Discovery of natural Miscanthus (Poaceae) triploid plants in sympatric populations of Miscanthus sacchariflorus and Miscanthus sinensis in southern Japan

Premise of the study: Looming petroleum shortages and projected negative impacts of human-induced climate change may be partly alleviated by the development and use of bioenergy feedstock crops. Miscanthus × giganteus, a highly productive sterile triploid hybrid grass that was discovered in Japan several decades ago, has considerable potential as an alternative source of energy. Given the risks, however, involved in the reliance upon production of one clone of this hybrid, which is a natural cross between Miscanthus sacchariflorus and Miscanthus sinensis, for lignocellulosic bioenergy production, natural occurrences of triploidy were investigated in sympatric populations of tetraploid M. sacchariflorus and diploid M. sinensis in Japan. Methods: Seeds were counted and DNA content was estimated by flow cytometry for plants of M. sacchariflorus and M. sinensis in several sympatric populations throughout Japan. Chromosomes were also counted for select plants. Key results: Based on seed-set data, M. sacchariflorus has significantly lower seed set than M. sinensis in Japan. Putative triploid seeds were found on M. sacchariflorus plants in southern Japan. Conclusions: This is the first report of the natural occurrence of Miscanthus triploid plants in several decades. If found to be sterile and similar in productivity to the commonly cultivated clone of M. × giganteus, these triploid plants might serve as additional sources of genetic variation for bioenergy production. Seed set data also indicates that other triploid plants might be found in more northern regions of Japan.