Distinct subgenome stabilities in synthesized Brassica allohexaploids

Zhou, Jiannan; Tan, Chen; Cui, Cheng; Ge, Xianhong; Li, Zaiyun

doi:10.1007/s00122-016-2701-7

Cited by 52 publications

(48 citation statements)

References 41 publications

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“…A . C) were also observed in the synthesized Brassica allohexaploids (2n = 54, AABBCC), after being pollinated by O. violaceus (Ge et al 2009) or after self-pollinations of successive generations (Zhou et al 2016). The distinct behaviors of these genomes were possibly attributable to their differences in size, inherent cytology, and homeology (Zhou et al 2016).…”

Section: Discussionmentioning

confidence: 86%

Extraction of the Constituent Subgenomes of the Natural Allopolyploid Rapeseed (Brassica napus L.)

Zhu

Zeng

et al. 2016

Genetics

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As the dynamic nature of progenitor genomes accompanies the speciation by interspecific hybridization, the extraction of the constituent subgenome(s) from a natural allopolyploid species of long history and then restitution of the progenitor(s) provides the unique opportunity to study the genome evolution and interplay. Herein, the A subgenome from the allotetraploid oilseed rape (Brassica napus L., AACC) was extracted through inducing the preferential elimination of C-subgenome chromosomes in intertribal crosses and the progenitor B. rapa was restituted (RBR). Then by crossing and backcrossing RBR with B. napus donor, the C subgenome was in situ dissected by adding each of its nine chromosomes to the extracted A subgenome and establishing the whole set of monosonic alien addition lines (MAALs). RBR from spring-type B. napus genotype "Oro" expressed a phenotype resembling some type of B. rapa never observed before, but showed a winter-type flowering habit. This RBR had weaker growth vigor and suffered more seriously from biotic and abiotic stresses compared with Oro. The phenotypes specific for these MAALs showed the location of the related genes on the particular C-subgenome chromosomes. These MAALs exhibited obviously different frequencies in homeologous pairing and transmission of additional C-subgenome chromosomes, which were associated with the distinct degrees of their relatedness, and even with the possible genetic regulation for meiotic pairing evolved in B. napus. Finally, large scaffolds undetermined for sequence assembly of B. napus were anchored to specific C-subgenome chromosomes using MAALs.KEYWORDS allopolyploid; Brassica napus; B. rapa; alien additional lines; aneuploid M ANY angiosperms including important crops (bread wheat, cotton, oilseed rape, tobacco, etc.) are allopolyploid species that originated from interspecific hybridizations between two or more diploid ancestors followed by chromosome doubling (Ramsey and Schemske 1998;Levin 2003;Otto 2007;Doyle et al. 2008;Soltis and Soltis 2012). These allopolyploid crops outcompete their progenitors by their adaptability to a wide range of climatic conditions and higher yield and better quality of targeted products, under human domestication and improvement. To unravel the origin and structure of the component genomes in these crops has been the goal of the extensive genetic research over a long period. The hybridization events leading to the evolutionary origin of these allopolyploids were traditionally elucidated by the artificial synthesis of their counterparts from the crosses between the extant relatives of the presumed progenitors available or by observing the meiotic chromosome pairing in the hybrids between the natural allopolyploid and the possible progenitors (Kihara 1924;Nagaharu 1935). Alternatively, the genome of one progenitor (AA) was readily dissected by separating and adding its own chromosome to the genome of another progenitor (BB) (namely the alien addition lines), from successively backcrossing the natural or synthesi...

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Section: Discussionmentioning

confidence: 86%

Extraction of the Constituent Subgenomes of the Natural Allopolyploid Rapeseed (Brassica napus L.)

Zhu

Zeng

et al. 2016

Genetics

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“…The 36 chromosomes were expected to consist of the total 2 A and 2 B genomes, without any of the C genome chromosome. When the genome of A, B and C was integrated in hexaploids, the C genome was more easily lost because the genome stability was B>A>C (Zhou et al, 2016). The pedigrees of the introgressed lines were established according to the original interspecific crosses for the pentaploids.…”

Section: Resultsmentioning

confidence: 99%

Introgressing Subgenome Components from Brassica rapa and B. carinata to B. juncea for Broadening Its Genetic Base and Exploring Intersubgenomic Heterosis

Wei¹,

Wang²,

Chang³

et al. 2016

Front. Plant Sci.

