Triticeae Genomics and Genetics, 2024, Vol.15, No.3, 152-161 http://cropscipublisher.com/index.php/tgg 157 In summary, the utilization of exotic germplasm in wheat breeding has led to significant advancements in disease resistance, abiotic stress tolerance, and yield improvement. The integration of advanced breeding strategies and genomic tools has further enhanced the efficiency and effectiveness of these efforts, paving the way for the development of resilient and high-yielding wheat varieties. 5 Challenges and Solutions 5.1 Barriers to the use of exotic germplasm One of the primary challenges in utilizing exotic germplasm for wheat improvement is genetic incompatibility. Exotic germplasm often contains genetic variations that are not easily compatible with the genetic makeup of elite wheat cultivars. This incompatibility can result in reduced fertility, poor agronomic performance, and other undesirable traits when attempting to introgress beneficial alleles from exotic sources into modern wheat varieties (Zhou et al., 2021; Chidzanga et al., 2021; Sharma et al., 2021). Linkage drag is another significant barrier, where undesirable traits are co-inherited with beneficial alleles due to their close proximity on the chromosome. This phenomenon complicates the breeding process as it requires additional steps to separate the beneficial traits from the undesirable ones, thereby prolonging the breeding cycle and reducing efficiency (Chidzanga et al., 2021; Sharma et al., 2021; Cheng et al., 2023). 5.2 Strategies to overcome challenges To address genetic incompatibility and linkage drag, advanced breeding techniques such as marker-assisted selection (MAS) and genomic selection (GS) are employed. These techniques allow for the precise identification and selection of beneficial alleles while minimizing the co-introduction of undesirable traits. For instance, the use of nested association mapping (NAM) populations has been shown to effectively incorporate genetic diversity and dissect complex traits, thereby facilitating the introgression of beneficial alleles into elite wheat backgrounds (Molero et al., 2018; Chidzanga et al., 2021 Cheng et al., 2023). Genomic and bioinformatics approaches play a crucial role in overcoming the challenges associated with the use of exotic germplasm. High-throughput sequencing and genotyping technologies enable the detailed characterization of genetic diversity and the identification of key genomic regions associated with desirable traits. For example, the construction of high-quality reference genomes and the development of genomic variation landscapes provide valuable resources for gene discovery and breeding (Sansaloni et al., 2020; Zhou et al., 2021; Yang et al., 2022). Additionally, bioinformatics tools such as ggComp facilitate the precise evaluation of germplasm resources, enabling the identification of beneficial alleles and their strategic introgression into modern wheat varieties (Joynson et al., 2020; Yang et al., 2022). By leveraging these advanced techniques and approaches, the barriers to the use of exotic germplasm can be effectively mitigated, thereby enhancing the genetic diversity and overall resilience of wheat cultivars. 6 Future Prospects and Research Directions 6.1 Emerging trends in germplasm utilization The utilization of exotic germplasm in wheat breeding is gaining momentum as researchers recognize the potential of wild relatives to enhance genetic diversity and improve crop resilience. Recent studies have demonstrated the successful introgression of Aegilops tauschii into wheat, enriching the genetic pool and providing valuable traits for breeding programs (Gorafi et al., 2018; Aberkane et al., 2020; Zhou et al., 2021). The development of synthetic hexaploid wheat (SHW) has been particularly noteworthy, with significant contributions to yield potential and stress tolerance (Hao et al., 2019; Afzal et al., 2019; Rosyara et al., 2019). The integration of advanced genomic tools, such as genome-wide association studies (GWAS) and haplotype-based approaches, is further refining the precision of germplasm utilization, enabling the identification of beneficial alleles and their targeted incorporation into breeding lines (Afzal et al., 2019 Balla et al., 2022). 6.2 Potential of synthetic wheats Synthetic wheats, particularly those derived from Aegilops tauschii, have shown immense potential in wheat improvement. These synthetic derivatives have been instrumental in introducing novel genetic variations that
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