CO/Hd1 Homologs in Miscanthus sacchariflorus from the East Asia Mainland, Eastern Russia and Japanese Archipelago

Miscanthus spp. are the most candidate bioenergy crop in cool temperate regions. Flowering time is a key target trait for extending the vegetative phase to improve biomass potential. CONSTANS (CO) and Heading Date 1 (Hd1) are central regulators for flowering pathway. CO/Hd1 homologs from Miscanthus sacchariflorus (MsaHd1) were compared among M. sacchariflorus accessions including four diploid, seven tetraploid and two triploid strains as well as one M. lutarioriparius, which were collected from China, Korea, Russia and Japan. Four to eight MsaHd1 alleles in each accession were identified, and based on the open reading frame in MsaHd1, each allele was classified as putative functional alleles or non-functional alleles. The neighbor-joining tree formed two major clades; MsaHd1a multi-locus families with functional alleles and MsaHd1b with non-functional alleles being similar with M. sinensis; MsiHd1a and MsiHd1b. For MsaHd1b, newly generated stop codon (TAG) by insertion of 3bp (GTA) in exon 1 was a major mutation. Diploid M. sacchariflorus "robustus" lost STOP codon by point mutation, and it recovered the open reading frame. Parents of triploid hybrids were derived from both M. sinensis and M. sacchariflorus distributed in Japan. Our previous analysis revealed that many M. sinensis populations in Japan have MsiHd1a with loss-of-function type alleles. The triploid hybrids inherited the allele of M. sacchariflorus MsaHd1a with function preferentially. This suggests the possibility that segregation distortion has occurred in the vicinity regions containing CO/Hd1 loci. We will discuss the differentiation of populations of M. sacchariflorus in term of allelic distribution of CO/Hd1.