International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 230 taste. In addition to moderate fiber content, juicy varieties often have large stem pith cells, well-developed vacuoles, and high water content. Although the cell walls of this type of variety are not necessarily particularly thin, due to the fullness of juice, the cells are easily broken and release juice when chewed, and the fiber bundles are also dispersed by the juice, so it feels "more water and less residue". In contrast, the anatomical structure of coarse-fiber varieties shows that their vascular sheaths and thick-walled tissues are well developed, the cell walls of xylem fibers are thick, lignin is deposited a lot, the intercellular spaces are small, and the water content is low (Wang et al., 2020). When chewing this type of sugarcane, the tough fibers are not easily cut by the teeth, and the juice is not easily squeezed out completely. The residue clumps into filaments and has a poor taste. Therefore, the formation of fresh sugarcane with different texture types is directly related to the quantity and quality of cell walls. In terms of molecular mechanism, it is speculated that the expression of genes in the cell wall synthesis pathway of tender and crisp sugarcane is weakened, while the expression of wall relaxation enzymes such as swelling protein and XTH may be relatively high, resulting in relatively thin and soft cell walls; the coarse fiber type is the opposite, and the genes related to lignin synthesis and secondary wall development may be highly expressed, making the cell wall thicker and harder. These inferences need to be verified by transcriptome and metabolome experiments. Existing studies such as Chen et al. (2022) reported that sugarcane generally has "low fiber content and sweet and delicious sugarcane juice", suggesting that high-quality fresh sugarcane tends to accumulate more sugar and water in metabolism and allocate less carbon to secondary wall substances. These characteristics are closely related to specific gene expression regulation and are the targets for the next step of quality improvement. 6.3 Transcriptomic comparison of elite vs. traditional germplasm In order to understand the quality formation mechanism of fresh sugarcane from a global perspective, researchers have begun to use multi-omics methods to compare the differences between high-quality varieties and ordinary varieties and wild species. In particular, transcriptome sequencing can reveal the full picture of gene expression of different genotypes at key developmental stages. For example, a study compared the transcriptomes of high-sugar and low-fiber sugarcane varieties with those of a common sugarcane variety and found significant expression differences in hundreds of genes between the two, involving multiple functional categories such as carbohydrate synthesis and degradation, cell wall metabolism, hormone signaling, and transcriptional regulation (Li et al., 2023). Genes specifically upregulated in high-quality sugarcane varieties include some sucrose transport and synthesis enzymes (such as SWEET4, SPS genes) and cell wall modification enzymes (such as EXP, XTH genes), which are consistent with their high-sugar and soft phenotypes; while a group of genes highly expressed in common varieties are related to xylem development and defense response (such as PAL, DIR genes), which may explain the characteristics of their harder fibers but stronger stress resistance. Similarly, similar trends have been observed between wild relatives and cultivated species of sugarcane. About 80% of the genome of modern sugarcane varieties is derived from high-sugar cultivated species (tropical sugarcane), 10%-20% is derived from high-fiber wild species (cut-hand dense), and a small part is a recombination of the two. This genomic hybridization has resulted in modern varieties that have both high sugar content and toughness. However, comparisons of extreme materials, such as the analysis of hybrid offspring between the wild species of Scutellaria baicalensis and the noble species, found that the sucrose content and fiber content of the stems were genetically negatively correlated. Some alleles from wild species tend to increase fiber yield but reduce sugar content, while alleles from cultivated species are the opposite. The average hammer of the wild species of Scutellaria baicalensis was only 8.75°Bx, and the hammer of the F1 offspring hybridized with cultivated sugarcane increased to 13.75°Bx, increased to 18.2°Bx in the first backcross generation, and reached 20.2°Bx in the third backcross generation. This shows that the sweetness of sugarcane can be greatly improved by aggregating the high-sugar genes of cultivated species and removing the high-fiber genes of wild species through several generations of backcrossing (Deng et al., 2019). The differences in gene expression behind this are also obvious: the expression levels of some key sugar accumulation genes such as SPS and SuSy in the cut hand secret are much lower than those in the cultivated species, while the expression of genes related to lignin synthesis is
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