Triticeae Genomics and Genetics, 2024, Vol.15, No.5, 244-254 http://cropscipublisher.com/index.php/tgg 245 This study provides a comprehensive overview of the genetic mechanisms and agronomic impacts of polyploidy in the Triticeae tribe. By exploring the evolutionary processes that have shaped the genomes of polyploid Triticeae species, with a focus on wheat and barley, it discusses the effects of polyploidy on the agronomic traits of these crops and the potential for future crop improvement. Polyploidy has played a key role in the evolution and domestication of Triticeae crops. Its role in generating genetic diversity and enhancing agronomic traits highlights the importance of continued research in this field. By synthesizing current research findings, the study examines the genetic complexity and practical significance of polyploidy, aiming to deepen the understanding of polyploidy in Triticeae and its importance for agriculture and plant breeding, offering valuable insights for researchers and breeders. 2 Mechanisms of Polyploidy Formation inTriticeae 2.1 Types of polyploidy: autopolyploidy and allopolyploidy Polyploidy, the condition of having more than two complete sets of chromosomes, is a significant evolutionary mechanism in plants, including the Triticeae tribe. There are two primary types of polyploidy: autopolyploidy and allopolyploidy. Autopolyploidy arises from the duplication of a single species' genome, leading to multiple sets of homologous chromosomes. This type of polyploidy can result in increased genetic material, which may provide a fitness advantage under certain environmental conditions (Svačina et al., 2020; Luque et al., 2022). On the other hand, allopolyploidy results from hybridization between two distinct species followed by chromosome doubling. This process combines divergent genomes, which can lead to novel genetic combinations and potentially new species (Huang and Zhu, 2018; Svačina et al., 2020). The formation of autopolyploids and allopolyploids involves different genetic and cytological mechanisms. Autopolyploids often face challenges such as multivalent formation during meiosis, which can lead to aneuploid gametes and reduced fertility (Svačina et al., 2020). In contrast, allopolyploids must establish compatibility between the divergent genomes and their regulatory networks, which can result in rapid genomic and phenotypic changes (Chen, 2007; Blasio et al., 2022). Despite these challenges, both types of polyploidy have been crucial in the evolution and diversification of the Triticeae tribe, contributing to their adaptability and speciation. 2.2 Molecular mechanisms of genome duplication The molecular mechanisms underlying genome duplication in polyploids involve a complex interplay of genetic and epigenetic factors. In autopolyploids, genome duplication typically occurs through errors in meiosis or mitosis, leading to the formation of unreduced gametes. These errors can be due to altered spindle organization, disturbed kinetochore function, or abnormal cytokinesis (Blasio et al., 2022). In allopolyploids, hybridization between different species is followed by chromosome doubling, which can be facilitated by similar meiotic errors or by somatic cell fusion (Mason and Wendel, 2020; Blasio et al., 2022). Once genome duplication occurs, polyploids undergo significant genomic and transcriptomic changes. These changes include alterations in DNA sequence, chromatin modifications, and RNA-mediated pathways, which can affect gene expression and phenotypic variation (Chen, 2007). Homoeologous recombination, where related chromosomes from different subgenomes pair and exchange genetic material, is a common feature in newly formed allopolyploids. This process can lead to genomic instability but also provides opportunities for evolutionary novelty and adaptation (Mason and Wendel, 2020). The stabilization of polyploid genomes involves the suppression of homoeologous recombination and the establishment of new regulatory networks, which are critical for the successful establishment and persistence of polyploid species (Mason and Wendel, 2020; Blasio et al., 2022). 2.3 Timeline of polyploidy events inTriticeae evolution The evolutionary history of the Triticeae tribe is marked by multiple polyploidy events, which have played a crucial role in their diversification and adaptation. Polyploidy events in Triticeae can be traced back to ancient whole-genome duplications, which have been followed by more recent polyploidization events. These events have contributed to the complex genomic architecture observed in modern Triticeae species (Figure 1) (Huang and Zhu, 2018; Peer et al., 2020). For instance, wheat (Triticum spp.) is a well-known allopolyploid that has undergone
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