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

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Chapter 2chromosomes were put into sequence according to the decreasing short arm length (Khan et al.2009a; Lim et al. 2001b; Stewart 1947), and in order to identify the chromosome number ineach genome, chromosome length, arm ratio, the centromere index (short arm length/ longarm length +short arm length), and relative chromosome length index (individualchromosome length/total length of a set of chromosomes) were used as identification tools(Barthes and Ricroch 2001).Statistical analysisA Chi-square (χ 2 ) test was used to determine whether observed reciprocal and nonreciprocalproduct frequencies in the polyploids from meiotic chromosome doubling are significantlydifferent with expectations.ResultsBecause the progeny derived from LLO × LLTT crosses were expected to possesschromosomes from three different genomes (L, O and T), GISH with two probes was used todetect three types of chromosomes simultaneously in the complements (Fig. 2.1a). For theinterspecific F1 hybrids and meiotically doubled backcross progeny of LA and OA hybrids,only two genomes were involved and they were analysed through an one-probe GISHprocedure. The results of the two types of populations are described separately.Table 2.1. Genome composition of the progeny derived from crossing allotriploid (LLO) ×allotetraploid (LLTT) parents derived from somatic doubling determined through GISHCross Number of Number of Genome composition Number ofplants chromosomes L-genomeO-genomeT-genomerecombinantchromosomesLLO × LLTT 6 40 24 4 12 0LLO × LLTT 8 41 24 5 12 0LLO × LLTT 5 42 24 6 12 0LLO × LLTT 4 43 24 7 12 0LLO × LLTT 3 44 24 8 12 0Chromosome composition of progenies derived from somatic doublingThe progeny of LLO × LLTT cross were expected to be aneuploid, because LLO was anallotriploid and had contributed aneuploid gametes whereas euploid 2x gametes wereexpected to be functional from the LLTT parent. In all, 26 progeny were analysed throughGISH to assess their chromosome constitution (Table 2.1). As expected, all the genotypes ofthis population were aneuploid with chromosome numbers ranging from 40 to 44. A notablefeature was that the chromosomes of the three constituent genomes, viz., L, O and T wereclearly distinguishable in individual cells (Fig. 2.1a). Invariably, there were 24 chromosomes20
Chromosome rearrangements in Lilium hybridsof L genome and 12 of T genome. The number of chromosomes of O genome, however,varied from a minimum of four to a maximum of eight which was the cause of aneuploidy(Table 2.1). A significant feature was that in none of the analyzed 26 progeny there was anyevidence for the presence of chromosomal interchanges, either due to intergenomicrecombination or translocations. This was expected from the fact that a cursory examinationof the parents (viz., LLO and LLTT) had indicated the absence of any chromosomalrearrangements.Table 2.2. Statistics of genotype number, recombinant chromosomes, reciprocal and nonreciprocalproduct in the meiotic polyploidized progeny of LA × AA and AA × OA crossesGroupNumber ofNumber of reciprocalNumber of Recombinantnonreciprocalproductsplants chromosomesproductsfound/Expectedfound/ExpectedLA × AA 64 362 87/90.5 182/181AA × OA 36 131 28/32.75 77/65.5Chromosome composition of sexual polyploid progenies of LA and OA hybridsIn the case of BC1 progeny of LA and OA hybrids, 100 (64 + 36 respectively) genotypeswere analysed through GISH (Table 2.2). All of these progeny had originated through thefunctioning of 2n gametes from the F1 LA and OA hybrids. A common feature of thesesexual polyploid progeny was the occurrence of extensive homoeologous chromosomalexchanges due to intergenomic recombination (Fig. 2.1b; Table 2.2) In the backcross progeny,although the number of recombination sites was restricted to one or two in most cases, therewere instances in which seven to eight breakpoints per chromosome were present (Fig. 2.1d).The number of recombinant chromosomes varied from a single to as many as 20 per genotype.In all cases the recombinant chromosomes were identified and different types were indicatedas follows: In the case of BC1 progeny of LA hybrids, a chromosome with the centromere ofL and the recombinant segment of A was indicated as L/A and vice versa for its counterpart(i.e., A/L, see Fig. 2.1c). In the case of the progeny of OA hybrids, a chromosome with acentromere of O and a recombinant segment of A was indicated as O/A and vice versa for itscounterpart (i.e., A/O). The recombinant chromosomes were expected to segregate in theprogeny on the observation that almost all 2n gametes in interspecific hybrids had originatedthrough first division restitution (FDR) in which the sister chromatids of a recombinantchromosome randomly moved , as a rule, to opposite poles during restitution nucleusformation (Fig. 2.2). Thus, when the sister chromatids of a pair of homoeologouschromosomes with a crossover segregated during FDR, two alternative types of segregationswere expected: one in which two non-crossover and two crossover chromatids moved toopposite poles (Fig.2.2-I); and another in which only one of the crossover chromatid plus a21
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 and 22: Chapter 2An assessment of chromosom
Page 23 and 24: Chromosome rearrangements in Lilium
Page 25: 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
Page 74 and 75: Chapter 5Centric breakage and fusio
Page 76 and 77:
Chapter 5It has not, however, been
Page 78 and 79:
Chapter 6The results presented in t
Page 80 and 81:
Chapter 6model for molecular cytoge
Page 82 and 83:
Chapter 6Fig. 6.2. The meiosis proc
Page 84 and 85:
Chapter 6over events during FDR mei
Page 86 and 87:
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
Page 111 and 112:
SamenvattingLelie (Lilium) is in de
Page 113 and 114:
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
Page 119:
Curriculum VitaeSonglin Xie was bor
Page 123:
Education Statement of the Graduate
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