Phenotypic, cytogenetic, and molecular marker analysis of Brassica napus introgressants derived from an intergeneric hybridization with Orychophragmus.

Chuanyuan Xu,Qian Huang,Xianhong Ge,Zaiyun Li,Yong Pyo Lim

doi:10.1371/journal.pone.0210518

Chuanyuan Xu, Qian Huang + Show 3 more

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https://doi.org/10.1371/journal.pone.0210518

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Journal: PloS one	Publication Date: Jan 10, 2019
Citations: 8	License type: CC BY 4.0

Affiliation: Huazhong Agricultural University

Abstract

Aneuploids of a single species that have lost or gained different chromosomes are useful for genomic analysis. The polyploid nature of many crops including oilseed rape (Brassica napus) allows these plants to tolerate the loss of individual chromosomes from homologous pairs, thus facilitating the development of aneuploid lines. Here, we selected 39 lines from advanced generations of an intergeneric hybridization between Brassica rapa and Orychophragmus violaceus with accidental pollination by B. napus. The lines showed a wide spectrum of phenotypic variations, with some traits specific to O. violaceus. Most lines had the same chromosome number (2n = 38) as B. napus. However, we also identified B. napus nulli-tetrasomics with 22 A-genome and 16 C-genome chromosomes and lines with the typical B. napus complement of 20 A-genome and 18 C-genome chromosomes, as revealed by FISH analysis using a C-genome specific probe. Other lines had 2n = 37 or 39 chromosomes, with variable numbers of A- or C-genome chromosomes. The formation of quadrivalents by four A-genome chromosomes with similar shapes suggests that they were derived from the same chromosome. The frequent homoeologous pairing between chromosomes of the A and C genomes points to their non-diploidized meiotic behavior. Sequence-related amplified polymorphism (SRAP) analysis revealed substantial genomic changes of the lines compared to B. rapa associated with O. violaceus specific DNA bands, but only a few genes were identified in these bands by DNA sequencing. These novel B. napus aneuploids and introgressants represent unique tools for studies of Brassica genetics and for Brassica breeding projects.

Highlights

Maintaining a balanced euploid genome is a key feature of all multicellular organisms
The spectrum of phenotypes ranged from B. rapa-type to O. violaceus-type, with most being intermediate
Most lines flowered at similar times to B. rapa ‘Aijiaohuang’ but earlier than winter type B. napus, which requires approximately 150 days for flowering

Summary

Introduction

Maintaining a balanced euploid genome is a key feature of all multicellular organisms. The most common viable form of aneuploidy in humans is Down syndrome, which results from the presence of a third copy of chromosome 21 in a diploid background. This syndrome is typically associated with a delay in cognitive ability and physical growth, as well as a particular set of facial characteristics [6]. Various types of dosage compensation can affect plant autosomes, allowing them to better tolerate gene copy imbalances [7]. These aneuploids exhibit few or subtle phenotypic abnormalities and can often compete with their euploid progenitors [8]. Plants provide an excellent opportunity for genome-wide investigations of aneuploid syndromes [9,10,11,12]

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