Triticeae Genomics and Genetics, 2024, Vol.15, No.4, 196-205 http://cropscipublisher.com/index.php/tgg 200 4.3.2 Breeding for climate resilience Breeding for climate resilience in wheat involves the incorporation of genes that confer tolerance to abiotic stresses such as drought and heat. The use of SHW has been instrumental in this regard, as it combines the genetic diversity of wild relatives with the adaptability of modern wheat varieties. For instance, SHW lines have been developed with traits such as early vigour and enhanced biomass, which are crucial for resilience under changing climatic conditions (Yang et al., 2020). The integration of these traits into breeding programs aims to produce wheat cultivars that can withstand the challenges posed by climate change (Aberkane et al., 2020). 5 Case Studies and Applications 5.1 Successful breeding programs 5.1.1 High-yielding varieties The development of synthetic hexaploid wheat (SHW) has significantly contributed to the creation of high-yielding wheat varieties. For instance, the breeding strategy involving the large population with limited backcrossing method' has successfully pyramided stripe rust resistance and big-spike-related QTLs/genes from SHW into new high-yield cultivars. This approach has led to the creation of record-breaking high-yield wheat in southwestern China (Wan et al., 2023). Additionally, the derivatives of goat grass (Aegilops tauschii) have been used to widen the genetic base for wheat breeding, resulting in high yield potential and good quality attributes in SHW-derived lines (Aberkane et al., 2020). 5.1.2 Disease-resistant varieties SHW has also been instrumental in developing disease-resistant wheat varieties. For example, the SynDT line, a SHW developed in Korea, exhibits resistance to leaf rust by inducing the expression of antifungal enzymes and pathogen-related genes (Truong et al., 2020). Moreover, SHW has shown effective resistance to tan spot, a significant foliar disease, with 233 out of 443 SHW plants evaluated showing resistant reactions (Lozano-Ramírez et al., 2022). These disease-resistant varieties are crucial for maintaining wheat production in the face of biotic stress. 5.2 Role of international collaboration 5.2.1 Collaborative research projects International collaboration has played a pivotal role in the development and dissemination of SHW. The International Maize and Wheat Improvement Center (CIMMYT) has been at the forefront, distributing over 10,000 samples of SHW to 110 institutions in 40 countries between 2000 and 2018. This collaborative effort has led to the release of at least 86 SHW-derived varieties in 20 countries, demonstrating the global impact of SHW on wheat breeding (Aberkane et al., 2020). Additionally, genome-wide association studies involving multiple international research teams have identified significant marker-trait associations for disease resistance, further enhancing the utility of SHW in breeding programs (Lozano-Ramírez et al., 2022). 5.2.2 Global genebank utilization The utilization of global genebanks has been essential in the development of SHW. For instance, 629 unique accessions from 15 countries were used for pre-breeding, producing 1577 primary SHWs. These genebank resources have been crucial in transferring desirable traits from wild relatives into modern wheat varieties, thereby enhancing genetic diversity and resilience (Aberkane et al., 2020). The extensive use of genebank collections underscores the importance of international cooperation in leveraging genetic resources for wheat improvement. 6 Challenges and Future Perspectives 6.1 Genetic bottlenecks and diversity loss 6.1.1 Causes of genetic erosion Genetic erosion in wheat breeding is primarily caused by the narrow genetic base of modern wheat varieties, which results from intensive selection and breeding practices aimed at improving specific traits such as yield, disease resistance, and quality. This has led to the loss of genetic diversity, making wheat crops more vulnerable to biotic and abiotic stresses (Sansaloni et al., 2020; Yang et al., 2022). The domestication and modern breeding of wheat have significantly reduced the genetic variation present in wild relatives and landraces, which are crucial reservoirs of alleles for stress tolerance and other beneficial traits (Aberkane et al., 2020; Ullah et al., 2020).
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