Twinned microspore-derived embryos of canola (Brassica napus L.) are genetically identical

Cousin, Anouska; Nelson, Matthew N.

doi:10.1007/s00299-009-0677-3

Cited by 17 publications

(8 citation statements)

References 13 publications

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“…Two pairs of twins were observed from marker results. These plants may have resulted from secondary embryogenesis generating identically twinned embryos during the tissue culture process (Raemakers et al 1995;Cousin and Nelson 2009); one of each pair was removed from the analysis. Of the remaining 84 individuals, 75 (89%) were heterozygous at 38-86% (average 68%) of loci in the A genome; heterozygosity was assessed as presence of both a B. juncea and a B. napus parental allele at a single A-genome locus (Figure 2A).…”

Section: Resultsmentioning

confidence: 99%

“…Of the 57 microspore-derived plants in 10 progeny sets with nonidentical haplotypes in Mason et al (2011a), an additional eight individuals were conservatively excluded for this study after SNP marker genotyping revealed that they may have been clones (.95% similar genetic identity) (Raemakers et al 1995;Cousin and Nelson 2009) (Table S1). An additional four clone pairs were also identified in the new microspore-derived progeny, and one of each pair was excluded from further analysis.…”

Section: Resultsmentioning

confidence: 99%

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Centromere Locations inBrassicaA and C Genomes Revealed Through Half-Tetrad Analysis

et al. 2015

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Locating centromeres on genome sequences can be challenging. The high density of repetitive elements in these regions makes sequence assembly problematic, especially when using short-read sequencing technologies. It can also be difficult to distinguish between active and recently extinct centromeres through sequence analysis. An effective solution is to identify genetically active centromeres (functional in meiosis) by half-tetrad analysis. This genetic approach involves detecting heterozygosity along chromosomes in segregating populations derived from gametes (half-tetrads). Unreduced gametes produced by first division restitution mechanisms comprise complete sets of nonsister chromatids. Along these chromatids, heterozygosity is maximal at the centromeres, and homologous recombination events result in homozygosity toward the telomeres. We genotyped populations of half-tetrad-derived individuals (from Brassica interspecific hybrids) using a high-density array of physically anchored SNP markers (Illumina Brassica 60K Infinium array). Mapping the distribution of heterozygosity in these half-tetrad individuals allowed the genetic mapping of all 19 centromeres of the Brassica A and C genomes to the reference Brassica napus genome. Gene and transposable element density across the B. napus genome were also assessed and corresponded well to previously reported genetic map positions. Known centromerespecific sequences were located in the reference genome, but mostly matched unanchored sequences, suggesting that the core centromeric regions may not yet be assembled into the pseudochromosomes of the reference genome. The increasing availability of genetic markers physically anchored to reference genomes greatly simplifies the genetic and physical mapping of centromeres using half-tetrad analysis. We discuss possible applications of this approach, including in species where half-tetrads are currently difficult to isolate.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Centromere Locations inBrassicaA and C Genomes Revealed Through Half-Tetrad Analysis

et al. 2015

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“…The mapping population (LMDH) used in this study was a doubled haploid (DH) B. napus population (n = 131) derived from reciprocal F1 hybrids created from two genetically-distinct parents (European summer annual-type ‘Lynx-037DH’ and an Australian summer annual-type ‘Monty-028DH’ [32], [33]) using the method described by Cousin and Nelson [34]. The parents were homozygous DH lines developed by microspore culture from the varieties ‘Lynx’ and ‘Monty’, respectively.…”

Section: Methodsmentioning

confidence: 99%

Quantitative Trait Loci for Thermal Time to Flowering and Photoperiod Responsiveness Discovered in Summer Annual-Type Brassica napus L

