Cotton Genomics and Genetics 2024, Vol.15, No.2, 93-102 http://cropscipublisher.com/index.php/cgg 98 the divergent improvement of G. hirsutumand G. barbadense (Fang et al., 2021; Wang et al., 2022). Moreover, the introgression of adaptive genes has been shown to be environment-dependent, with specific alleles being favored under certain environmental conditions, thereby aiding in the adaptation to changing climates (Khodwekar and Gailing, 2017). Interspecific introgression has been a pivotal mechanism in the adaptation and improvement of Gossypiumspecies, with historical and modern examples demonstrating its significant impact on genetic diversity, agronomic traits, and environmental adaptation. The continued study and utilization of introgression in cotton breeding hold promise for further advancements in crop performance and resilience. 5 Adaptive Benefits of Interspecific Introgression 5.1 Enhanced abiotic stress tolerance Interspecific introgression has been shown to significantly enhance abiotic stress tolerance in Gossypiumspecies. For instance, introgression fromGossypium hirsutuminto Gossypium barbadense has led to the identification of loci associated with adaptation to high-latitude environments, which are indicative of improved tolerance to abiotic stresses such as temperature extremes (Wang et al., 2022). Additionally, the introgression of genetic material fromG. arboreuminto G. hirsutumhas revealed potential for improving traits related to abiotic stress resilience, such as boll number and fiber quality under varying environmental conditions (Feng et al., 2021). 5.2 Improved biotic resistance Introgression also plays a crucial role in enhancing biotic resistance in Gossypiumspecies. The transfer of genetic material fromG. barbadense to G. hirsutumhas been associated with improved resistance to pests and diseases, which is critical for maintaining crop health and productivity (Zhang et al., 2016). Moreover, the introgression of alleles from G. tomentosum into G. hirsutum has been shown to confer resistance to specific biotic stresses, further highlighting the importance of interspecific gene flow in developing resilient cotton varieties (Waghmare et al., 2016; Keerio et al., 2018). 5.3 Increased yield and fiber quality One of the most significant benefits of interspecific introgression is the improvement in yield and fiber quality. Studies have demonstrated that introgression fromG. hirsutumto G. barbadense has led to the identification of loci that significantly enhance fiber yield and quality traits (Nie et al., 2020). Similarly, the development of introgression lines (ILs) fromG. hirsutumand G. barbadense has resulted in hybrids with high heterotic vigor, outperforming their parent cultivars in terms of yield and fiber quality across multiple generations (Zhang et al., 2016). Additionally, introgressed alleles fromG. barbadense have been identified that contribute to superior fiber quality in G. hirsutum, without negatively impacting lint yield (Chen et al., 2018). 5.4 Broadened genetic diversity Interspecific introgression is a powerful tool for broadening the genetic diversity of Gossypium species. The introgression of genetic material from G. hirsutum into G. barbadense has significantly increased the genetic diversity and divergence within G. barbadense populations, which is crucial for the long-term sustainability and adaptability of the species (Wang et al., 2022). Furthermore, the introgression of G. arboreum genes into G. hirsutumhas introduced valuable genetic variation that was previously untapped due to species isolation, thereby enhancing the genetic base available for cotton breeding (Feng et al., 2021). This broadened genetic diversity is essential for developing new cultivars with improved agronomic traits and resilience to environmental changes (Hamilton and Miller, 2016). 6 Molecular and Genomic Insights 6.1 Genomic tools for studying introgression The study of interspecific introgression in Gossypiumspecies has been significantly advanced by the development and application of various genomic tools. High-throughput sequencing technologies, such as Specific Locus Amplified Fragment Sequencing (SLAF-seq), have enabled the identification of single nucleotide polymorphisms (SNPs) across the genome, facilitating the mapping of quantitative trait loci (QTLs) associated with fiber quality
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