Apparent sources of the A genomes of wheats inferred from polymorphism in abundance and restriction fragment length of repeated nucleotide sequences

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Abstract
Four hundred random DNA fragment clones of wild diploid wheat Triticum monococcum ssp. aegilopoides (syn. T. baeoticum) were screened for clones of repeated nucleotide sequences. Seven DNA fragments were isolated that were more abundant by one order of magnitude or more in the genome of diploid T. monococcum ssp. aegilopoides (genome A) than in the genome of diploid Triticum speltoides (genome BS). These clones were then used to determine which of the two wild diploid wheats, T. m. ssp. aegilopoides or T. urartu, was the ancestor of domesticated diploid wheat T. m. ssp. monococcum, wild tetraploid wheats T. turgidum ssp. dicoccoides and T. timopheevii ssp. araraticum, domesticated tetraploid wheat T. turgidum, and hexaploid bread wheat T. aestivum. Three of the seven cloned repeated nucleotide sequences differentiated the genome of T. m. ssp. aegilopoides from that of T. urartu in repeated sequence abundance, restriction fragment length polymorphism, or both. The same distinctions were observed between the A genome of T. m. ssp. aegilopoides and the A genomes of polyploid wheats. From this it was concluded that the species from which T. m. ssp. monococcum was domesticated was T. m. ssp. aegilopoides but that the A genomes of the polyploid wheats are equivalent to that of T. urartu. The results presented here demonstrate the utility of polymorphism in repeated nucleotide sequences in the investigation of the origin of genomes in polyploid plants.Key words: RFLP, Triticum, wheat phylogeny.