et al. 2014

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Time of flowering is a key adaptive trait in plants and is conditioned by the interaction of genes and environmental cues including length of photoperiod, ambient temperature and vernalisation. Here we investigated the photoperiod responsiveness of summer annual-types of Brassica napus (rapeseed, canola). A population of 131 doubled haploid lines derived from a cross between European and Australian parents was evaluated for days to flowering, thermal time to flowering (measured in degree-days) and the number of leaf nodes at flowering in a compact and efficient glasshouse-based experiment with replicated short and long day treatments. All three traits were under strong genetic control with heritability estimates ranging from 0.85–0.93. There was a very strong photoperiod effect with flowering in the population accelerated by 765 degree-days in the long day versus short day treatments. However, there was a strong genetic correlation of line effects (0.91) between the long and short day treatments and relatively low genotype x treatment interaction indicating that photoperiod had a similar effect across the population. Bivariate analysis of thermal time to flowering in short and long days revealed three main effect quantitative trait loci (QTLs) that accounted for 57.7% of the variation in the population and no significant interaction QTLs. These results provided insight into the contrasting adaptations of Australian and European varieties. Both parents responded to photoperiod and their alleles shifted the population to earlier flowering under long days. In addition, segregation of QTLs in the population caused wide transgressive segregation in thermal time to flowering. Potential candidate flowering time homologues located near QTLs were identified with the aid of the Brassica rapa reference genome sequence. We discuss how these results will help to guide the breeding of summer annual types of B. napus adapted to new and changing environments.

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“…In this study, parent genotypes were derived from a process of doubled-haploidy through microspore culture protocols described in Nelson et al (2009) [19] and Cousin and Nelson (2009) [39] and bulked by pure seed methods. The five B. napus genotypes were "Surpass400_024DH", "Trilogy", "Westar_010DH", "Monty_028DH" and "Boomer", and are hereafter referred to as N1, N2, N3, N4 and N5, respectively.…”

Section: Methodsmentioning

confidence: 99%

Production of viable male unreduced gametes in Brassica interspecific hybrids is genotype specific and stimulated by cold temperatures

et al. 2011

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BackgroundUnreduced gametes (gametes with the somatic chromosome number) may provide a pathway for evolutionary speciation via allopolyploid formation. We evaluated the effect of genotype and temperature on male unreduced gamete formation in Brassica allotetraploids and their interspecific hybrids. The frequency of unreduced gametes post-meiosis was estimated in sporads from the frequency of dyads or giant tetrads, and in pollen from the frequency of viable giant pollen compared with viable normal pollen. Giant tetrads were twice the volume of normal tetrads, and presumably resulted from pre-meiotic doubling of chromosome number. Giant pollen was defined as pollen with more than 1.5 × normal diameter, under the assumption that the doubling of DNA content in unreduced gametes would approximately double the pollen cell volume. The effect of genotype was assessed in five B. napus, two B. carinata and one B. juncea parents and in 13 interspecific hybrid combinations. The effect of temperature was assessed in a subset of genotypes in hot (day/night 30°C/20°C), warm (25°C/15°C), cool (18°C/13°C) and cold (10°C/5°C) treatments.ResultsBased on estimates at the sporad stage, some interspecific hybrid genotypes produced unreduced gametes (range 0.06 to 3.29%) at more than an order of magnitude higher frequency than in the parents (range 0.00% to 0.11%). In nine hybrids that produced viable mature pollen, the frequency of viable giant pollen (range 0.2% to 33.5%) was much greater than in the parents (range 0.0% to 0.4%). Giant pollen, most likely formed from unreduced gametes, was more viable than normal pollen in hybrids. Two B. napus × B. carinata hybrids produced 9% and 23% unreduced gametes based on post-meiotic sporad observations in the cold temperature treatment, which was more than two orders of magnitude higher than in the parents.ConclusionsThese results demonstrate that sources of unreduced gametes, required for the triploid bridge hypothesis of allopolyploid evolution, are readily available in some Brassica interspecific hybrid genotypes, especially at cold temperatures.

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Twinned microspore-derived embryos of canola (Brassica napus L.) are genetically identical

Cited by 17 publications

References 13 publications

Centromere Locations inBrassicaA and C Genomes Revealed Through Half-Tetrad Analysis

Centromere Locations inBrassicaA and C Genomes Revealed Through Half-Tetrad Analysis

Quantitative Trait Loci for Thermal Time to Flowering and Photoperiod Responsiveness Discovered in Summer Annual-Type Brassica napus L

Production of viable male unreduced gametes in Brassica interspecific hybrids is genotype specific and stimulated by cold temperatures

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