Abstract
The genus Rosa Linnaeus, 1753 has important economic value in ornamental sector and many breeding activities are going on supported by molecular studies. However, the cytogenetic studies of rose species are scarce and mainly focused on chromosome counting and chromosome morphology-based karyotyping. Due to the small size of the chromosomes and a high frequency of polyploidy in the genus, karyotyping is very challenging for rose species and requires FISH-based cytogenetic markers to be applied. Therefore, in this work the aim is to establish a FISH-based karyotype for Rosa wichurana (Crépin, 1888), a rose species with several benefits for advanced molecular cytogenetic studies of genus Rosa (Kirov et al. 2015a). It is shown that FISH signals from 5S, 45S and an Arabidopsis-type telomeric repeat are distributed on five (1, 2, 4, 5 and 7) of seven chromosome pairs. In addition, it is demonstrated that the interstitial telomeric repeat sequences (ITR) are located in the centromeric regions of four chromosome pairs. Using low hybridization stringency for ITR visualization, we showed that the number of ITR signals increases four times (1–4 signals). This study is the first to propose a FISH-based Rosa wichurana karyotype for the reliable identification of chromosomes. The possible origin of Rosa wichurana ITR loci is discussed.
Highlights
Rosa Linnaeus, 1753 is an economically important ornamental genus belonging to the Rosaceae
This study aims to explore the opportunities of interstitial telomeric repeat sequences (ITR), 5S and 45S rDNA as cytogenetic markers allowing to distinguish individual chromosomes of Rosa
FISH using the common hybridisation temperature of 37°C with 45S rDNA revealed a signal on chromosome 7, while the Arabidopsis type telomere-based probe hybridized on chromosome 5 (Fig. 1A)
Summary
Rosa Linnaeus, 1753 is an economically important ornamental genus belonging to the Rosaceae. Rosa wichurana (Crépin, 1888) is a valuable model species for molecular cytogenetic studies in Rosa genus (Kirov et al 2015b). It is a diploid species (2n = 2x = 14) with suitable apical and root meristems that can be used for chromosome preparations. To increase the efficiency of FISH experiments, we recently developed the “SteamDrop” protocol for the preparation of high quality chromosome slides (Kirov et al 2014b) Using this “SteamDrop” protocol and Tyramide-FISH it was possible to physically map several single-copy genes on the mitotic and meiotic chromosomes of R. wichurana (Kirov et al 2014a, Kirov et al 2015a) and to anchor three linkage groups of the genetic map (Moghaddam et al 2012) to three R. wichurana chromosomes
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