as well as several important forage grasses(Bothmer et al., 2008). Despite the vast number of species, the primary focus has traditionally been on the primary gene pools of cultivated species, with wild and weedy taxa receiving less attention until recent years(Bothmer et al., 2008). The wild species, which include around 250 perennial species, are crucial for their genetic diversity and potential to improve cultivated varieties.
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