Molecular Karyotyping on Populus simonii × P. nigra and the Derived Doubled Haploid.

Bo Liu,Xiaoyan Tao,Caixia Liu,Quanwen Dou,Sui Wang,Guanzheng Qu

doi:10.3390/ijms222111424

Abstract

The molecular karyotype could represent the basic genetic make-up in a cell nucleus of an organism or species. A doubled haploid (DH) is a genotype formed from the chromosome doubling of haploid cells. In the present study, molecular karyotype analysis of the poplar hybrid Populus simonii × P. nigra (P. xiaohei) and the derived doubled haploids was carried out with labeled telomeres, rDNA, and two newly repetitive sequences as probes by fluorescence in situ hybridization (FISH). The tandem repeats, pPC349_XHY and pPD284_XHY, with high-sequence homology were used, and the results showed that they presented the colocalized distribution signal in chromosomes. For P. xiaohei, pPD284_XHY produced hybridizations in chromosomes 1, 5, 8, and 9 in the hybrid. The combination of pPD284_XHY, 45S rDNA, and 5S rDNA distinctly distinguished six pairs of chromosomes, and the three pairs of chromosomes showed a significant difference in the hybridization between homologous chromosomes. The repeat probes used produced similar FISH hybridizations in the DH; nevertheless, pPD284_XHY generated an additional hybridization site in the telomere region of chromosome 14. Moreover, two pairs of chromosomes showed differential hybridization distributions between homologous chromosomes. Comparisons of the distinguished chromosomes between hybrid and DH poplar showed that three pairs of chromosomes in the DH presented hybridization patterns that varied from those of the hybrid. The No. 8 chromosome in DH and one of the homologous chromosomes in P. xiaohei shared highly similar FISH patterns, which suggested the possibility of intact or mostly partial transfer of the chromosome between the hybrid and DH. Our study will contribute to understanding the genetic mechanism of chromosomal variation in P. xiaohei and derived DH plants.

Highlights

Poplar (Populus spp.), a genus in the family Salicaceae, is widely distributed in most of the Northern Hemisphere due to its rapid growth, stress resistance, and economic importance [1]
Populus simonii × P. nigra is an artificial hybrid crossed with P. simonii Carr (Tacamahaca) as the maternal plant and P. nigra L. (Aigeiros) as the paternal plant [4]
We obtained approximately 57.2 and 54.3 Gb raw reads for the heterozygous parent and the doubled haploid (DH) plants of Populus, respectively

Summary

Introduction

Poplar (Populus spp.), a genus in the family Salicaceae, is widely distributed in most of the Northern Hemisphere due to its rapid growth, stress resistance, and economic importance [1]. This genus has traditionally been divided into six sections based on leaf, flower, and other characteristics, but five major subclades have been recovered based on recent genetic studies [2,3]. Haploid and doubled haploid (DH) plants play an important role in breeding, genetics, molecular biology, and genomics These plants are adapted for mutagenesis and genetic transformation experiments, presenting the advantage of the immediate production of homozygous lines. DH plants were successfully developed from the anther of P. xiaohei in our lab and are regarded as important germplasms for basic research and breeding

Methods

Results

Discussion

Conclusion