Bioscience Evidence 2024, Vol.14, No.5, 195-205 http://bioscipublisher.com/index.php/be 198 In the study by Melonek et al. (2021), the fertility restoration effect was evaluated by introducing the restorer genes Rf1 and Rf3, either individually or in combination, into the CMS wheat sterile line Fielder*. The transgenic lines successfully expressed the restorer genes and exhibited significant improvements in pollen morphology, viability, and the number of seeds per spike. The results indicated that Rf79 made a considerable contribution to fertility restoration, either alone or in combination with other genes. Nuclear male sterility (NMS) systems offer an alternative to CMS by using nuclear genes to control male fertility. For instance, the barnase gene, when expressed under tapetum-specific promoters, can induce male sterility in wheat (Block et al., 1997). This method allows for precise control over male fertility and can be integrated into hybrid breeding programs. The development of NMS systems, such as those involving the Ms1, Ms5, TaMs26, and TaMs45 genes, has shown promise in creating stable and efficient hybridization platforms (Singh et al., 2021). These systems can potentially lower the cost of hybrid seed production and enhance the commercial viability of hybrid wheat varieties. 3.2 Embryo rescue techniques Embryo rescue is a critical technique in overcoming post-fertilization barriers in wheat hybridization. This method involves the in vitro culture of embryos that would otherwise abort due to incompatibilities between the parental genomes. Embryo rescue has been successfully used to produce hybrids between wheat and its wild relatives, thereby introducing beneficial traits such as disease resistance and abiotic stress tolerance into cultivated wheat varieties. The technique has evolved with advancements in tissue culture and molecular biology. For example, the optimization of culture media and growth conditions has significantly improved the success rates of embryo rescue. Additionally, the use of molecular markers to select viable embryos at an early stage has streamlined the process, making it more efficient and reliable. These improvements have expanded the potential of embryo rescue in wheat breeding programs, enabling the incorporation of a wider range of genetic diversity into commercial wheat varieties. 3.3 Gene editing (CRISPR/Cas9) Gene editing technologies, particularly CRISPR/Cas9, have revolutionized the field of plant breeding by enabling precise modifications to the genome. In wheat, CRISPR/Cas9 has been used to target genes associated with male sterility and fertility restoration, thereby facilitating hybridization (Ma and Cai, 2024). For instance, the targeted mutagenesis of genes such as Ms1 and TaMs45 has been shown to induce male sterility, which is essential for hybrid seed production (Singh et al., 2021). CRISPR/Cas9 offers several advantages over traditional breeding methods. It allows for the introduction of specific genetic changes without the need for extensive backcrossing, thereby accelerating the breeding process. Moreover, the ability to multiplex CRISPR/Cas9, i.e., target multiple genes simultaneously, provides a powerful tool for manipulating complex traits such as male fertility. This technology holds great promise for overcoming biological barriers in wheat hybridization and enhancing the efficiency and precision of hybrid breeding programs. 4 Application and Progress of Genomic and Molecular Tools in Wheat Hybridization 4.1 Marker-assisted selection (MAS) Marker-Assisted Selection (MAS) has revolutionized wheat breeding by enabling the precise selection of desirable traits through the use of DNA markers. This technique allows breeders to identify and select plants carrying specific genes associated with beneficial traits, thereby accelerating the breeding process and improving the efficiency of developing hybrid wheat varieties (Wu, 2024). MAS has been particularly effective in incorporating traits such as disease resistance, yield potential, and quality characteristics into new wheat hybrids. The development of high-density genetic maps and the identification of quantitative trait loci (QTLs) have been instrumental in the success of MAS in wheat breeding programs (Collard et al., 2005; Paux et al., 2012; Rathan et al., 2023).
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