Phytoremediation using Miscanthus is a valuable technique for the restoration of saline‐alkaline soil, but the potential is not quantified. To assess this potential, a 5 years field experiment was conducted on saline‐alkaline soils with three genotypes of Miscanthus and an unplanted control. The bulk soil (0–20‐cm depth) physicochemical properties were measured annually from 2015 to 2018, while the bacterial and fungal community structures of the rhizosphere soil were investigated by high‐throughput sequencing after 5 years under Miscanthus (2018). The results showed that Miscanthus cultivation on saline‐alkaline soil reduced soil salinization and improved soil fertility on this site. Specifically, compared with the blank control, the five‐years Miscanthus cultivation (mean of three different genotypes pooled) decreased the soil pH by 0.33 units (8.78–8.45) and electrical conductivity by 23.4 μS/cm (226.7–203.3 μS/cm), as well as increasing soil organic matter content from 18.9 to 34.9 g/kg and total potassium content from 15.2 to 18.0 g/kg. In addition, the soil improvement was more pronounced with a longer duration of growth. Miscanthus remediates saline‐alkaline soils by altering the microbial community compositional abundance rather than its diversity. The improvement is due to enrichment of beneficial bacteria leading to soil desalinization (e.g., by Gemmatimonadaceae), litter decomposition (e.g., by Chitinophagaceae), plant growth promotion (e.g., by Micrococcaceae), and the reduction of harmful fungi (e.g., Pleosporales and Chitinophagaceae). Soil pH, electrical conductivity, organic matter, and total potassium were the main physicochemical properties affecting bacterial and fungal communities. Our results quantify the soil improvement potential of Miscanthus and clarify the underlying microbial mechanisms, laying a solid foundation for further implementation of saline‐alkaline soil phytoremediation using Miscanthus. In the future, more extensive multi‐location trials are required to assess if these improvements are seen across a wide diversity of environments.

Miscanthus, a perennial rhizomatous C4 grass, has emerged as a promising lignocellulosic crop. To avoid competition with food crops, marginal lands especially saline‐alkaline soil are being recommended to grow Miscanthus across China. . However, the challenges such as high cost and low reproduction coefficient associated with the propagation methods are impeding its large scale plantation in saline‐alkaline soil. In this study, a ‘two‐steps’ propagation method was designed, which was comprised of two phases: 1) seedling cultivation; 2) seedling strengthening. The parameters (substrate composition and plug size) for this method were determined. The optimal substrate composition of the seedling bed for M. sinensis, M. lutarioirparius and their interspecific hybrids were peat and perlite at a ratio of 3:2, 3:1 and 3:3 by volume, respectively. The seedlings were transplanted into the plugs to deliver robust plantlets. The most appropriate plug size for M. sinensis, M. lutarioirparius and their interspecific hybrids was 50 plugs (50cm³/plug), 72 plugs (40cm³/plug) and 72 plugs (40cm³/plug), respectively. Three propagation methods i.e. direct sowing of seeds, rhizomes plantation and ‘two‐steps’ seed‐derived plugs for M. lutarioriparius were compared in saline‐alkaline soil over three years (2014, 2015 and 2016). The establishment rate of the seeds directly planted was poor (zero). The performance (e.g., biomass yield) of the plants derived from the ‘two‐steps’ seed‐derived plugs was better than that of the plants derived from rhizomes directly planted. Therefore, the ‘two‐steps’ seed‐derived plugs can be regarded as an effective propagation method to upscale Miscanthus cultivation in saline‐alkaline soil.

The genus Miscanthus is a promising lignocellulosic feedstock crop for the production of bioenergy. Miscanthus is drawing attention because it can be grown on marginal land and avoid competition with food crops. Therefore, as measures of performance, biomass yield and quality of two parent species (Miscanthus sinensis and Miscanthus lutarioriparius) and 15 of their interspecific hybrids were evaluated in a saline–alkaline soil of the Yellow River delta in China. Ethanol and biogas production potentials were also estimated. A field trial with a randomised block design with five replicates of each genotype was conducted in 2014. Biomass yield, plant height, tiller number, stem diameter, and tiller mass of each parent and hybrid were measured at the end of the growing season in 2015, 2016, and 2017. Quality traits, including cellulose, hemicellulose, lignin and ash contents, were measured. There was large genotype variation in biomass yield and in most of the biometric parameters, and cellulose (range: 0.33 to 0.45 g/g), hemicellulose (0.32 to 0.43 g/g), lignin (0.07–0.13 g/g) and ash (0.02–0.06 g/g) contents were significantly different among the hybrids. The ash content of all hybrids was significantly lower than that of M. sinensis. The two‐year (2016 and 2017) average biomass yield of the 15 hybrids ranged from 9.87 to 23.11 t/ha, which was significantly higher than that of either parent (M. sinensis: 1.20 t/ha; M. lutarioriparius: 3.87 t/ha). Two hybrids, SL8 and SL15, were identified as potential genotypes suitable for the saline–alkaline soils of the Yellow River delta. These results demonstrate that interspecific hybridisation is crucial to improve Miscanthus biomass yield and quality under marginal conditions.

Core collections can act as a genetic germplasm resource for biologists and breeders. Thirty-seven phenotypic traits from 471 Miscanthus accessions in China were used to design 203 sampling schemes to screen the genetic variations in different sampling strategies. The sampling was analyzed using the unweighted pair group method with arithmetic mean (UPGMA) and the Euclidean distance (Euclid). Several parameters including the variance of phenotypic value (VPV), Shannon–Weaver diversity index (H), coefficient of variation (CV), variance of phenotypic frequency (VPF), ratio of phenotype retained (RPR), the mean difference percentage (MD%) and the variance difference percentage of traits (VD%), the range coincidence rate (CR%) and the variable rate of quantitative traits (VR%) were used to evaluate the level of representation of the primary core collections developed by the different sampling schemes. Based on the optimal sampling strategies of prior selecting accessions, a primary core collection was constructed that maintained > 99.5% of the VPV and a CR% of 100%. This study indicates that the optimal sampling scheme consisted of prior and deviation sampling methods (PD) combined with a logarithmic proportional sampling strategy (LG) of 37.4% of the actual sampling ratio. Sampling before clustering can improve several parameters including the H, CV, RPR, VPF, and CR%. Sampling strategies including the genetic diversity index (G), logarithmic proportional (LG) and the square root proportional strategy (SG) can improve the H, whilst the constant strategy (C) can improve the RPR and VPF when the sampling scale was >30%. Furthermore, the proportional strategy (P) can improve the VPV.