The complete chloroplast (cp) genomes of two Miscanthus species, M. sinensis and M. sacchariflorus, were sequenced and investigated for genes, genome size variation, and polymorphisms. There are 154 genes in both cp genomes, consisting of 122 coding genes, 40 tRNA genes, and 8 rRNA genes. The cp genome contains two inverted repeat (IR) regions, separated by large single copy (LSC) region and small single copy (SSC) region. 112bp indels in M. sinensis and 152bp in M. sacchariflorus were found mainly in LSC and SSC, which are responsible for 40 bp-difference in cp genome size in two species. Likewise, out of 94bp of SNPs, 88bp were found in LSC and SSC regions. Although gene number and sequence structure were quite well conserved, indel distribution and size were different in these two Miscanthus species.

More than 300 Miscanthus accessions as a potential bioenergy crop were collected in Korea and their morphological traits were investigated at various growth stages. Among morphological traits, stem growth habit, the presence of awn in spikelet, and autumn new shoot are the most important key traits enabling to cluster Miscanthus accessions into M. sinensis and M. sacchariflorus groups. Miscanthus sinensis has bunch stem growth habit and awn in spikelet, and produces autumn new shoot, while M. sacchariflorus has scattering stem growth habit with no awn in spikelet and does not produce autumn new shoot. Interestingly, we found several Miscanthus accessions showing intermediate morphological traits. 7 M. sinensis accessions showed morphological traits similar to M. sacchariflorus and 17 M. sacchariflorus accessions showed morphological traits similar to M. sinensis. Flow cytometry and chromosome counting finally revealed 5 Miscanthus hybrids, suggesting that they are resulted from natural hybridization between M. sinensis and M. sacchariflorus. Therefore, these Miscanthus hybrids can be used to understand genetic recombination between these two Miscanthus species and our understanding may support future efforts for breeding new Miscanthus variety with high biomass productivity and environmental adaptability.