title: The fate of chromosomes and alleles in an allohexaploid Brassica population.
abstract: Production of allohexaploid Brassica (2n = AABBCC) is a promising goal for plant breeders due to the potential for hybrid heterosis and useful allelic contributions from all three of the Brassica genomes present in the cultivated diploid (2n = AA, 2n = BB, 2n = CC) and allotetraploid (2n = AABB, 2n = AACC, and 2n = BBCC) crop species (canola, cabbages, mustards). We used high-throughput SNP molecular marker assays, flow cytometry, and fluorescent in situ hybridization (FISH) to characterize a population of putative allohexaploids derived from self-pollination of a hybrid from the novel cross (B. napus × B. carinata) × B. juncea to investigate whether fertile, stable allohexaploid Brassica can be produced. Allelic segregation in the A and C genomes generally followed Mendelian expectations for an F2 population, with minimal nonhomologous chromosome pairing. However, we detected no strong selection for complete 2n = AABBCC chromosome complements, with weak correlations between DNA content and fertility (r(2) = 0.11) and no correlation between missing chromosomes or chromosome segments and fertility. Investigation of next-generation progeny resulting from one highly fertile F2 plant using FISH revealed general maintenance of high chromosome numbers but severe distortions in karyotype, as evidenced by recombinant chromosomes and putative loss/duplication of A- and C-genome chromosome pairs. Our results show promise for the development of meiotically stable allohexaploid lines, but highlight the necessity of selection for 2n = AABBCC karyotypes.
authors.affiliation: School of Agriculture and Food Sciences and Centre for Integrative Legume Research, The University of Queensland, Brisbane Queensland 4072, Australia.
authors.forename: Annaliese S
authors.initials: AS
authors.lastname: Mason
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Nelson
authors.forename: Junko
authors.initials: J
authors.lastname: Takahira
authors.forename: Wallace A
authors.initials: WA
authors.lastname: Cowling
authors.forename: Gustavo Moreira
authors.initials: GM
authors.lastname: Alves
authors.forename: Arkaprava
authors.initials: A
authors.lastname: Chaudhuri
authors.forename: Ning
authors.initials: N
authors.lastname: Chen
authors.forename: Mohana E
authors.initials: ME
authors.lastname: Ragu
authors.forename: Jessica
authors.initials: J
authors.lastname: Dalton-Morgan
authors.forename: Olivier
authors.initials: O
authors.lastname: Coriton
authors.forename: Virginie
authors.initials: V
authors.lastname: Huteau
authors.forename: Frédérique
authors.initials: F
authors.lastname: Eber
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Chèvre
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Batley
mesh_terms: D000483:Alleles; D001937:Brassica / Q000166:cytology / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D032461:Chromosomes, Plant / Q000187:drug effects / Q000235:genetics*; D003078:Colchicine / Q000494:pharmacology; D018744:DNA, Plant / Q000235:genetics; D005298:Fertility / Q000187:drug effects / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics; D006824:Hybridization, Genetic; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008540:Meiosis / Q000187:drug effects / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D011123:Polyploidy
chemical_list: D018744:DNA, Plant; D003078:Colchicine
keywords: Brassica; Infinium 60K SNP chip; allohexaploid; chromosome behavior; molecular cytogenetics