Triticeae Genomics and Genetics, 2024, Vol.15, No.5, 244-254 http://cropscipublisher.com/index.php/tgg 247 hybrid breeding between common wheat and related wild species has led to significant chromosomal changes, such as the well-known 1BL/1RS translocation between wheat and rye, which has been widely utilized in wheat breeding programs (Wang et al., 2014). Additionally, studies on synthetic Arabidopsis allopolyploids have shown that genomic remodeling, including the activation of transposons and chromosomal fragment formation, can occur post-polyploidization, contributing to phenotypic instability and reduced fertility (Madlung et al., 2004). Environmental factors also significantly influence chromosomal rearrangements in polyploid Triticeae species. Research on Kengyilia thoroldiana has demonstrated that populations from different environments exhibit varying frequencies of chromosome translocations, with higher rates observed in cold alpine and grassland environments compared to valley and lake-basin habitats (Wang et al., 2012). This suggests that environmental stress can exacerbate genomic shock, leading to increased chromosomal rearrangements and potentially driving the evolution of new ecotypes. 3.2 Gene duplication and its contribution to functional diversity inTriticeae Gene duplication is a fundamental outcome of polyploidization, providing raw material for evolutionary innovation and functional diversification. In Triticeae, gene duplication resulting from polyploidization can lead to the development of novel gene functions and increased genetic diversity. For example, the process of homoeologous recombination in allopolyploids can generate new gene combinations and phenotypes, although it may also destabilize the karyotype and reduce fertility (Gaeta and Pires, 2010). This recombination-driven genetic variation is crucial for the adaptation and evolution of polyploid species. Moreover, polyploidization-induced gene duplication can result in subfunctionalization, where duplicated genes diverge and specialize in different functions. This phenomenon has been observed in various plant polyploids, including Triticeae, where dynamic changes in gene expression and genomic organization occur post-polyploidization (Chen, 2007). These changes can lead to the emergence of new traits and improved adaptability, contributing to the success of polyploid species in diverse environments. 3.3 Epigenetic modifications and polyploid stability inTriticeae genomes Epigenetic modifications play a vital role in maintaining genome stability and regulating gene expression in polyploid Triticeae. Polyploidization often triggers epigenetic changes, such as DNA methylation and histone modifications, which can influence gene expression and phenotypic variation. For instance, studies on synthetic plant allopolyploids have documented extensive changes in cytosine methylation and chromatin modifications, which are associated with gene repression, novel activation, and transposon activity (Chen and Ni, 2006). These epigenetic alterations help establish a compatible relationship between the divergent genomes in allopolyploids, facilitating their stabilization and evolution. Furthermore, epigenetic mechanisms are crucial for the long-term stability of polyploid genomes. Research on natural allotetraploid Brachypodium hybridum has shown that while immediate genomic shock may not always occur, gradual epigenetic changes over evolutionary time contribute to genome diploidization and stability (Scarlett et al., 2022). These findings highlight the importance of epigenetic modifications in the adaptive evolution and domestication of polyploid Triticeae species, enabling them to thrive in various environmental conditions (Chen, 2007). 4 Polyploidy and Agronomic Trait Improvement inTriticeae 4.1 Polyploidy-driven enhancement of yield, drought tolerance, and disease resistance inTriticeae Polyploidy has been shown to significantly enhance various agronomic traits in Triticeae, including yield, drought tolerance, and disease resistance. The induction of polyploidy can lead to increased biomass yield and improved stress tolerance. For instance, polyploid plants often exhibit enhanced tolerance to abiotic and biotic stresses, which can positively impact plant growth and net production (Tossi et al., 2022). Additionally, polyploidy can result in larger plant organs and increased cell size, which may contribute to higher yield potential (Corneillie et al., 2018). The genetic and physiological changes induced by polyploidy, such as increased gene expression and genome reorganization, are crucial for these improvements (Renny-Byfield and Wendel, 2014).
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