Genetic studies of .ALPHA.-amylase isozymes in wheat VII. Variation in diploid ancestral species and phylogeny of tetraploid wheat

Distribution of highly repeated DNA sequences in species of the genus Secale

The presence and distribution of the most important highly repetitive DNA sequences of rye in cultivated and wild species of the genus Secale were investigated using fluorescence in situ hybridization. Accurate identification of individual chromosomes in the most commonly recognized species or subspecies of the genus Secale (S. cereale, S. ancestrale, S. segetale, S. afghanicum, S. dighoricum, S. montanum, S. montanum ssp. kuprijanovii, S. africanum, S. anatolicum, S. vavilovii, and S. silvestre) was achieved using three highly repetitive rye DNA sequences (probes pSc119.2, pSc74, and pSc34) and the 5S ribosomal DNA sequence pTa794. It is difficult to superimpose trends in the complexity of repetitive DNA during the evolution of the genus on conclusions from other cytogenetic and morphological assays. However, there are two clear groups. The first comprises the self-pollinated annuals S. silvestre and S. vavilovii that have few repeated nucleotide sequences of the main families of 120 and 480 bp. The second group presents amplification and interstitialization of the repeated nucleotide sequences and includes the perennials S. montanum, S. anatolicum, S. africanum, and S. kuprijanovii, as well as the annual and open-pollinated species S. cereale and its related weedy forms. The appearance of a new locus for 5S rRNA in S. cereale and S. ancestrale suggests that cultivated ryes evolved from this wild weedy species.

Comparison of the primary structure of waxy proteins (granule-bound starch synthase) between polyploid wheats and related diploid species

The waxy proteins encoded by the genomes A, B, and D in polyploid wheats and related diploid species were isolated by SDS-PAGE. The N-terminal amino acid sequences of mature proteins and V8 protease-induced fragments were determined. A total of five amino acid substitutions was detected in these sequences, which represent about 10% of the whole sequences of the waxy proteins. A comparison of these sequences in polyploid wheats with those in related diploid species revealed the following: (i) waxy proteins encoded by the A genome of polyploid wheats were identical to that of Triticum monococcum, (ii) the waxy protein encoded by the B genome of T. turgidum was identical to that of T. searsii, but differed from those of T. speltoides and T. longissimum by one amino acid substitution, (iii) the waxy protein encoded by the B genome of T. aestivum differed from that encoded by the B genome of T. turgidum by one amino acid substitution, and (iv) the waxy protein encoded by the D genome of T. aestivum was identical to that of T. tauschii.