The effect of polyploidy and hybridity on seed size in crosses betweenBrassica chinensis, B. carinata, amphidiploidB. chinensis-carinata and auto-tetraploidB. chinensis

Howard, H. W.

doi:10.1007/bf02982749

Cited by 38 publications

(19 citation statements)

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“…We found that results from FISH in combination with molecular karyotyping were highly effective for determining detailed chromosome complements in cytogenetically complex hybrids, as has also been demonstrated in oats (Jellen et al 1994), banana, andsugarcane (D'Hont 2005). This analysis highlighted the dangers of using simple chromosome counts to assess meiotic stability of Brassica allohexaploids, as has been done in other studies (e.g., Howard 1942;Tian et al 2010). In the future, molecular karyotyping with molecular cytogenetics may allow identification of genotypic and species-specific variability for meiotic stability in higher-ploidy Brassica.…”

Section: Discussionmentioning

confidence: 82%

“…However, mixed results have been reported for success of these synthetic allohexaploid Brassica. Howard (1942) reported relatively high fertility over several generations of self-pollination of 2n = AABBCC plants derived from the cross B. rapa 3 B. carinata. However, Iwasa (1964) found poor meiotic stability in the same species cross that failed to improve even up to the F 5 selfing generation, resulting in loss of fertility and hence usefulness of this crop.…”

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confidence: 99%

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The Fate of Chromosomes and Alleles in an AllohexaploidBrassicaPopulation

et al. 2014

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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 highthroughput 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 3 B. carinata) 3 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 F 2 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 F 2 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.T HE Brassica genus contains the largest number of cultivated crop species of any plant genus (Dixon 2007). Six major crop species are B. rapa (Chinese cabbage, turnip), B. oleracea (cabbage, cauliflower, broccoli), B. nigra (black mustard), B. napus (canola, rapeseed), B. juncea (Indian mustard, leaf mustard), and B. carinata (Ethiopian mustard). These six species share a unique genomic relationship: progenitor diploid species B. rapa (2n = AA), B. oleracea (2n = CC), and B. nigra (2n = BB) gave rise to the allotetraploid species B. juncea (2n = AABB), B. napus (2n = AACC), and B. carinata (2n = BBCC) through pairwise crosses (Morinaga 1934;U 1935). However, despite the fact that each pair of genomes coexists in an allotetraploid species, no naturally occurring allohexaploid species (2n = AABBCC) exists. In general, interspecific hybridization and polyploidy in plants are potent evolutionary mechanisms, allowing formation of new species with adaptation to a wider range of climatic conditions and greater "hybrid vigor" than their progenitor species (Otto and Whitton 2000;Leitch and Leitch 2008). Hence, production of an artificial allohexaploid in the agriculturally important Brassica genus could potentially give rise to new crop types with greater intersubgenomic heterosis ) and tolerance of a wider range of environmental conditions than preexisting Brassica crops (Chen et al. 2011).

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Section: Discussionmentioning

confidence: 82%

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confidence: 99%

The Fate of Chromosomes and Alleles in an AllohexaploidBrassicaPopulation

et al. 2014

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“…that the difference between the cross and its reciprocal is mainly shown in a difference in development of endosperm, which is different in constitution in the two cases; and he also emphasizes that this type of result is not necessarily correlated with a difference in chromosome number between the species concerned. Howard (1942), in analysing the seeds of crosses between a number of diploid, autotetraploid and allotetraploid species of Brassica, finds that in most cases the results follow Watkins's rule (quoted above), but suggests that some allotetraploid species may have evolved so as to have a 'diploid physiology', i.e. they will produce normal seeds when crossed in either direction with a diploid species.…”

Section: Discussionmentioning

confidence: 99%

Studies in British Primulas

Valentine

1947

New Phytologist

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“…The A, B and C genomes are able to co-exist in allopolyploids, as demonstrated by regular diploid behaviour in the three allotetraploid species with 2n = AABB, AACC and BBCC. Contrary to the initial doubt that an allohexaploid Brassica could establish and maintain meiotic stability (Howard 1942;Iwasa 1964), recent evidence suggests that regular diploid behaviour in meiosis can be selected during generations of selfing in allohexaploid Brassica hybrids (Tian et al 2010). Regular diploid behaviour can also be selected in progeny of resynthesised allotetraploids B. juncea, B. napus and B. carinata which are unstable in the original hybrids (Prakash et al 1999).…”

Section: Introductionmentioning

confidence: 84%

A new method for producing allohexaploid Brassica through unreduced gametes

et al. 2011

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We trialled a two-step method of producing allohexaploid Brassica with three genomes (A, B, and C) derived from pair-wise crossing among three allotetraploid Brassica species. In the first step, the three allotetraploid Brassica species (Brassica juncea, A ) were intercrossed in pairs to produce unbalanced trigenomic hybrids: A . In the second step, these hybrids were crossed with the complementary allotetraploid parent, that is, A

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The effect of polyploidy and hybridity on seed size in crosses betweenBrassica chinensis, B. carinata, amphidiploidB. chinensis-carinata and auto-tetraploidB. chinensis

Cited by 38 publications

References 11 publications

The Fate of Chromosomes and Alleles in an AllohexaploidBrassicaPopulation

The Fate of Chromosomes and Alleles in an AllohexaploidBrassicaPopulation

Studies in British Primulas

A new method for producing allohexaploid Brassica through unreduced gametes

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