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

Chapter 1quite divergent with various chromosome rearrangements. These structure variation can causeabnormal segregation and/or chromosome bridges during meiosis. Gametes from thosemeiotic divisions possess duplication/deletion and are generally sterile.Anaphase I bridging has been well documented in a few interspecific hybrids. Togetherwith univalents and multivalents, the presence of anaphase bridges is a relatively normalphenomenon in hybrids, like Vigna umbellate × V. minima (Gopinathan and Babu 1986),Pinus hybrids (Saylor and Smith 1966), Chorthippus hybrids (Lewis and John 1963), Alliumhybrids (McCollum 1974), Nicotiana tabacum × N. glauca (Trojak-Goluch and Berbec 2003),Phaseolus vulgaris × P. coccineus (Cheng et al. 1981), Elymus farctus × E. repens (Heneen1963), Guizotia hybrids (Dagne 1994) and so on. The production of bridges during meiosishad once exclusively explained as the presence of chromosome rearrangements like inversion(McClintock 1931). Later on, another cause-U-type exchanges, became an alternativeexplanation for the production of bridges (Couzin and Fox 1973; Haga 1953; Jones andBrumpton 1971; Jones 1969; Karp and Jones 1983; Lewis and John 1963; Newman 1967;Rees and Thompson 1955). According to the meiotic configuration, these two causes can bedistinguished. Moreover, molecular biology has revealed that two different mechanisms aremainly involved in the repair of double strand breaks (DSBs) in mitosis-homologousrecombination (HR) and nonhomologous end joining (NHEJ). Crossovers have beenexplained as a process of DSBs and the repair with HR (Puchta 2005; Schwacha and Kleckner1995; Szostak et al. 1983), whereas the relationship between U-type exchanges and NHEJ isnot clear yet.Scope and aim of the thesisIn this research, an attempt will be made to investigate the following four topics:1. to analyze the genome composition of mitotic and meiotic polyploidized neopolyploidsof lily hybrids, and detect, if any, intergenomic chromosome rearrangements as a result of theso-called genomic shock.2. to elucidate the meiosis process, especially the crossing-over events happened atanaphase I of interspecific hybrids of LA lilies and the gamete formation.3. to detect the abnormalities of meiosis, including the failure of chromosome pairing,abnormal association and segregation, and any other chromosome rearrangements duringmeiosis of the interspecific hybrids of LA lilies.4. to trace the origins and behavior of the aberrant small chromosomes occurring in thebackcrossing progenies,.With those above mentioned purposes, interspecific hybrids were made and distantlyrelated hybrids between Longiflorum and Asiatic cultivars became available. Then the12