Bioscience Evidence 2024, Vol.14, No.5, 195-205 http://bioscipublisher.com/index.php/be 197 Recent advancements have introduced genetic systems for pollination control, such as the split-gene system, which relies on the expression of a phytotoxic barnase to induce male sterility. This system allows for the maintenance of male-sterile lines and the production of hybrid seeds without the need for fertility restorers (Kempe et al., 2014). However, these systems still face challenges, including the potential for incomplete sterility and the need for precise genetic manipulation. Overcoming these limitations requires continued innovation in genetic engineering and breeding techniques to develop more reliable and efficient male sterility systems for hybrid wheat production. 3 Technological Advances in Overcoming Hybridization Barriers 3.1 Cytoplasmic and nuclear male sterility Cytoplasmic male sterility (CMS) systems have been a cornerstone in the development of hybrid wheat varieties. CMS is a maternally inherited trait that results in the inability of plants to produce functional pollen, thus facilitating cross-pollination. The S type of CMS in wheat, derived fromAegilops species, has been extensively studied and utilized. However, practical application has faced challenges such as limited restoration resources and lower germination rates (Wang et al., 2013). Recent advancements have identified specific genes, such as Rf1 and Rf3, which can restore fertility in CMS lines by binding to mitochondrial transcripts and preventing the expression of the sterility trait (Figure 1) (Melonek et al., 2021). This genetic understanding is crucial for developing more efficient CMS-based hybridization systems. Figure 1 Evaluation of fertility restoration byRf1andRf3genes in Fielder*CMS lines (Adapted from Melonek et al., 2021) Image caption: A: Design of constructs used in the transgenic experiment, covering wheat candidate restorer genes (Rf1 and Rf3) and their expression regulatory elements; B: Evaluation of fertility restoration rates in T0 plants restored with different gene constructs; C: Transgenic expression levels obtained through RNA-Seq (TPM); D: Pollen morphology of restored transgenic plants shown through Alexander staining; E: Pollen viability statistics; F: Assessment of the number of seeds per spike in transgenic plants (Adapted from Melonek et al., 2021)
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