Author:
Dvořák Jan,Lassner M. W.,Kota R. S.,Chen K. C.
Abstract
Triticum speltoides (Tausch) Gren. ex Richter and Elytrigia elongata (Host) Nevski have two pairs of chromosomes with nucleolus organizing regions (NORs) which are the sites of the 18S and 26S ribosomal RNA (rRNA) genes. The relationships of the T. speltoides NORs to those of T. aestivum L. were determined by hybridizing an rRNA gene probe in situ in meiotic chromosomes of hybrids T. aestivum double ditelosomics × T. speltoides. The T. speltoides NORs were shown to be, as in the B genome of wheat, in the p arms of chromosomes 1 and 6. The chromosomal distribution of the E. elongata rRNA genes was determined from restriction fragment length polymorphism of the nontranseribed spacer using restriction endonuclease digested genomic DNAs from a T. aestivum × E. elongata amphiploid, disomic substitutions, and ditelosomic additions of E. elongata chromosomes in T. aestivum. Three approximately equally abundant spacer variants, 2.4, 2.0, and 1.0 kilobases (kb) long were observed in the E. elongata genotype present in the amphiploid. The copies of the 2.4 kb variant were in the short arm of chromosome 5E. whereas the copies of the 2.0- and 1.0-kb variants were in the p arm of chromosome 6E. This homogeneity within a chromosome and contrasting heterogeneity between nonhomologous chromosomes indicates that nucleotide sequence homogenization which governs the concerted evolution of the rRNA genes in E. elongata is more efficient within a chromosome than between chromosomes.Key words: rRNA genes, spacer, in situ hybridization, concerted evolution. Triticum, Elytrigia.
Publisher
Canadian Science Publishing
Subject
Cell Biology,Plant Science,Genetics
Cited by
21 articles.
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