Population Structure of Miscanthus sacchariflorus and Patterns of Hybridization with M. sinensis

Miscanthus, a C₄ perennial grass native to East Asia, is a promising crop for biomass and bioenergy. Here we report the findings of the largest population genetic study to date of M. sacchariflorus, including 764 individuals collected from 28.6 to 49.3° N and 104.5 to 145.2° E. Samples were genotyped with 34,605 RAD-seq SNPs and ten plastid microsatellites, and were subjected to ploidy analysis by flow cytometry. Six major genetic groups were identified using SNP data: three diploid groups including Yangtze (ssp. lutarioriparius), N China, and NE China/Korea/Russia; and three tetraploid groups including N China/Korea, S Japan, and N Japan. SNP and plastid data suggest that the land mass that now includes the Yellow Sea was a center of diversity for M. sacchariflorus during the last glacial maximum. M. sacchariflorus ssp. lutarioriparius was derived from the N China group with a substantial bottleneck. Similarities among groups using both SNP and plastid data suggest that Japanese and mainland tetraploids originated from independent polyploidization events. Moreover, tetraploid M. sacchariflorus in S Japan and Korea exhibit substantial hybridization with and introgression from diploid M. sinensis, which contribute to their high genetic diversity. We also found hybrids between diploid M. sacchariflorus and M. sinensis in Korea, but without introgression into either parent species. Although genetic diversity is virtually non-existent in ornamental M. sacchariflorus, wild M. sacchariflorus has greater genetic diversity than M. sinensis, suggesting that breeding and selection of M. sacchariflorus will be important for the development of improved M. ×giganteus.