Triticeae Genomics and Genetics, 2024, Vol.15, No.5, 244-254 http://cropscipublisher.com/index.php/tgg 248 4.2 Genetic and phenotypic consequences of polyploidy on plant height, flowering time, and grain quality Polyploidy can lead to significant genetic and phenotypic changes in Triticeae, affecting traits such as plant height, flowering time, and grain quality. Polyploid plants often exhibit delayed flowering and increased plant height due to changes in cell size and number (Corneillie et al., 2018). These changes can be attributed to the increased DNA content and altered gene expression patterns in polyploids (Balao et al., 2011). Moreover, polyploidy can influence grain quality by modifying the composition of bioactive compounds and altering metabolic pathways (Tavan et al., 2021). For example, polyploidy has been associated with changes in cell wall composition and sugar content, which can affect grain quality and processing characteristics (Corneillie et al., 2018). 4.3 Breeding strategies leveraging polyploid traits for crop improvement Breeding strategies that leverage polyploid traits can significantly enhance crop improvement efforts in Triticeae. The use of synthetic polyploids and grafted crops can provide specific advantages, such as improved stress tolerance and yield. Breeding programs can exploit the genetic diversity and novel traits introduced by polyploidy to develop superior cultivars. For instance, the induction of polyploidy in rootstocks can enhance adaptation to biotic and abiotic stresses, while maintaining high yield and quality in the scion (Ruiz et al., 2022). Additionally, modern technologies, such as next-generation sequencing, can facilitate the identification and manipulation of polyploid traits, enabling more efficient breeding strategies (Renny-Byfield and Wendel, 2014). The integration of polyploidy into breeding programs holds great potential for the development of resilient and high-yielding Triticeae crops. 5 Gene Expression Modulation in PolyploidTriticeae 5.1 Subgenome interaction and differential gene expression in polyploid wheat and barley Polyploidy in Triticeae, particularly in wheat and barley, results in complex interactions between subgenomes that significantly influence gene expression. In hexaploid wheat, the presence of three subgenomes (A, B, and D) leads to nonbalanced expression patterns in approximately 30% of homoeologous gene triads, with one homoeolog often showing higher or lower expression relative to the others. This differential expression is associated with epigenetic changes such as DNA methylation and histone modifications, and is influenced by the presence of transposable elements in gene promoters. Additionally, the transcriptional landscape of polyploid wheat reveals that homoeologous genes exhibit tissue-specific expression patterns, which are crucial for the plant's development and stress responses (Ramírez-González et al., 2018). The interaction between subgenomes also manifests in the form of gene dosage effects, where the deletion or addition of chromosomes in nullisomic-tetrasomic stocks leads to genome-wide changes in gene expression, affecting traits such as plant height and kernel number (Zhang et al., 2019). 5.2 Role of non-homoeologous recombination in modulating agronomically important traits Non-homoeologous recombination plays a pivotal role in the genetic innovation and adaptation of polyploid Triticeae. In wheat, illegitimate recombination between homoeologous genes can lead to gene conversion events, which contribute to genome instability but also drive functional and structural innovation. This process affects a significant number of genes, including those involved in starch biosynthesis, thereby influencing important agronomic traits (Figure 2) (Liu et al., 2020). Moreover, the structural organization of chromosomes, including truncations and rearrangements, can modulate recombination frequencies, particularly in crossover-poor regions, enhancing the transfer of beneficial traits into crops (Naranjo, 2019). These recombination events are crucial for the introgression of useful genes and the overall improvement of crop performance. Liu et al. (2020) revealed the evolutionary branches of homoeologous genes in Triticeae species and the conservation and diversity of genes across different subgenomes during polyploid evolution. Non-homologous recombination plays a critical role in regulating key agronomic traits, such as starch biosynthesis, in crops like wheat. This genetic diversity allows for functional complementation between different subgenomes, giving polyploid plants an advantage in adaptability and growth performance. This study provides an important theoretical foundation for understanding the genetic improvement of essential crops like wheat, aiding in the enhancement of crop yield and quality through molecular breeding methods.
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