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Brassica juncea (AjAjBjBj), is an allotetraploid that arose from two diploid species, B. rapa (ArAr) and B. nigra (BnBn). It is an old oilseed crop with unique favorable traits, but the genetic improvement on this species is limited. We developed an approach to broaden its genetic base within several generations by intensive selection. The Ar subgenome from the Asian oil crop B. rapa (ArAr) and the Bc subgenome from the African oil crop B. carinata (BcBcCcCc) were combined in a synthesized allohexaploid (ArArBcBcCcCc), which was crossed with traditional B. juncea to generate pentaploid F1 hybrids (ArAjBcBjCc), with subsequent self-pollination to obtain newly synthesized B. juncea (Ar/jAr/jBc/jBc/j). After intensive cytological screening and phenotypic selection of fertility and agronomic traits, a population of new-type B. juncea was obtained and was found to be genetically stable at the F6 generation. The new-type B. juncea possesses good fertility and rich genetic diversity and is distinctly divergent but not isolated from traditional B. juncea, as revealed by population genetic analysis with molecular markers. More than half of its genome was modified, showing exotic introgression and novel variation. In addition to the improvement in some traits of the new-type B. juncea lines, a considerable potential for heterosis was observed in inter-subgenomic hybrids between new-type B. juncea lines and traditional B. juncea accessions. The new-type B. juncea exhibited a stable chromosome number and a novel genome composition through multiple generations, providing insight into how to significantly broaden the genetic base of crops with subgenome introgression from their related species and the potential of exploring inter-subgenomic heterosis for hybrid breeding.

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“…In Mason et al (2014), near-allohexaploid Brassica hybrid populations with variable fertility and chromosome inheritance were produced from the species combination (B. Zhou et al (2016) synthesised Brassica allohexaploids that were created using three different crossing strategies, and investigation was carried out over several generations. In this study euploid and aneuploid progenies were produced and were used to investigate genomic stability, which was found to follow the B > A > C pattern.…”

Section: Allohexaploid Brassicamentioning

confidence: 99%

“…Recent studies with Brassica allohexaploids from different genotype combinations, including the B. rapa and B. carinata crosses, suggest increased fertility and stability may arise in subsequent generations (Tian et al 2010;Zhou et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Creating a new allohexaploid Brassica crop:determination of fertility and stability in novel Brassica hybrids

Mwathi¹

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The Brassica genus is an economically important group of diploid (single genome) and allotetraploid (two-genome) species used as oilseeds, vegetables and condiments. Although no allohexaploid (three-genome) Brassica species exists in nature, the production of an allohexaploid Brassica crop could be beneficial for agriculture. However, production of a stable and fertile Brassica allohexaploid is currently hindered by challenges of infertility and unstable meiosis. To date, incremental progress has been made in creating an allohexaploid species using several different species combinations. Despite this, a gap in knowledge currently exists for genomic stability among Brassica allohexaploids, critical in the establishment of a successful species. Firstly, I investigated fertility and meiotic stability in 100 plants from the cross B. carinata × B. rapa (A2 allohexaploid population) and 69 plants from the cross (B. napus × B. carinata) × B. juncea (H2 allohexaploid population). Estimated pollen viability, self-pollinated seed set, number of seeds on the main shoot, number of pods on the main shoot, seeds per 10 pods and plant height were measured for both the A2 and H2 populations and a set of reference control cultivars. The H2 population had high segregation for pollen viability and meiotic stability, while the A2 population was characterised by low pollen fertility and a high level of chromosome loss. Both populations were taller, but had lower average fertility trait values, than the control cultivar samples. Additionally, I established that the genotypes of the parents and H1 hybrids are affecting chromosome pairing and fertility phenotypes in the H2 population. Next, I investigated fertility, meiosis and genetic variability in sets of self-pollinated progenies (the MDL2 population) resulting from first generation microspore-derived plants (the MDL1 population). These populations were derived from microspores of a near-allohexaploid interspecific hybrid plant from the cross (Brassica napus × B. carinata) × B. juncea. Fertility decreased from MDL1 to MDL2 population, with several fixed chromosome duplications and deletions present as well as novel genomic events seen to have occurred from the MDL1 to MDL2. Genetic non-identity between lines within various progeny sets in MDL2 was also observed, uncharacteristic of what would be expected of a microspore-derived (normally doubled haploid; DH) population. iii Finally, I made novel interspecific hybrids between wild C genome species, B. oleracea and B. juncea to utilise this germplasm for the creation of a diverse allohexaploid species. Hand pollinations between two genotypes of B. juncea (Xingyou 4 and B578) and B. oleracea (TO1000) and wild C genome species B. incana, B. montana and B. cretica were performed (747 total bud pollinations, average 62.25 per cross combination) in both cross directions. The combination with B. oleracea produced six triploid hybrids (2n = ABC) from 85 flower pollinations. Pollen fertility in triploid hybrids was low; between 2 -10% (averag...

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Distinct subgenome stabilities in synthesized Brassica allohexaploids

Cited by 52 publications

References 41 publications

Extraction of the Constituent Subgenomes of the Natural Allopolyploid Rapeseed (Brassica napus L.)

Extraction of the Constituent Subgenomes of the Natural Allopolyploid Rapeseed (Brassica napus L.)

Introgressing Subgenome Components from Brassica rapa and B. carinata to B. juncea for Broadening Its Genetic Base and Exploring Intersubgenomic Heterosis

Creating a new allohexaploid Brassica crop:determination of fertility and stability in novel Brassica hybrids

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