A molecular cytogenetic analysis of chromosome behavior in Lilium ...

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Chapter 2AbstractTwo types of newly induced polyploids (neopolyploids) of Lilium hybrids were monitored forthe occurrence of chromosomal rearrangements through Genomic in situ Hybridization (GISH)technique. One of the populations was obtained through crossing an allotriploid Longiflorum× Oriental hybrid (LLO) and an allotetraploid Longiflorum × Trumpet hybrid (LLTT) both ofwhich were derived from somatic chromosome doubling. The other type of allopolyploidpopulation was derived from meiotic chromosome doubling in which numerically unreduced(2n) gametes from two different interspecific hybrids, viz., Longiflorum × Asiatic (LA) andOriental × Asiatic (OA), were used to get backcross (BC) progeny with the Asiatic parents.GISH clearly discriminated the three constituent genomes (L, T and O) in the complements ofthe progeny obtained from mitotic chromosome doubling. A total of 26 genotypes wereanalyzed from this population and there was no evidence for any chromosomalrearrangements. However, in the case of meiotically doubled allopolyploid progenyconsiderable frequencies of chromosomal rearrangements were observed through GISH. Theso-called chromosomal rearrangements in meiotic polyploids are the result of homoeologousrecombination rather than “translocations”. Evidence for the occurrence of meioticrecombination in the LA hybrids has been confirmed with GISH on meiotic chromosomes.Thus, there was evidence that neopolyploids of Lilium hybrids did not possess any noticeablechromosome rearrangements.Keywords: Lilium; polyploids; genomic in situ hybridization (GISH); homoeologousrecombination16
Chromosome rearrangements in Lilium hybridsIntroductionThe occurrence of profound changes in newly synthesized polyploids (neopolyploids) hasbeen recognized for a long time in many plant species (see review, Ramsey and Schemske2002). Such changes occur in both auto- and allopolyploids and exhibit meiotic complexityincluding multivalent pairing, multisomic inheritance and the production of unbalancedgametes. More recent investigations have indicated that extensive “chromosomalrearrangements” commonly occur in neopolyploids of some plant species, the chromosomalrearrangements in these cases include translocations, duplications and deletions. Someexamples of neopolyploids that have been analysed in detail are: Brassica species hybrids(Nicolas et al. 2007; Osborn et al. 2003; Song et al. 1995; Udall et al. 2005) and hybridsbetween wheat and its related species (David et al. 2004; Feldman et al. 1997; Zhang et al.2008). The implications of such chromosomal rearrangements for the evolution of polyploidshave been reviewed (Leitch and Bennett 1997, 2004; Wendel 2000). Moreover, if extensivechromosomal rearrangements do occur, they might have implications for the speciation ofneopolyploids.Apart from other observations on neopolyploids, molecular cytogenetic analyses usinggenomic in situ hybridization (GISH) technique on some of the allopolyploid crops and theirrelatives have revealed the occurrence of several intergenomic translocations in theircomplements. For example, in tobacco (Nicotiana tabaccum L.) nine intergenomictranslocations have been detected (Kenton et al. 1993); in Avena maroccana Gand. five and incultivated oat (A. sativa L.) as many as 18 intergenomic translocations have been identified(Chen and Armstrong 1994; Jellen et al. 1994). It is concluded that such translocations mayoccur following polyploid formation (Leitch and Bennett 1997). In the case of tobacco andwheat there is convincing evidence that these translocations involve nonhomologouschromosomes of different genomes (Parokonny and Kenton 1995; Zhang et al. 2008).Unlike translocations that involve nonhomologous chromosomes, the occurrence of socalled“homeologous translocations” have been reported in the case of neopolyploids ofBrassica napus L. (2n = 4x = 38) (Nicolas et al. 2007; Osborn et al. 2003; Udall et al. 2005).The neopolyploids used in these analyses were produced by crossing dihaploids of B. napus(2n = 2x = 19) as female parents with tetraploid male parents. The progenies in these casesoriginated through the functioning of 2n eggs from the dihaploids and 2x pollen from theeuploid parent. As expected, the progenies were tetraploid. By genotyping theseneopolyploids with molecular markers, extensive chromosomal rearrangements that included“homeologous nonreciprocal translocations (HNRT), duplications and deletions wereobserved (Nicolas et al. 2007). The origin of chromosomal rearrangements was explained asdue to recombination between the two distinct but related genomes of B. napus (AACC), i.e.,A = B. rapa (x = 10) and C = B. oleracea (x = 9) during the formation of 2n eggs in thedihaploids. Thus, based on the examples of wheat and tobacco on the one hand and B. napus17
Page 3 and 4: A molecular cytogenetic analysis of
Page 5: Table of ContentsChapter 1General I
Page 8 and 9: Chapter 1LilyLilies belong to genus
Page 10 and 11: Chapter 1counterparts (Finnegan 200
Page 12 and 13: Chapter 1renewed interest in detect
Page 14 and 15: Chapter 1recombination, mechanisms
Page 16 and 17: Chapter 1is only an equational segr
Page 18 and 19: Chapter 1quite divergent with vario
Page 21: Chapter 2An assessment of chromosom
Page 25 and 26: Chromosome rearrangements in Lilium
Page 37 and 38: Chapter 3Elucidation of intergenomi
Page 39 and 40: Intergenomic recombination and chro
Page 49: Intergenomic recombination and chro
Page 52 and 53: Chapter 4AbstractMeiotic abnormalit
Page 54 and 55: Chapter 4There are some criteria to
Page 56 and 57: Chapter 4FISH experiments were perf
Page 58 and 59: Chapter 4was apparently shorter, wi
Page 60 and 61: Chapter 4bridges is explained as U-
Page 62 and 63: Chapter 4of the sexual polyploidize
Page 64 and 65: Chapter 4fragment have the same len
Page 66 and 67: Chapter 5AbstractSupernumerary (B)
Page 68 and 69: Chapter 5their origin, the structur
Page 70 and 71: Chapter 5Fig. 5.1. Discovery of B c
Page 72 and 73:
Chapter 5In order to investigate th
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Chapter 5Centric breakage and fusio
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Chapter 5It has not, however, been
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Chapter 6The results presented in t
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Chapter 6model for molecular cytoge
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Chapter 6Fig. 6.2. The meiosis proc
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Chapter 6over events during FDR mei
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Chapter 6been detected with GISH an
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Chapter 6Another feature caused by
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ReferencesAbe, H.A., Nakano, M.N.,
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ReferencesChen, Q., and Armstrong,
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ReferencesHartlerode, A.J., and Scu
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ReferencesLarson, S.R., Kishii, M.,
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ReferencesMcClintock, B. 1931. Cyto
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ReferencesRai, R., Zheng, H., He, H
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ReferencesStewart, R.N. 1947. The m
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ReferencesZhang, L., Pickering, R.,
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Summarychromosome rearrangements. T
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SamenvattingLelie (Lilium) is in de
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Samenvattingaantal 35 met daarnaast
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摘要百合系百合科百
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Acknowledgements淡看世事去
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Curriculum VitaeSonglin Xie was bor
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Education Statement of the Graduate
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