Abstract
We focus on the identification of complete and recombined ribosomal DNA-bearing chromosomes, and the dynamics of chromosomal number and position of ribosomal DNA (rDNA) loci in the F2-F4 generations derived from the F1 hybrid of Festuca pratensis Huds. (2n = 4x = 28) × Lolium perenne L. (2n = 4x = 28). Lolium genomic DNA and rRNA genes were mapped by means of genomic and fluorescence in situ hybridization (GISH and FISH). The results revealed that plants of the three generations share various rDNA loci profiles with chromosome structural changes, possibly as a result of chromosomal inter- and intra-rearrangements. We observed an asymmetrical variation in the number of recombinant arms with and without rDNA loci between parental genomes. The Lolium genome was more affected by rearrangements in arms with rDNA loci, while Festuca was more affected in arms without them. Statistically significant differences between L. perenne and F. pratensis genomes concerned the number of recombined chromosomes without rDNA, and the number of recombined rDNA-bearing chromosomal arms of marked chromosomes, showing a tendency of F. pratensis genome-like chromosomes to be less stable, compared with L. perenne. We postulate a novel genome-dependent range and type of chromosome variation in plants of the F2-F4 generations derived from F. pratensis × L. perenne hybrid.Electronic supplementary materialThe online version of this article (doi:10.1007/s00709-014-0734-9) contains supplementary material, which is available to authorized users.
Highlights
We focus on the identification of complete and recombined ribosomal DNA-bearing chromosomes, and the dynamics of chromosomal number and position of ribosomal
In one F2 plant, the additional small 5S ribosomal DNA (rDNA) locus was distally located in the recombinant undifferentiated L. perenne (Lp) chromosome, but the recombinant Lp chromosome was apparently lost in later generations
They show the independent character of rDNA loci patterns within L. perenne and F. pratensis genomes
Summary
We focus on the identification of complete and recombined ribosomal DNA-bearing chromosomes, and the dynamics of chromosomal number and position of ribosomal. In the study of different plant genomes, including cultivars and inter-generic hybrids of the Festuca-Lolium complex, the possibility to identify mitotic and meiotic chromosomes is of major importance Modern cytogenetic analyses, such as fluorescence and genomic in situ hybridization (FISH and GISH) techniques, have been widely used to resolve many processes of chromosome evolution, including structural rearrangements (Levin 2004), as well as extensive studies on phylogenetic and genomic relationships (Robledo et al 2009), and to enhance our knowledge of plant genome structure and differentiation (D’Hont 2005; Maluszynska and Hasterok 2005; Cai et al 2006; Zwierzykowski et al 2008; Wolny et al 2011; Wan et al 2012; Chacón et al 2012). Studies of genome instability in the Festuca-Lolium complex has differentiated genetically close genomes such as Lolium multiflorum and
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