Discovery of Natural Interspecific Hybrids Between Miscanthus Sacchariflorus and Miscanthus Sinensis in Southern Japan: Morphological Characterization, Genetic Structure, and Origin

Natural Miscanthus grasses are useful for improving biomass production. We found a population of putative triploid interspecific hybrids between Miscanthus sacchariflorus and Miscanthus sinensis in southern Kyushu, Japan. This study aims to investigate its morphological variation, genetic structure, and origin. Miscanthus plants were collected from 114 points, mainly beside a river along a distance of 2.8 km in the Tashiro–Fumoto area. They resembled M. sacchariflorus but showed morphology intermediate between the two species. They had a nuclear DNA content corresponding to that of a hybrid between tetraploid M. sacchariflorus and diploid M. sinensis, and had species-specific alleles from both species revealed by DNA marker analysis. This indicates that the plants are triploid hybrids between M. sacchariflorus and M. sinensis. Genotyping using simple sequence repeat markers revealed only four genotypes among the hybrid population, of which two accounted for most plants. The genotypes showed mostly discrete geographical distributions. The two major genotypes showed contrasting phenotypes in pollen viability and in frequency of awns in florets. Some seeds collected from the population germinated and the seedlings showed a wide range of nuclear DNA content from diploid to tetraploid. In this area, many M. sinensis plants also grew, but we could not find M. sacchariflorus. The hybrid Miscanthus might be selected due to its improved adaptability introduced from M. sinensis. Furthermore, genetic and phenotypic characterization suggests the polyphyletic origin and clonal propagation of this population. Such partially fertile hybrids could be interesting for the improvement of Miscanthus as a biomass crop.