Analysis of the meiosis in the F-1 hybrids of Longiflorum x Asiatic (LA) of lilies (Lilium) using genomic in situ hybridization
Zhou, S.J. ; Ramanna, M.S. ; Visser, R.G.F. ; Tuyl, J.M. van - \ 2008
Journal of Genetics and Genomics 35 (2008)11. - ISSN 1673-8527 - p. 687 - 695.
intergenomic recombination - interspecific hybrids - parental genomes - allium-roylei - bc2 progenies - lily hybrids - gish - chromosomes - fistulosum - identification
Longiflorum and Asiatic lilies of the genus Lilium of the family Liliaceae are two important groups of modem lily cultivars. One of the main trends of lily breeding is to realize introgression between these groups. With cut style pollination and embryo rescue, distant hybrids between the two groups have been obtained. However, the F-1 hybrids are highly sterile or some of them could produce a small number of 2n gametes, and their BC1 progenies are usually triploids. Dutch lily breeders have selected many cultivars from these BC1 progenies based on their variation. It is presumably suggested that such variation could be caused by intergenomic recombination and abnormal meiosis during gamete formation in F-1 hybrids of Longiflorum, x Asiatic (LA) hybrids in Lilium. Therefore, the meiotic process of ten F-1 LA hybrids was cytologically investigated using genomic in situ hybridization and traditional cytological methods in the present research. The results showed that: at metaphase I, the homoeologous chromosome pairing among different F-1 hybrids ranged from 2.0 to 11.4 bivalents formed by homoeologous chromosomes per pollen mother cell (PMC), and very few multivalents, and even very few bivalents were formed by two chromosomes within one genome rather than homoeologous chromosomes in some PMCs; at anaphase I, all bivalents were disjoined and most univalents were divided. Both the disjoined bivalents (half-bivalents) and the divided univalents (sister chromatids) moved to the opposite poles, and then formed two groups of chromosomes; because the two resulting half-bivalents retained their axes in the cell undisturbed, many crossover types, including single crossovers, three strand double crossovers, four strand double crossovers, four strand triple crossovers, and four strand multiple crossovers between the non-sister chromatids in the tetrads of bivalents, were clearly inferred by analyzing the breakpoints on the disjoined bivalents. The present investigation not only explained the reason for sterility of the F-1 LA hybrids and the variation of their BC1 progenies, but also provided a new method to analyze crossover types in other F-1 interspecific hybrids as well.
Genome composition of triploid lily cultivars derived from sexual polyploidization of Longiflorum x Asiatic hybrids (Lilium)
Shujun Zhou, ; Ramanna, M.S. ; Visser, R.G.F. ; Tuyl, J.M. van - \ 2008
Euphytica 160 (2008)2. - ISSN 0014-2336 - p. 207 - 215.
in-situ hybridization - interspecific hybrids - aegilops-squarrosa - alstroemeria - gish - recombination - introgression - restitution - mechanisms - progenies
About 19 cultivars, which had originated from backcrosses between F1 LA (Longiflorum × Asiatic) hybrids (2n = 2x = 24) as female parents and Asiatic cultivars as male parents (2n = 2x = 24), were analyzed with genomic in situ hybridization. 17 of them were triploid (2n = 3x = 36), and two aneuploid (2n = 3x + 1 = 37). The triploid cultivars had resulted from the functional 2n eggs produced by the female parents (F1 hybrids) because first division restitution (FDR) occurred in their meiosis during megasporogenesis. Similarly, the aneuploid cultivars had originated from viable 2n + 1 eggs. The extra chromosome in cultivar 041555 or 041572 resulted from one univalent or one half-bivalent which might have lagged behind when the sister chromatids of the other univalents and half-bivalents were segregating during the FDR process in their LA hybrid parents, respectively. That the majority of cultivars possessed recombinant chromosomes showed that intergenomic recombination might play an important role during the selection of the cultivars directly from BC1 progenies. That five cultivars of the 15 recombinant cultivars only had reciprocal recombinant chromosomes and 10 cultivars had non-reciprocal recombinant chromosomes indicates that the latter are more important. Because 9 of the 10 non-reciprocal recombinant cultivars possessed substitutions for recombinant segments, it also indicated that such substitutions could be an important source for the genetic variation in the sexual triploid BC1 progenies. In such cases there was a potential for the expression of the recessive genes of the backcross parent in a nulliplex (aaa) condition in the substituted segments. Genetic variation resulting from such nulliplex loci might have played a role in the selection of some of the cultivars.
Nitrous oxide N2O incudes 2n gametes in sterile F1 hybrids of Oriental x Asiatic lilies (Lilium) and leads to intergenomic recombination
Barba Gonzalez, R. ; Miller, C.T. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2006
Euphytica 148 (2006)3. - ISSN 0014-2336 - p. 303 - 309.
