Miscanthus spp. are energy plants and excellent candidates for phytoremediation approaches of metal(loid)s-contaminated soils, especially when combined with plant growth-promoting bacteria. Forty-one bacterial strains were isolated from the rhizosphere soils and roots tissue of five dominant plants (Artemisia argyi Levl., Gladiolus gandavensis Vaniot Houtt, Boehmeria nivea L., Veronica didyma Tenore, and Miscanthus floridulus Lab.) colonizing a cadmium (Cd)-contaminated mining area (Huayuan, Hunan, China). We subsequently tested their plant growth-promoting (PGP) traits (e.g., production of indole-3-acetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase) and Cd tolerance. Among bacteria, two strains, Klebsiella michiganensis TS8 and Lelliottia jeotgali MR2, presented higher Cd tolerance and showed the best results regarding in vitro growth-promoting traits. In the subsequent pot experiments using soil spiked with 10 mg Cd·kg⁻¹, we investigated the effects of TS8 and MR2 strains on soil Cd phytoremediation when combined with M. floridulus (Lab.). After sixty days of planting M. floridulus (Lab.), we found that TS8 increased plant height by 39.9%, dry weight of leaves by 99.1%, and the total Cd in the rhizosphere soil was reduced by 49.2%. Although MR2 had no significant effects on the efficiency of phytoremediation, it significantly enhanced the Cd translocation from the root to the aboveground tissues (translocation factor > 1). The combination of K. michiganensis TS8 and M. floridulus (Lab.) may be an effective method to remediate Cd-contaminated soils, while the inoculation of L. jeotgali MR2 may be used to enhance the phytoextraction potential of M. floridulus.

Background: Miscanthus, which is a leading dedicated-energy grass in Europe and in parts of Asia, is expected to play a key role in the development of the future bioeconomy. However, due to its complex genetic background, it is difficult to investigate phylogenetic relationships in this genus. Here, we investigated 50 Miscanthus germplasms: 1 female parent (M. lutarioriparius), 30 candidate male parents (M. lutarioriparius, M. sinensis, and M. sacchariflorus), and 19 offspring. We used high-throughput Specific-Locus Amplified Fragment sequencing (SLAF-seq) to identify informative single nucleotide polymorphisms (SNPs) in all germplasms. Results: We identified 257,889 SLAF tags, of which 87,162 were polymorphic. Each tag was 264–364 bp long. The obtained 724,773 population SNPs were used to investigate genetic relationships within three species of Miscanthus. We constructed a phylogenetic tree of the 50 germplasms using the obtained SNPs and grouped them into two clades: one clade comprised of M. sinensis alone and the other one included the offspring, M. lutarioriparius, and M. sacchariflorus. Genetic cluster analysis had revealed that M. lutarioriparius germplasm C3 was the most likely male parent of the offspring. Conclusions: As a high-throughput sequencing method, SLAF-seq can be used to identify informative SNPs in Miscanthus germplasms and to rapidly characterize genetic relationships within this genus. Our results will support the development of breeding programs with the focus on utilizing Miscanthus cultivars with elite biomass- or fiber-production potential for the developing bioeconomy.

In this study, polyploid Miscanthus lutarioriparius (PML) was introduced as a new sustainable and scalable source for cellulose nanocrystal (CNC). The agronomic traits of PML were significantly different from Miscanthus × giganteus (MG), but their chemical components and physical features were similar. Notably, a remarkable co-extraction of hemicellulose, lignin and ash and non-crystalline cellulose was observed during crude cellulose isolation from PML than it from MG by modified alkaline peroxide pretreatment. In addition, subjecting crude cellulose of PML and MG biomass to sulfuric acid hydrolysis provided high-quality CNC. The analysis of particle size distribution, zeta potential, crystalline index, the degree of polymerization, SEM and yield potential suggested that the CNC extracted from PML showed higher stability, processability and productivity than that from MG. Therefore, it provides a new theoretical basis for the applications of CNC prepared by PML and MG. The results also revealed potential genetic approaches for Miscanthus spp. to enhance biomass and CNC yield.

