Triticeae Genomics and Genetics, 2024, Vol.15, No.4, 206-220 http://cropscipublisher.com/index.php/tgg 215 develop wheat varieties with improved resistance to various biotic stresses, including rusts, septoria, and fusarium head blight (Ogbonnaya et al., 2013). The breeding programs in India have focused on utilizing SHWs to pyramid QTLs for resistance to multiple pests and pathogens. This approach has led to the development of wheat varieties with enhanced resistance to biotic stresses and improved yield potential. The success of these breeding efforts underscores the value of SHWs in addressing the challenges posed by pests and pathogens in wheat cultivation (Ogbonnaya et al., 2013). Moreover, the integration of SHWs into Indian breeding programs has resulted in the development of high-yielding wheat varieties that are well-adapted to local environmental conditions. The genetic diversity and novel alleles introduced by SHWs have played a crucial role in enhancing the yield potential and stress tolerance of these wheat varieties, contributing to the overall improvement of wheat productivity in India (Ogbonnaya et al., 2013). In conclusion, the case studies from CIMMYT Mexico, Southwest China, and India demonstrate the significant impact of synthetic hexaploid wheat in breeding programs. The genetic diversity and novel traits introduced by SHWs have led to the development of high-yielding, disease-resistant wheat varieties, highlighting the potential of SHWs to improve wheat productivity and resilience to biotic and abiotic stresses globally. 8 Challenges and Limitations 8.1 Technical and logistical challenges Leveraging genetic diversity from synthetics for wheat improvement presents several technical and logistical challenges. One of the primary technical hurdles is the complexity of chromosome engineering, which involves the incorporation of targeted chromosomal segments from wild relatives into wheat chromosomes. This process, although promising, requires advanced cytogenetic methodologies and precise manipulation of genomes, which can be technically demanding and resource-intensive. Additionally, the introgression of exotic germplasm often brings along undesirable traits, making direct use in breeding programs difficult. This necessitates the development of sophisticated genomic selection approaches to enable rapid cycles of selection, which can be restricted by complex physiological effects (Dunckel et al., 2017). Logistically, the process of identifying and mobilizing useful genetic variation from germplasm banks to breeding programs is a significant challenge. The vast diversity within gene banks requires extensive screening and evaluation to identify beneficial traits, which is both time-consuming and labor-intensive (Sehgal et al., 2015). Furthermore, the production and maintenance of synthetic hexaploid wheats (SHWs) involve intricate breeding strategies and large-scale field trials to assess their performance under various environmental conditions, adding to the logistical burden (Ogbonnaya et al., 2013). 8.2 Genetic stability and performance issues The genetic stability and performance of synthetic-derived wheat lines are critical concerns. While SHWs are valuable for introducing new genes for stress resistance and yield improvement, they often exhibit genetic instability due to the complex interactions between the introduced and native genomes. This instability can lead to unpredictable performance in different environments, posing a challenge for breeders (Mujeeb-Kazi et al., 2015). Moreover, the recombination and reassortment within the synthetic genomes can generate novel gene combinations, but these may not always result in desirable agronomic traits, necessitating further selection and breeding efforts (Wan et al., 2023). Another issue is the potential for linkage drag, where undesirable traits are co-inherited with beneficial ones, complicating the breeding process. This is particularly problematic when dealing with genes from the tertiary gene pool, which often involve intergeneric crosses and can result in significant genetic incompatibilities (Mujeeb-Kazi et al., 2015). Additionally, the introgression of exotic alleles can sometimes lead to reduced fitness or adaptability in the target environment, requiring careful management and selection to ensure stable performance (Hao et al., 2019).
RkJQdWJsaXNoZXIy MjQ4ODYzNQ==