Genomics and Applied Biology 2024, Vol.15, No.3, 162-171 http://bioscipublisher.com/index.php/gab 163 2 Genetic Basis of Hybrid Kelp 2.1 Overview of kelp genetics Kelp, a type of large brown algae, has a complex genetic structure that is crucial for its adaptation and survival in various marine environments. The genetic improvement of kelp has been a focus in regions like Asia, where heterosis (hybrid vigor) has been utilized to enhance productivity and quality (Goecke et al., 2020). The genetic architecture of kelp involves both sporophyte and gametophyte generations, which alternate in their life cycle, providing unique opportunities for genetic studies and breeding (Zhang et al., 2015). 2.2 Genetic diversity in kelp populations Genetic diversity is a critical factor for the resilience and adaptability of kelp populations. Studies have shown that wild kelp populations exhibit higher genetic diversity compared to cultivated ones, which is essential for maintaining the ecological balance and potential for future breeding programs. For instance, the genetic diversity of Saccharina japonica has been significantly affected by domestication, leading to distinct genetic pools between wild and cultivated populations (Zhang et al., 2017). Additionally, regional genetic differences have been observed, such as between the Gulf of Maine and Southern New England populations of sugar kelp, which are separated by biogeographic barriers (Mao et al., 2020). 2.3 Hybridization techniques in kelp breeding Hybridization is a key technique in kelp breeding, aimed at combining desirable traits from different species or populations. Techniques such as recurrent mixed hybridization and phenotypic selection have been proposed to enhance kelp breeding (Goecke et al., 2020). In China, hybridization-based breeding pipelines have been optimized to produce robust cultivars by introgressing novel alleles and expressing hybrid vigor (Hu et al., 2023). Intergeneric hybridization has also been explored, although it requires careful molecular confirmation to ensure the persistence and normal development of hybrid sporophytes (Druehl et al., 2005). 2.4 Molecular markers and genomic tools in kelp hybridization The development of molecular markers and genomic tools has significantly advanced kelp hybridization efforts. High-density SNP linkage maps and RAD sequencing have been employed to identify genetic loci associated with important traits, such as sex determination and morphological characteristics (Zhang et al., 2015). Additionally, genome-wide markers have been used to assess population structure and detect selection signatures, providing valuable insights for selective breeding (Mao et al., 2020). The use of SSR markers has also been instrumental in understanding the genetic impact of domestication on kelp populations (Zhang et al., 2017). 2.5 Case studies on hybrid kelp breeding Several case studies highlight the success and challenges of hybrid kelp breeding. For example, interfamilial hybridization between Macrocystis pyrifera and Lessonia spicata has been confirmed through morphological, genotypic, and metabolomic analyses, demonstrating the potential for hybrid vigor in natural populations (Murúa et al., 2020) (Figure 1). Another study on Laminaria digitata and L. pallida revealed that interspecific hybrids exhibited higher thermal tolerance compared to their parental species, indicating heterosis for thermal resilience (Martins et al., 2019). These case studies underscore the importance of hybridization in enhancing the adaptability and performance of kelp under changing environmental conditions. 3 Breeding Strategies for Hybrid Kelp 3.1 Traditional breeding methods Traditional breeding methods for kelp involve the selection and recombination of desirable traits through controlled mating and hybridization. This approach has been widely used in Asia, where the genetic improvement of kelp has largely relied on the utilization of heterosis, or hybrid vigor, expressed in certain combinations of parental material, including species hybrids. The process typically involves recurrent mixed hybridization and phenotypic selection within local populations to enhance productivity and product quality (Goecke et al., 2020). However, traditional methods face challenges such as genetic erosion and loss of heterozygosity due to repeated selection and self-crossing (Hu et al., 2023).
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