Triticeae Genomics and Genetics, 2024, Vol.15, No.5, 255-265 http://cropscipublisher.com/index.php/tgg 259 These changes result in heritable epialleles. These epialleles can be used in wheat breeding to target traits such as stress resistance, yield, and quality improvement. As a result, epigenetic breeding represents an emerging strategy for crop improvement, particularly suited to addressing complex environmental challenges such as climate change. 5 The Role of Epigenetics in Wheat Stress Resistance Traits 5.1 Epigenetic regulation of drought resistance traits Epigenetic mechanisms, such as DNA methylation, play a crucial role in regulating gene expression in response to drought stress in wheat. For instance, the TaBADH-A1 gene, which is involved in osmotic regulation, shows significant expression differences under drought conditions. Wheat cultivars with the BADH-A1b allele exhibit higher expression levels and better drought tolerance compared to those with the BADH-A1a allele, highlighting the importance of epigenetic regulation in drought resistance (Yu et al., 2022). Additionally, plant growth-promoting rhizobacteria (PGPR) have been shown to enhance drought tolerance by modulating the expression of stress-related genes, such as TaDREB2, through epigenetic mechanisms (Barnawal et al., 2017). A specific case study on the TaBADH-A1 gene demonstrated the potential of DNA methylation in enhancing drought tolerance in wheat. The BADH-A1b allele, associated with higher betaine accumulation, exhibited increased expression under drought stress, leading to improved germination and survival rates. This allele is considered a strong candidate for marker-assisted selection in breeding programs for drought-tolerant wheat varieties. Yu et al. (2022) analyzed the tolerance of different TaBADH-A1 alleles in wheat recombinant inbred lines under drought and salt stress. The results showed that plants containing the BADH-A1b allele (lines 6–10) had significantly higher survival rates under drought and salt stress compared to plants with the BADH-A1a allele (lines 1–5), indicating that the BADH-A1b allele may confer stronger stress resistance (Figure 2). This study provides important evidence for improving drought and salt tolerance in wheat through gene selection, with potential agricultural applications. Additionally, the introduction of the stress-responsive gene SNAC1 from rice into wheat enhanced drought tolerance through epigenetic regulation, further supporting the key role of DNA methylation in stress resistance (Saad et al., 2013). 5.2 Epigenetic mechanisms of salt and alkaline stress resistance Salt stress is another major challenge for wheat cultivation, and epigenetic modifications, such as cytosine methylation, have been shown to regulate the expression of key genes involved in salt tolerance. For example, the differential expression of HKT genes, regulated by cytosine methylation, contributes to salt tolerance in wheat. In salt-tolerant genotypes, increased methylation of TaHKT2;1 and TaHKT2;3 genes leads to their downregulation, thereby enhancing salt tolerance (Kumar et al., 2017a; Kumar et al., 2017b). Additionally, the WRKY transcription factors, such as TaWRKY93 and TaWRKY75-A, are regulated epigenetically and play significant roles in mediating salt stress responses by enhancing osmotic adjustment and maintaining membrane stability (Qin et al., 2015; Ye et al., 2021). 5.3 Epigenetics in response to temperature stress Temperature stress, including both high and low temperatures, affects wheat growth and productivity. Epigenetic mechanisms, such as the regulation of transcription factors, are crucial in mediating temperature stress responses. For instance, the overexpression of TaWRKY93 in Arabidopsis has been shown to enhance tolerance to low temperature stress by upregulating stress-related genes and maintaining higher relative water content and membrane stability (Qin et al., 2015). Similarly, the MYB transcription factor TaMYBsdu1 is differentially regulated under temperature stress, with higher expression levels observed in stress-tolerant genotypes, indicating its potential role in temperature stress adaptation (Rahaie et al., 2010). 6 Potential of Combining Epigenetic Modifications with Wheat Breeding 6.1 Application of epigenetic markers in breeding Epigenetic markers, such as DNA methylation and histone modifications, have emerged as valuable tools in wheat breeding. These markers can influence gene expression without altering the underlying DNA sequence, providing an additional layer of genetic regulation that can be harnessed for crop improvement. The use of epigenetic markers allows breeders to predict plant performance and increase crop production by taking into account
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