A novel genome of C and the first autotetraploid species in the <Emphasis Type="Italic">Setaria</Emphasis> genus identified by genomic <Emphasis Type="Italic">in situ</Emphasis> hybridization

Genomic in situ hybridization (GISH) was used to investigate the genomic relationships among some newly collected species of genus Setaria. Previous work identified that S. viridis and S. adhaerens carry genomes A and B, respectively. GISH patterns obtained in this report clearly distinguished the genome of S. grisebachii from the known genomes A and B, and indicated its new genomic constitution which we suggest to name genome C of the Setaria genus. The two sets of chromosomes of tetraploid S. queenslandica hybridized well with the A genome of S. viridis indicating its autotetraploid nature. This is the first autotetraploid identified in the Setaria genus, which should be classified into the primary A genome gene pool rather than the tertiary gene pool as previously classified. GISH patterns did not distinguish the genome of S. leucopila from the A genome of S. viridis and S. italica, suggesting its close relation with foxtail millet. Strong hybridization signals were observed when S. adhaerens genomic DNA was used as probe to hybridize the chromosomes of diploid S. verticillata, inferring its B genome nature. Combined with morphological observation and previous work, we deduce that diploid S. verticillata and S. adhaerens are probably taxonomically the same species with different names. Y. Wang and H. Zhi contributed equally to this article.