Elucidation of the B-genome donor to Triticum turgidum by unique- and repeated-sequence DNA hybridizations.

In vitro DNA:DNA hybridizations and hydroxyapatite thermal-elution chromatography were employed to identify the diploid Triticum species ancestral to the B genome of T. turgidum. Unique and repeated sequences from the various Triticum species were separated by hybridization and thermal elution on hydroxyapatite. Unique- and repeated-sequence fractions of labeled T. turgidum var. durum DNA were hybridized to the corresponding fractions of unlabeled DNAs of T. searsii, T. speltoides, T. longissimum, T. sharonensis, and T. bicorne. Thermal stability profiles were constructed to evaluate base-sequence complementarity between T. turgidum var. durum and the diploid Triticum species. The heteroduplex thermal stabilities indicated that, of the five species examined, T. searsii was the most closely related to the B genome of T. turgidum var. durum. The thermal stability profiles further indicated that the repeated DNA fractions from the Triticum species are more similar than the unique-sequence fractions. This indicates that all of the Triticum species are very closely related and, in all probability, have diverged from a single progenitor species.