Jiayong Liu

Sugarcane (Saccharum spp. L.) is a globally vital sugar and energy crop whose genetic improvement has been constrained by its complex polyploid–allopolyploid genome. To address this limitation, we developed a practical, high-throughput single-nucleotide polymorphism (SNP) genotyping system. Using specific-locus amplified fragment sequencing (SLAF-seq) on 107 diverse accessions, we identified 2,420,550 high-quality SNPs anchored to the Saccharum officinarum LA-Purple genome. Stringent filtering yielded 55,750 SNPs for population analysis, which revealed three distinct genetic groups consistent with breeding history and adaptation. From these resources, 329 SNPs were converted into PCR-based ligase detection reaction (PCR-LDR) markers, resulting in a validated panel of 177 highly reliable SNPs (151 core and 26 extended) organized into an efficient multiplex typing system. The panel exhibited exceptional discriminatory power, successfully distinguishing all 303 tested sugarcane varieties and clearly resolving 186 individuals from three segregated hybrid populations. Compared to existing SSR and SNaPshot platforms, this SNP system offers superior experimental reproducibility, enhanced varietal clustering, and broader genome coverage. This work provides a robust, efficient genotyping tool to advance sugarcane variety identification, germplasm management, pedigree analysis, and marker-assisted breeding, with potential applicability to other complex polyploid crops.

Sugarcane (Saccharum spp.), a vital economic crop, suffers significant yield losses from drought. This study elucidates the genetic regulation of lignin biosynthesis—a key drought-resistance mechanism—by analyzing three contrasting accessions: drought-sensitive Saccharum officinarum (Badila), drought-resistant hybrid (XTT22), and drought-tolerant wild Saccharum spontaneum (SES-208) under progressive drought (7–21 days). Physiological analyses revealed pronounced lignin accumulation in XTT22 roots/leaves, driven by elevated coniferyl/sinapyl alcohol substrates, while Badila showed minimal deposition. Genomic characterization of cinnamyl/sinapyl alcohol dehydrogenase (CAD/SAD) families across six sugarcane genomes identified 322 genes phylogenetically clustered into three clades. Class I members (CAD1, CAD5, etc.) were critical for lignin biosynthesis, with tandem/segmental duplications driving family expansion and promoters enriched in stress-responsive cis-elements (ABA, MeJA, light). Transcriptomics and qRT-PCR confirmed strong correlations between Class I CAD expression, lignin content, and drought tolerance. These findings establish CAD Class I genes as novel molecular targets for enhancing drought resilience in sugarcane breeding programs.

The ratooning capacity of sugarcane cultivars represents a crucial agronomic trait that significantly influences the sustainability of crop yields. This study elucidates the physiological and molecular mechanisms underlying the sugarcane ratooning ability observed in ratoon-competent GuiTang 29 (GT29) and ratoon-deficient Badila cultivars following stem excision. Through integrated hormonal profiling and transcriptome analysis, we identified significant differences in hormone levels and gene expression patterns. The quantification of 15 endogenous hormones via HPLC revealed marked reductions in zeatin (ZA) and zeatin riboside (ZR) in both cultivars. Additionally, GT29 exhibited notable reductions in gibberellins (GA3 and GA5) and strigolactone (5-DS) post-stem-excision, while Badila displayed stable or distinct hormonal changes. Additionally, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that hormone signal transduction, MAPK signaling pathways, phenylpropanoid biosynthesis, flavonoid biosynthesis, and other metabolic pathways were significantly enriched in both GT29 and Badila, with a particularly higher enrichment of plant hormone signal transduction in GT29. Furthermore, several differentially expressed genes (DEGs) had different expression patterns between GT29 and Badila, including the cytokinin receptor B-ARR and transcription factor A-ARR, gibberellin pathway components GID1 and DELLA, and AUX/IAA and SAUR in the auxin pathway. The real-time quantitative PCR (qRT-PCR) validation of 12 DEGs corroborated the RNA-seq data, further supporting the reliability of the transcriptomic analysis. This study delineates a clear molecular framework distinguishing ratoon competence, offers novel insights into the molecular basis of perennial regeneration and provides reliable candidate genes for functional marker development in sugarcane breeding.

Saccharum spontaneum serves as an essential genetic resource for sugarcane improvement. Traditional breeding methods, characterized by slow selection and limited germplasm exploitation, often lead to suboptimal progeny performance. In this study, we revised the utilization strategy by initially hybridizing several S. spontaneum clones, followed by intercrossing their F1 progeny to establish a heterogeneous ‘polymeric’ population, which was then subjected to ‘nobilization’. A natural Saccharum spontaneum (S0) plant was used as the parent to create a hybrid (S1) containing two S. spontaneum bloodlines. The agronomic traits of S1 were compared, leading to the identification of three superior hybrids. These hybrids were then crossed in a complete diallel design, resulting in six crosses. Significant genetic variation was observed for the agronomic traits. Compared with S0, the plant height in S1 increased by 31.5%, and by 32.22% in S2. The stem diameter in S1 increased by 38.71%, and by 51.61% in S2. The single stem weight increased by 125% in S1 and 150% in S2. Other yield traits also showed varying degrees of improvement. A correlation analysis indicated that the plant height, stalk diameter, single stalk weight, and leaf width were significantly positively correlated with yield, and the leaf width with brix. There was no significant correlation between the millable stalks and yield. This study successfully developed a novel S. spontaneum hybrid with significantly improved agronomic traits, enhancing the genetic foundation of S. spontaneum germplasm for nobilization breeding programs. These findings provide a valuable germplasm base for developing high-performance sugarcane varieties, improving the utilization of S. spontaneum.

Interspecific hybridization serves as a crucial strategy for innovating sugarcane germplasms. Currently, nearly all modern sugarcane varieties that incorporate genetic material are derived from Saccharum spontaneum. The number of chromosomes in S. spontaneum ranges from 40 to 128, contributing significantly to the diversity of its genetic resources. However, the genetic mechanisms driving chromosome number variation in S. spontaneum remain to be fully elucidated. Here, oligonucleotide fluorescence in situ hybridization (Oligo-FISH) was conducted to identify individual chromosomes and explore chromosome transmission during the intraspecific hybridization of S. spontaneum. The results indicate that from the progenies generated from S. spontaneum Yunnan2017-22 (2n = 8x = 64) and Yunnan82-1 (2n = 8x = 64) emerged two distinct karyotypes, 2n = 12x = 96 (A1) and 2n = 8x = 64 (A2, A33-1, A18). This implies that the chromosome inheritances were 2n + n and n + n in the progenies. However, self-pollinated samples of A1 (2n = 12x = 96) produced normal offspring C1 (2n = 94) and C2 (2n = 96). The 2n + n inheritance pattern did not continue. In another cross, the progenies derived from S. spontaneum Yunnan2017-41 (2n = 8x = 64) and Yunnan8 (2n = 10x = 80) carried a karyotype of 2n = 9x = 72, with n + n inheritance mode. These findings highlight the existence of two chromosome inheritance modes, 2n + n and n + n, in the context of the intraspecific hybridization of S. spontaneum. Additionally, hybridization between different ploidy S. spontaneum was also accompanied by chromosomal translocations (A1, A2, A18, A18) and loss (A2, A33-1, AA-4, and C2) that further resulted in the complexity of the S. spontaneum genome. Together, these findings highlight diverse chromosome inheritance in S. spontaneum hybridization, and provide a theoretical foundation for the further utilization of S. spontaneum germplasm in sugarcane breeding.