in-situ hybridization - sexual polyploidization - interspecific hybrids - aneuploids - gish
Eight different genotypes of the F1 hybrids between Oriental × Asiatic lily (Lilium) hybrids (2n = 2x = 24) were treated with nitrous oxide (N2O) gas under pressure for 24 and 48 hours. At the time of treatment, all plants possessed early meiotic stages in the anthers of the oldest flower buds. The mature flowers from treated plants were monitored for fertility through pollen germination in vitro as well as by using them in crosses with diploid Asiatic hybrids (2n = 2x = 24) both as male and female parents. In five out of the eight genotypes of OA hybrids there was evidence for the production of 2n pollen which germinated in vitro from either one or both treatments. The 2n pollen from three genotypes was successfully used in crosses. In two cases, the treated plants were successfully used as female parents which indicated the formation of 2n (or 2x) egg cells. From an analysis of 41 sexual polyploid progenies obtained from N2O treated plants it was shown that they were all euploids consisting of 34 triploids (2n = 3x = 36) and seven tetraploids (2n = 4x = 48). A detailed cytological analysis of 12 progeny plants through genomic in situ hybridization (GISH) proved that N2O had induced first division restitution gametes in most cases and in two cases they produced gametes through indeterminate meiotic restitution. There was evidence for intergenomic recombination in three cases.
Meiotic polyploidization with homoeologous recombination induced by caffeine treatment in interspecific lily hybrids
Lim, K.B. ; Barba Gonzalez, R. ; Shujun Zhou, ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2005
Korean Journal of Genetics 27 (2005)3. - ISSN 0254-5934 - p. 219 - 226.
lilium hybrids - bc2 progenies - restitution - cytokinesis - gish
Caffeine solution was injected into the flower bud to recover F, fertility of the intersectional diploid Lilium species hybrid (2n=2x=24). 0.3% of caffeine solution was the most effective concentration to produce fertile 2n-gametes. The male and female gametes had a range of fertility following caffeine injection in relation to the different sizes of flower buds. The gametes from the treated OA-hybrids showed to be fertile. They were crossed both as male and female parents to the Asiatics, and produced 279 BC, progeny plants. Flowcytometric and chromosomal observation confirmed that all progenies were triploid (2n=3x=36), indicating that the 2n-gametes from the OA-hybrid were functional following caffeine treatment. There was no homoeologous recombination between parental species in the progeny derived from male gametes of the OA-hybrid. However, three plants originating from the female gametes showed homoeologous recombination between Oriental and Asiatic genomes. The functional female gametes were produced when treated at the range of 20-23mm and 34-37mm of flower bud length. Based on the chromosome constitution of the triploid BC1 progenies, it was concluded that FDR 2n-gamete was functional and homoeologous recombination had occurred during the origin of 2n gametes.
Occurrence of 2n gametes in the F1 hybrids of Oriental x Asiatic lilies (Lilium): Relevance to intergenomic recombination and backcrossing
Barba Gonzalez, R. ; Lim, K.B. ; Ramanna, M.S. ; Visser, R.G.F. ; Tuyl, J.M. van - \ 2005
Euphytica 143 (2005)1-2. - ISSN 0014-2336 - p. 67 - 73.
in-situ hybridization - aegilops-squarrosa - sexual polyploidization - interspecific hybrids - restitution - mechanisms - crosses - gish - rye
Cytological modes of the origin of 2n gametes were investigated in six different genotypes of F1 hybrids between Oriental and Asiatic (OA) lilies (Lilium, 2n = 2x = 24). Chromosome pairing between the parental genomes was very low, the average frequency range from 0.3 to 1.2 bivalents per cell among the genotypes. Within a genotype the frequency of bivalents varied from 0 to 6 in some cases. The normally occurring haploid pollen grains were totally sterile. In contrast, in different genotypes, variable percentages of 2n pollen were found and shown to be fertile as estimated from pollen germination. A cytological analysis of Metaphase I and subsequent stages of meiosis using genomic in situ hybridization (GISH) revealed that there was intergenomic recombination between the alien genomes. Following Metaphase I stage, three different types of abnormal cytological events led to the formation of 2n pollen: (i) Post-Metaphase I division (PMI), (ii) Post-Metaphase II division (PMII) and (iii) Asymmetric Cytokinesis of the pollen mother cell followed by chromosome division. All three cytological events led to first division restitution (FDR) gametes. Based on in vitro pollen germination it was proved for two genotypes that 2n pollen was viable only during the first day of anthesis. It was possible to use 2n pollen successfully for backcrossing. Implications of 2n pollen for intergenomic recombination in BC1 progenies are discussed
Occurrence of SDR 2N-gametes in Lilium hybrids
Lim, K.B. ; Shen, T.M. ; Barba Gonzalez, R. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2004
Breeding Science 54 (2004)1. - ISSN 1344-7610 - p. 13 - 18.
interspecific hybrids - bc2 progenies - potato - mutants - desynapsis - fertility - crosses - pollen - gish
The mechanism of SDR 2n-pollen formation was analyzed in two intra-sectional diploid (2n = 2x = 24) Lilium hybrids (Enchantment x L. pumilum). Variable frequencies of 2n-pollen were found. Meiotic analysis indicated that the intra-sectional hybrids showed perfect chromosome pairing in most cases at metaphase I and normal anaphase I movement of pollen mother cells (PMCs), but produced 2n-pollen by second division restitution (SDR). A high bivalent formation (11.9II and 11.8II, respectively) at metaphase 1, irregular meiotic division such as unbalanced chromosome separation and chromatic fragmentation resulted yet in acceptable pollen fertility for cross-pollination. The hybrids were fertile, and when used as male parents, offspring could tie generated. The significance of the occurrence of 2n-pollen for the breeding of lilies was analyzed.