2009 Volume 59 Issue 5 Pages 611-616
A hexaploid form of Hordeum brachyantherum ssp. brachyantherum was discovered in California in 1980, and its origin has since been studied over the past three decades. We applied EF-G, a nuclear DNA sequence, to infer the parents of the hexaploid form. In polyploid taxa, amplified DNAs were cloned into a vector, and EF-G copies were amplified from the colonies by PCR and digested with restriction enzymes to separate different types. Phylogenetic analysis was performed based on the DNA sequences. The result showed that H. brachyantherum ssp. brachyantherum 6x and 4x carried one identical DNA sequence of 910 bp, and had closely related DNA sequences of 931 bp. H. brachyantherum ssp. brachyantherum 6x and H. marinum ssp. gussoneanum 2x shared one identical DNA sequence of 915 bp. From these results we hypothesized that H. brachyantherum ssp. brachyantherum 6x has evolved by an outcrossing between H. marinum ssp. gussoneanum 2x and H. brachyantherum ssp. brachyantherum 4x, followed by a chromosome doubling. Our results also indicate that H. marinum was involved in the polyploidization of H. secalinum, H. capense, and H. marinum. The origins of H. jubatum and H. depressum are discussed.
