title: Cytogenetic Diversity of Simple Sequences Repeats in Morphotypes of Brassica rapa ssp. chinensis.
abstract: A significant fraction of the nuclear DNA of all eukaryotes is comprised of simple sequence repeats (SSRs). Although these sequences are widely used for studying genetic variation, linkage mapping and evolution, little attention had been paid to the chromosomal distribution and cytogenetic diversity of these sequences. In this paper, we report the distribution characterization of mono-, di-, and tri-nucleotide SSRs in Brassica rapa ssp. chinensis. Fluorescence in situ hybridization was used to characterize the cytogenetic diversity of SSRs among morphotypes of B. rapa ssp. chinensis. The proportion of different SSR motifs varied among morphotypes of B. rapa ssp. chinensis, with tri-nucleotide SSRs being more prevalent in the genome of B. rapa ssp. chinensis. We determined the chromosomal locations of mono-, di-, and tri-nucleotide repeat loci. The results showed that the chromosomal distribution of SSRs in the different morphotypes is non-random and motif-dependent, and allowed us to characterize the relative variability in terms of SSR numbers and similar chromosomal distributions in centromeric/peri-centromeric heterochromatin. The differences between SSR repeats with respect to abundance and distribution indicate that SSRs are a driving force in the genomic evolution of B. rapa species. Our results provide a comprehensive view of the SSR sequence distribution and evolution for comparison among morphotypes B. rapa ssp. chinensis.
authors: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, Ministry of Horticulture, Nanjing Agricultural University, NanjingChina; Hebei Normal University of Science and Technology, QinhuangdaoChina.
authors: Jin-Shuang
authors: JS
authors: Zheng
authors: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, Ministry of Horticulture, Nanjing Agricultural University, NanjingChina; Hebei Normal University of Science and Technology, QinhuangdaoChina.
authors: Cheng-Zhen
authors: CZ
authors: Sun
authors: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, Ministry of Horticulture, Nanjing Agricultural University, Nanjing China.
authors: Shu-Ning
authors: SN
authors: Zhang
authors: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, Ministry of Horticulture, Nanjing Agricultural University, Nanjing China.
authors: Xi-Lin
authors: XL
authors: Hou
authors: Wageningen UR Plant Breeding, Wageningen University and Research Centre, Wageningen Netherlands.
authors: Guusje
authors: G
authors: Bonnema
keywords: Brassica rapa; cytogenetic diversity; fluorescence in situ hybridization; heterochromatin; simple sequence repeats