Molecular Plant Breeding 2024, Vol.15, No.6, 362-370 http://genbreedpublisher.com/index.php/mpb 367 6 Challenges and Limitations in Hybrid Sorghum Breeding 6.1 Environmental and biotic stress factors Hybrid sorghum breeding faces significant challenges due to environmental and biotic stress factors. Variability in weather patterns, such as those observed in Australia, can lead to substantial differences in yield between locations, complicating the prediction of hybrid performance (Hunt et al., 2020). Additionally, genotype-by-environment (G×E) interactions significantly affect yield stability, as seen in biomass sorghum hybrids, where factors like precipitation, temperature, and wind speed play crucial roles (Oliveira et al., 2020). Drought and grain mold are also major constraints, impacting both production and productivity (Kumar et al., 2021). In the Great Plains region of the United States, water-deficit and heat stress patterns further complicate breeding efforts, necessitating a better definition of target environments to improve predictability and genetic gains (Carcedo et al., 2022). 6.2 Genetic constraints and breeding efficiency Genetic constraints and breeding efficiency are critical limitations in hybrid sorghum breeding. The lack of quantitative genetic information about the genetic value of new hybrids and their parents, especially under low-input conditions, hampers the development of high-yielding varieties (Kante et al., 2019). Genomic prediction models have shown promise in improving selection efficiency, but the accuracy of these models varies significantly depending on the traits and the size of the training population (Maulana et al., 2023). Moreover, the interplay between local adaptation and G×E interactions can lead to maladaptive phenotypic plasticity, affecting heterosis estimates and breeding outcomes (Otwani et al., 2023). The complexity of genetic mechanisms underlying specific traits, such as semolina recovery, also poses challenges for breeding genotypes with desired end-use qualities (Suguna et al., 2021). 6.3 Market acceptance and commercialization barriers Market acceptance and commercialization barriers are significant hurdles in the adoption of new hybrid sorghum varieties. Despite the potential benefits of hybrid sorghum, such as higher yields and improved stress tolerance, the uptake of hybrid seeds remains low in many developing countries (Otwani et al., 2023). This low adoption rate can be attributed to several factors, including the lack of awareness among farmers, limited access to high-quality seeds, and the absence of robust market infrastructure to support the commercialization of new varieties. Additionally, the trade-offs between agronomic performance and yield stability, as observed in dual-purpose sorghum genotypes in Senegal, can affect market acceptance, as farmers may prefer stable yields over high but variable performance (Ndiaye et al., 2019). 7 Concluding Remarks The breeding of new hybrid sorghum varieties has shown significant promise in enhancing yield performance across various environments and conditions. Sorghum hybrids, particularly those developed from Guinea-race parents, demonstrated substantial yield advantages over local varieties. For instance, hybrids showed 20% to 80% higher yields under both low-phosphorus (LP) and high-phosphorus (HP) conditions in West Africa. Similarly, hybrids based on Guinea-race germplasm exhibited 17% to 37% yield superiority over traditional landrace cultivars in Mali. The use of diverse unadapted germplasm in breeding programs has been effective in introducing new alleles and retaining genetic variation, which is crucial for future genetic gains. This approach has led to the identification of progeny that outperform recurrent parent hybrids for grain yield. Combining ability analysis has also identified promising parent lines that can be used to develop hybrids with high yield, earliness, and ideal plant height. The stability and adaptability of new sorghum varieties have been evaluated using AMMI and GGE biplot analyses. These methods have identified high-yielding, stable varieties that perform well across multiple environments, despite genotype × environment interactions. Genomic selection has been shown to improve the efficiency of predicting hybrid performance based on parental genotypes. This method has demonstrated high prediction accuracies for grain yield, suggesting its potential as a valuable tool in sorghum breeding programs.
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