Genetic Diversity in Miscanthus ×giganteus

Miscanthus ×giganteus (Mxg) is a high-biomass producing perennial grass that is a hybrid between M. sinensis (Msi) and M. sacchariflorus (Msa). Numerous clones of sterile triploid Mxg have been named in Europe and North America, but it is unclear how much genetic diversity is present among them. Mxg was introduced to Denmark from Japan in 1935 and we hypothesize that nearly all of the differently named clones in Europe and North America were derived from this introduction. We quantified genetic variation using 38 SSR markers previously mapped onto Msi chromosomes (2/chromosome). Plant material studied included 33 triploid Mxg accessions of unknown provenance, 8 colchicine-induced hexaploids of Mxg ‘Illinois’, 7 diploid Msi, 12 diploid Msa, 1 colchicine-induced tetraploid Msa, 18 natural “Ogi type” tetraploid Msa from Japan, and 8 new triploid hybrids between diploid Msi and tetraploid Msa. For 87 accessions, 161 different alleles were scored. Out of 33 differently-named triploid Mxg, 30 showed 100% identity to the taxonomic type specimen, including ‘Illinois’, ‘Freedom’, and ‘EMI01’. Differences were found in 3 accessions for one of 38 SSR tested (97% identity). In contrast, genetic similarity to the type specimen for four full-sib triploid Mxg progeny from a cross recently produced at the Univ. of Illinois, three natural hybrids found in Southern Japan, and ‘Nagara’ was only 38-56%, 41-50%, and 38%, respectively. Thus, genetic diversity within the group of differently named Mxg accessions from America and Europe is nearly non-existent. New crosses will provide much-needed genetic variation for this emerging biomass crop.