Triticeae Genomics and Genetics, 2024, Vol.15, No.2, 100-110 http://cropscipublisher.com/index.php/tgg 105 considerations include the potential for unintended consequences, such as the loss of genetic diversity in wild populations and the ethical implications of manipulating plant genomes (Pershina and Trubacheeva, 2017; Alvarez and Guzmán, 2018). These considerations necessitate a careful and balanced approach to the use of wide hybridization in wheat breeding. 7 Case Studies of Wide Hybridization in Wheat 7.1 Successful examples in wheat breeding programs Wide hybridization has been an essential tool for introducing new genetic variations and improving various agronomic traits in wheat breeding programs. By crossing with wild relatives and old varieties, wheat quality traits such as grain hardness, gluten quality, and starch content have been improved. This approach has also expanded the nutritional quality of wheat by introducing vitamins, fibers, and micronutrients (Alvarez and Guzmán, 2018). A large-scale GWAS involving 768 wheat varieties identified 395 quantitative trait loci (QTL) for 12 traits. This study highlighted the potential of wide hybridization in identifying candidate genes to improve key traits such as spikelet number and grain size, which are crucial for increasing yield (Figure 2) (Pang et al., 2020). Experiments involving 15 different species from the Poaceae and Panicoideae families demonstrated the feasibility of wide hybridization among wheat, barley, and rye. Successful embryo formation with species such as Agropyron and maize showed the potential for creating new genetic combinations. Studies on wheat hybrid seed set exhibited significant genetic variation and high heritability. By selecting male floral traits such as anther extrusion, breeders can indirectly improve hybrid seed set, thus enhancing the efficiency of hybrid wheat breeding programs (Boeven et al., 2018). A three-step strategy was developed to identify heterotic patterns for high-yield hybrid wheat breeding. This method, which includes genomic prediction and simulated annealing algorithms, showed promise in improving grain yield and stability by leveraging heterosis (Zhao et al., 2015). 7.2 Comparative analysis of different methods Various methods have been explored in wide hybridization of wheat, proving to be very effective in introducing new quality traits and nutritional components. However, careful selection of parental species is required to ensure compatibility and successful hybridization (Alvarez and Guzmán, 2018). GWAS provides a high-resolution method for identifying QTL and candidate genes associated with important agronomic traits. This approach is data-intensive, requiring large populations and high marker density for accurate results (Pang et al., 2020). Wide hybridization experiments demonstrated that embryo culture techniques could facilitate the growth of haploid and diploid embryos from multiple species. This method is crucial for overcoming hybridization barriers and ensuring the development of viable plants. Indirect selection of traits such as anther extrusion can improve hybrid seed set, making this a practical method for enhancing the efficiency of hybrid wheat breeding. However, it requires a deep understanding of the genetic architecture of these traits (Boeven et al., 2018). The three-step strategy for identifying heterotic patterns combines genomic prediction and advanced algorithms to optimize hybrid performance. This method is highly effective but requires substantial computational resources and expertise in genomics (Zhao et al., 2015). 7.3 Lessons learned and best practices Utilizing a broad genetic base, including wild relatives and old varieties, can significantly enhance the genetic diversity and quality traits of wheat (Alvarez and Guzmán, 2018). Employing high-resolution mapping techniques such as GWAS can identify key QTL and candidate genes, facilitating targeted breeding efforts (Figure 3) (Pang et al., 2020). Developing and refining embryo culture techniques are crucial for the success of wide hybridization, especially when dealing with distant species. Focusing on indirect traits related to desired outcomes, such as anther extrusion for hybrid seed set, can simplify the breeding process and improve efficiency (Boeven et al., 2018). Implementing structured approaches to identify and exploit heterotic patterns can maximize the benefits of heterosis and enhance yield stability (Zhao et al., 2015). By integrating these best practices, wheat breeding
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