Naturally occurring triploid hybrids between Miscanthus sacchariflorus and M. sinensis in Southern Japan, show phenotypic variation in agronomic and morphological traits

Abstract

Miscanthus × giganteus, a triploid hybrid between tetraploid M. sacchariflorus and diploid M. sinensis, is considered to be a promising biomass crop for producing renewable bioenergy in temperate regions. However, because most cultivars of the hybrid have been derived from a single clone through vegetative propagation, genetic resources with diverse phenotypes are required to allow adaptation to changing environments and resistance to pests and diseases. The present study aimed to identify novel natural hybrids between M. sacchariflorus and M. sinensis and to assess their natural variation in agronomic and morphological traits. We have identified 51 Miscanthus plants with nuclear DNA content of triploid Miscanthus within a 5-km radius of the Kikuchigawa River basin located in southern Japan. Seven spontaneous triploids, including five representative strains in the Kikuchigawa River basin, had the chromosome number and nuclear DNA content comparable with those of triploid M. × giganteus, and showed the amplification of species-specific DNA fragments from both parent species in DNA marker analysis. These demonstrated that these spontaneous strains were natural triploid hybrids. A 2-year-long field experiment in a warm climate revealed that these triploid hybrids showed phenotypic variation in agronomic and morphological traits. In addition, phylogenetic analysis of chloroplast DNA sequences revealed that these triploid hybrids had a polyphyletic origin but that all seven hybrids contained cytoplasm from M. sacchariflorus. The present study suggests that naturally occurring triploid hybrids could be more widely distributed in southern Japan than previously reported and be important breeding resources to develop Miscanthus cultivars with novel characteristic traits.