Genomics and Applied Biology 2024, Vol.15, No.6, 307-319 http://bioscipublisher.com/index.php/gab 314 Figure 2 Effects of calcium nitrate on pollen germination of genotypes of (a) D. rotundata, (b) D. alata (Adopted from Mondo et al., 2021) 6.2 Potential of integrating genomic selection with speed breeding The integration of GS with speed breeding creates a synergistic approach, often referred to as SpeedGS, which further accelerates breeding cycles. Genomic selection leverages genome-wide markers to predict the breeding value of individuals, enabling selection decisions without the need for full phenotypic data. When combined with speed breeding, GS allows for rapid generation advancement based on genomic predictions, reducing the breeding cycle length and increasing selection intensity (Jighly et al., 2019). SpeedGS has proven effective in crops like wheat and maize, where rapid generation cycling and genomic predictions have resulted in increased genetic gains for traits with low heritability. In yam, integrating SpeedGS could facilitate the selection of complex traits, such as tuber yield and quality, which are difficult to evaluate in traditional breeding due to the long generation time. By using genomic estimated breeding values (GEBVs) to predict the performance of each generation in a speed-breeding setting, breeders can maximize genetic gain per unit of time while bypassing some of the time-consuming field trials. This combination allows for faster development of varieties with improved resilience to stresses and higher yields (Watson, 2019). 6.3 Impact of shortened breeding cycles on genetic gain Shortened breeding cycles have a direct impact on genetic gain by allowing more rapid accumulation of favorable alleles in the breeding population. Traditional breeding approaches, limited by lengthy cycles, can delay the realization of genetic progress, especially for complex traits controlled by multiple genes. However, by reducing the breeding cycle through SpeedGS, breeders can accelerate the rate of genetic improvement, which is essential for achieving high-yield, resilient yam varieties (Das et al., 2020). Studies indicate that SpeedGS increases genetic gain per year by shortening the cycle time and increasing selection intensity, especially for traits with low heritability, such as disease resistance and tuber quality. The rapid cycling enabled by SpeedGS permits breeders to explore broader genetic variability in a shorter time, allowing for faster adaptation to environmental challenges and market demands. However, one challenge of SpeedGS is the potential for increased inbreeding, which may reduce long-term genetic diversity. To address this, strategies such as random mating within selection rounds or controlled hybridization can be implemented to maintain genetic diversity while maximizing genetic gain (Li et al., 2021). 7 Challenges and Countermeasures in Implementing Genomic Selection Implementing genomic selection (GS) in yam breeding programs is a complex process, requiring careful consideration of genetic, environmental, and logistical factors. While GS offers substantial potential for accelerating breeding cycles and improving trait selection accuracy, challenges such as marker density, sample size, and environmental interactions affect its efficacy. This section outlines these challenges and proposes countermeasures to enhance GS implementation in yam breeding.
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