Cultivating the dedicated biomass crop Miscanthus on marginal land is a sustainable means of avoiding competition with food crops for arable land. A large proportion of global marginal land is saline–alkaline; however, little is known about the performance of Miscanthus in saline-alkaline soil. In this study, Miscanthus × giganteus and ten other Miscanthus hybrids grown in the Yellow River Delta were exposed to low and saline–alkaline soils during the 2016–2018 growing season to evaluate the agronomic traits, biomass quality and the potential productive index of eleven Miscanthus genotypes. Plant biomass, plant height, and tiller number significantly decreased in high saline–alkaline soil. In particular, the average plant biomass of ten Miscanthus hybrids in low saline–alkaline soil in 2017 and 2018 were 0.21 and 2.25 kg per plant, respectively, and in high saline-alkaline soil were 0.13 and 0.65 kg per plant, respectively. Cell wall, cellulose, and nitrogen content of all genotypes significantly decreased in high saline–alkaline soil, while hemicellulose, ash, sodium, potassium, magnesium, and calcium content significantly increased. However, high saline–alkaline soil had no observable impact on lignin content of Miscanthus biomass. The effect of high saline-alkaline on biomass quality parameters could provide important information for the application of Miscanthus biomass in saline-alkaline soil. The selected genotypes (A5) could be considered as breeding materials in saline-alkaline soil.

The pretreatment of lignocellulosic biomass such as Miscanthus grown on marginal agricultural land is very challenging and requires severe conditions to fractionate cell wall polymers for further valorization. The current study aimed to determine organic acid-based mild conditions to pretreat contrasting lignocellulosic Miscanthus genotypes for the efficient fractionation of cell wall components, with special focus on hemicellulose extraction. In doing so, five Miscanthus genotypes were subjected to four different acid treatments (sulfuric acid, oxalic acid, malonic acid, and citric acid) in a vertical high-pressure steam sterilizer. The results demonstrated that, among the organic acids, oxalic acid was identified as the most effective pretreatment solvent for hemicellulose separation, whereas citric acid yielded the highest amount of galacturonic acid, varying from 15 to 17 mg mL⁻¹ across genotypes. One best performing genotype was selected for the enzymatic hydrolysis. Overall, M. floridulus genotypes exhibited the optimal quality traits for efficient bioconversion with second best in terms of ethanol production potential.

Miscanthus spp. has been regarded as a promising industrial plant for the sustainable production of bio-based materials. To assess its potential for microcrystalline cellulose (MCC) and cellulose nanocrystals (CNCs) production, 50 representative clones of M. sinensis and M. floridulus were selected from a nationwide collection showcasing the extensive diversity of germplasm resources. Descriptive analysis indicates that the dry biomass weight of M. floridulus is advantageous whereas M. sinensis demonstrates higher MCC and CNCs yields as well as a smaller CNCs particle size. Correlation analyses indicated that MCC yield is solely influenced by the cellulose content whereas the yield of CNCs is affected by both the cellulose content and CrI. Comparative analyses of the chemical composition, physical features (degree of polymerization, crystalline index, particle size distribution and zeta potential), and scanning electron microscopy indicated that the MCC and CNCs extracted from M. sinensis and M. floridulus exhibited remarkable stability and quality. Additionally, the CNCs derived from M. sinensis and M. floridulus exhibited a distinctive ball-shaped structure. Notably, machine learning has demonstrated its efficacy and effectiveness in the high-throughput screening of large populations of Miscanthus spp. for predicting the yield of MCC and CNCs. Our results have also laid the theoretical foundation for the exploration, cultivation, and genetic breeding of M. sinensis and M. floridulus germplasm resources with the purpose of MCC and CNCs preparation.