Journal of Energy Bioscience 2025, Vol.16, No.1, 13-20 http://bioscipublisher.com/index.php/jeb 14 (Jackson et al., 2014; Mahadevaiah et al., 2021; Cursi et al., 2022). Sugarcane species have high polyploidy and rich genetic diversity, so the classification of sugarcane is complicated. Mahadevaiah et al. ’s study in 2021 showed that sugarcane hybrids (e.g. Saccharumspp. hybrids) were mostly formed by interspecific or intergeneric hybrids, and wild relatives also contributed. Xiong et al. ’s study in 2022 found that phylogenetic analysis divided several sugarcane species into different taxa, such as S. barberi and S. sinense, while modern sugarcane hybrids were mainly composed of S. officinarumandS. spontaneum. 2.2 Evolutionary origin and domestication history The studies of Yang et al. (2018), Pompidor et al. (2021) and Li et al. (2024) showed that the hybridization process of S. officinarum and S. spontaneum realized the development of modern sugarcane varieties, and sugarcane was used by people to produce sugar and bioethanol. Babu et al. ’s study in 2022 found that the domestication history of sugarcane is related to long-term selection for good traits such as high sucrose content and environmental adaptability (Figure 1). Yang et al. (2018) argued that genomic studies have found differences in the genetic composition of ancient and modern sugarcane hybrids, highlighting the importance of hybridization and artificial selection in the process of sugarcane domestication. Medeiros et al. (2020) and Xiong et al. (2022) found that genetic diversity and population structure analysis illustrated the evolutionary path and domestication process of sugarcane, and revealed the contribution of different sugarcane species to the genetic background of modern cultivated species. Figure 1 Timeline of sugarcane (Adopted from Babu et al., 2022) Image caption: a: Progenitor grass species; B: Evolutionary split of maize; C: Evolutionary split of sorghum; D: Genus Saccharum pre-domestication; E: Selection and domestication; F: Breeding and improvement; G: Transgenic development; H: Omics research; I: market release of transgenic sugarcane; J: sugarcane with better traits (Adopted from Babu et al., 2022) 2.3 Polyploidy and its implications Polyploidy is an important genetic feature of sugarcane, and it is also the main reason for the complexity and adaptability of sugarcane genome. Most of the modern sugarcane varieties have high polyploidy and complex nuclear genome background (Vilela et al., 2017; Zhou et al., 2022). Polyploidy increases the genetic variation of sugarcane and also provides the possibility for new trait combinations, which promotes the evolution and breeding of sugarcane. Vilela et al. (2017) showed that the multiploidy events of S. officinarum and S. spontaneum may have occurred independently, which promoted the diversification of sugarcane. Vilela et al. (2017) suggested that the presence of multiple haplotypes and the expression of homologous/homologous genes under purification selection indicated the functional importance of polyploidy in sugarcane adaptation and evolution. 3 Sugar Yield Traits and Their Genetic Background 3.1 Key traits related to sugar content Sugar yield of sugarcane is mainly determined by sucrose content, stem weight and stem yield per unit area, which are the core of many genetic studies. Ngaklunchon et al. (2023) and Rakesh et al. (2023) in the same year found that highly inherited traits such as sucrose content were suitable for selection at the early stage of breeding.
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