Lignocellulosic biomass may play a major role in the production of biofuels, bioplastics, sugar, paper, and various other industrial products. In addition, it is a key trait in plants due to its contribution to lodging resistance. Fiber also shows a significant negative correlation with most yield traits and all sugar traits. As the most harvested crop globally by tonnage, sugarcane is an important resource for both sugar and bioenergy production. In this study, a panel of sugarcane clones was utilized to investigate the fiber content. This panel included 17 core parental lines derived from 11 countries involved in sugarcane cultivation and breeding. It represented the genetic base of commercial sugarcane breeding programs in China and other countries. The objective of this research was to identify molecular markers and candidate genes associated with fiber content in sugarcane using genome-wide association studies (GWASs). By integrating 5,964,084 high-quality single-nucleotide polymorphisms (SNPs) with phenotypic data collected across five different environments, a total of 69 SNPs spanning 41 quantitative trait loci (QTLs) were identified. Based on functional annotations and genomic positions, these QTLs contained 52 candidate genes. These candidate genes encoded the ultraviolet-B receptor (UVR8), leucine-rich repeat receptor-like kinases (LRR-RLKs), serine/threonine kinases (STKs), cellulose synthase (CESA), vegetative cell wall protein glycoproteins1 (gp1), F-box protein, MYB transcription factor, and so on. These genes could directly or indirectly influence the fiber content in sugarcane. Furthermore, according to previous studies, among these candidate genes, five located in four QTL regions were proposed to be the most critical. They included Sspon.02G0041160-2C, encoding CESA; Sspon.03G0039010-1C and Sspon.03G0039030-1C, both encoding gp1; Sspon.06G0023090-1B, encoding an F-box protein; and Sspon.07G0019440-2C, encoding a MYB transcription factor. The genetic basis of the fiber content was explored using elite breeding lines and their derivatives from the Chinese sugarcane breeding program. These candidate genes represent promising targets for future functional studies and may contribute to the development of different types of sugarcane varieties with correspondingly suitable fiber content through marker-assisted selection.

Photosynthesis is the ultimate source of energy for crop productivity, and leaf morphology as well as chlorophyll content are traditional, indirectly related traits of photosynthesis. However, the genetic basis of these traits remains unexplored in sugarcane. In this study, we conducted genome-wide association studies (GWAS) to identify loci controlling nine photosynthesis-related traits, including four leaf morphological traits (leaf length, leaf width, leaf ratio, and leaf area) and five chlorophyll-related traits (chlorophyll a, chlorophyll b, chlorophyll a/b ratio, total chlorophyll, and SPAD value). The analysis was performed using whole-genome resequencing data from 219 elite, globally diverse sugarcane materials evaluated at two locations across two years (four environments). Based on 5,964,084 high-quality single nucleotide polymorphisms (SNPs), we identified 308 GWAS-significant SNPs (p ≤ 1.5 × 10⁻⁶) that were consistently detected in two or more environments, defining 97 GWAS-associated intervals across 30 chromosomes. Within these intervals, 98 putative genes were predicted, of which 20 genes in 16 intervals were potentially associated with leaf photosynthesis based on functional annotation and literature mining. These candidates are primarily involved in pathways related to ADP-ribosylation factors, ATP-dependent Clp protease proteolytic subunits, protein kinases, F-box proteins, MYB and WRKY transcription factors, UVR8, pentatricopeptide repeat-containing (PPR) proteins, Aux/IAA proteins, monogalactosyldiacylglycerol (MGDG) synthase, Orange (OR) proteins, PsbP domain-containing (PPD) proteins, and chloroplast stem-loop binding proteins of 41 kDa b (CSP41b). Ten genes were prioritized for future functional validation. Notably, these photosynthesis-related structural and pigment traits represent a different regulatory layer from direct gas exchange parameters (e.g., net photosynthetic rate), and their associations with actual photosynthetic efficiency require further validation. Nevertheless, this study provides novel candidate genes and molecular markers to assist marker-assisted breeding aimed at improving the photosynthetic structure and light-harvesting capacity of sugarcane.