The trehalose-6-phosphate synthase (TPS) gene family plays important roles in conferring plant stress resistance, but a comprehensive analysis of the gene family is lacking for sugarcane (Saccharum spp. hybrids). The objective of this study is to document functional classification, evolutionary characterization, and expression profiling of sugarcane TPS gene (ScTPS) family. Nine putative ScTPS genes were identified and assigned to two distinct classes based on gene structure and phylogeny. Phylogenetic analysis showed that 31 TPS genes from Arabidopsis, rice and sugarcane could be divided into five distinct clades, suggesting that there were at least five orthologous groups in monocot and dicot plants. Evolution analysis of TPS genes revealed that TPS family members appeared to have undergone strong negative selection. The strength of the selective pressure differed in most clades, especially Class I TPS genes, experienced significantly stronger negative selection pressure than Class II TPS genes. There were also cis-regulatory elements related to phytohormones and abiotic stresses. Additionally, ScTPS genes were found to exhibit divergent expression in response to simulated drought, salinity, and ABA stresses. Since ScTPS genes function in sugarcane adaptation to environmental stimuli, it might be used as a molecular marker in screening sugarcane germplasm for increased stress resistance.

In China, sugarcane (Saccharum spp.) hybrid cross-breeding began in 1953; approximately 70 years since then, >100 commercial sugarcane varieties have been created. In this study, 88 commercial varieties bred in China between 1953 and 2010 and 12 original foundational varieties were planted to investigate the effect of improving sugarcane varieties in China. Considering 20 years as a time node, the commercial varieties were classified into four improved generations. Retrospective analysis showed significant improvements in sucrose and other technological characteristics of commercial sugarcane varieties. The adoption of improved varieties over generations has continuously increased sugarcane’s sucrose, juice sugar, and gravity purity, and the difference was significant between Gen1 and Gen3, and between Gen2 and Gen4. Gen4 showed 2.06%, 2.35%, and 3.69% higher sugarcane sucrose (p < 0.01), juice sugar (p < 0.01), and purity (p < 0.05), respectively, and 1.13% lower sugarcane fiber (p < 0.01) than Gen1, the original foundational hybrid varieties. The development of new varieties has improved the technological characteristics of Chinese sugarcane. Sugarcane sucrose, juice sugar, and purity showed an increasing trend. Sugarcane fiber content did not significantly change with the development of new varieties but declined in comparison with the original foundational hybrid varieties.

Sugarcane (Saccharum spp.) breeding in China has a history of nearly 70 years. Yunnan province represents the second largest sugarcane planting area in China; therefore, by studying the evolution of sugarcane varieties in this region, it is possible to gain an understanding of the process of improvement since the foundation of sugarcane hybrid breeding. In this study, we compared the main industrial and agronomical characteristics of 107 sugarcane varieties, developed between 1952 and 2020, and discussed the reasons for replacement and exchange. Overall, significant differences were observed (p < 0.01), highlighting notable improvements, especially in terms of yield; however, disease incidence remains a serious issue and the fundamental reason for variety replacement. Meanwhile, analysis of parent traceability revealed that the main varieties cultivated at present have a similar parental relationship based around CP, F, and YC series germplasms. Taken together, these findings suggest that disease-resistant breeding should be strengthened, and susceptible varieties eliminated, while making full use of existing varieties as core parents.

TGA transcription factor (TF) family genes play a major role in the regulation of plant growth and development as well as in the defense against pathogen attack. Little is known about the TGA family genes and their functions in sugarcane. Here, a total of 16 TGA members were identified in the sugarcane genome by bioinformatic approaches. All members exhibited similar conserved motifs and contained a bZIP domain and a DOG1 domain, except for ShTGA15/16. Phylogenetic analysis demonstrated that 16 ShTGA family genes could be divided into eight clades, and evolved differently from Arabidopsis TGAs. All ShTGA family genes suffered a purifying selection during evolution. A wide range of cis-regulatory elements were found in the promoter of ShTGA genes including hormone regulatory elements, adversity response elements, light responsive elements, and growth and development regulatory elements. Most ShTGA expressions were increased in bud growth and developmental processes except for ShTGA10/11. It is worth noting that the expression of ShTGA13 was decreased after sugarcane was infected with Sporisorium scitamineum, and it was highly expressed in the resistant variety compared to the susceptible variety. Adding IAA, GA₃ and SA restored the expression of ShTGA13, suggesting an association with plant hormone regulatory pathways. Our study provides a framework for further functional studies of important ShTGA genes in development and stress response, and uncovered a previously unrecognized role of ShTGA13 in regulating resistance against S. scitamineum.

Sugarcane is a complex polyploid aneuploid cash crop, and transgenic varieties are important for molecular genetic and traditional breeding approaches. Herein, the sugarcane variety ROC22 served as the receptor, the Bar gene served as a screening marker, and positive and negative fragments of the ScD27.2 gene, upstream of strigolactones (SLs) biosynthesis genes driven by the 35S promoter, were introduced by Agrobacterium tumefaciens-mediated transformation. Regenerated plants were obtained by co-culture, screening culture, and differentiation induction, and 27 sense and antisense ScD27.2 transgenic seedlings were obtained by herbicide screening. PCR detection and 1% Basta (Glufosinate) application on leaves revealed Bar in all lines, with all testing positive for herbicide application and 23 containing the target gene (positive resistance screening rate = 87.5%). q-PCR and phenotypic analyses showed that ScD27.2 expression, plant height, tiller number, root length, stem diameter, and fresh weight were decreased in transgenic (ScD27.2R-9) compared with non-transgenic (NT and ScD27.2F-2) lines. ScD27.2 expression was downregulated, and growth potential was inhibited. Under 20% PEG treatment, malondialdehyde (MDA) content in ScD27.2R-9 was higher than in NT, while proline content was lower. Under drought stress, ScD27.2 expression, MDA levels, and proline content in ScD27.2F-2 and NT were higher than in non-treated controls, ScD27.2 expression increased with time, and MDA and proline levels also increased. ScD27.2 expression in ScD27.2R-9 decreased under 20% PEG treatment, MDA and proline increased (but not to NT levels), and growth was lower than NT. The 20% PEG treatment also increased the levels of (±)-2′-epi-5-deoxystrigol and (+)-abscisic acid in the rooting culture media of ScD27.2F-2, ScD27.2R-9, and NT lines, but the levels of (+)-abscisic acid content in ScD27.2R-9 was lower than in NT. Thus, interfering with ScD27.2 expression decreased resistance to 20% PEG treatment. ScD27.2 encodes a β-carotene isomerase involved in SLs biosynthesis that might function in sugarcane resistance to drought stress. It explains the role of SLs in sugarcane growth and development and responses to drought stress.