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Using 23 F1 hybrids, 14 BC1 and 32 BC2 progenies, the genome composition of Darwin hybrid tulips was analysed through genomic in situ hybridisation (GISH) of somatic chromosomes. All plants were diploids (2n = 2x = 24) with the exception of one tetraploid BC1 (2n = 4x = 48) and one aneuploid BC2 (2n = 2x + 1 = 25) hybrid. Morphometric analysis in F1 hybrids revealed a difference in the total length of chromosomes representing genomes of T. gesneriana and T. fosteriana, where the percentage of each genome equaled 55.18 ± 0.8 and 44.92 ± 0.6% respectively. GISH distinguished chromosomes from both parent genomes although there was a lack of consistent chromosome labelling in some cases. In both T. gesneriana and T. fosteriana chromosomes some segments of heterochromatin in the telomeric and intercalary regions exhibited a higher intensity of fluorescence. In situ hybridisation with 5S rDNA and 45S rDNA probes to metaphase chromosomes of F1 hybrids showed that these regions are rich in rDNA. A notable feature was that, despite genome differences, there was a considerable amount of intergenomic recombination between the parental chromosomes of the two species as estimated in both BC1 and BC2 offspring. The number of recombinant chromosomes ranged from 3 to 8 in BC1 and from 1 to 7 in BC2 progenies. All recombinant chromosomes possessed mostly a single recombinant segment derived from either a single crossover event or in a few cases double crossover events. This explains the fact that, unlike the situation in most F1 hybrids of other plant species, certain genotypes of Darwin hybrid tulips behave like normal diploid plants producing haploid gametes and give rise to mostly diploid sporophytes.

Sexual polyploids were induced in diploid (2n = 2x = 24) interspecific F1 hybrids of Longiflorum × Asiatic (LA) and Oriental × Asiatic (OA) Lilium hybrids by backcrossing to Asiatic (AA) parents as well as by sib-mating of the F1 LA hybrids. A majority of the BC1 progenies were triploid and the progenies from sib-mating were tetraploid or near tetraploids. Genomic in situ hybridization (GISH) technique was applied to assess the intergenomic recombination in the BC1 populations of LA and OA hybrids obtained after unilateral sexual polyploidization. A total of 63 LA (LA × AA and AA × LA) and 53 OA hybrids were analysed. LA hybrids were originated through the functioning of 2n gametes either as 2n eggs or 2n pollen while those of OA hybrids originated through functional 2n pollen of diploid OA genotype. In both type of crosses, a majority of the progenies had originated through First Division Restitution (FDR) mechanism of functional 2n gamete either with or without a cross over. However, there were nine LA- and four OA-genotypes where Indeterminate Meiotic Restitution (IMR) was the mechanism of 2n gamete formation. Based on GISH, total amount of introgression of Longiflorum and Oriental genome into Asiatic genome was determined. Most of the BC progenies exhibited recombination and the amount of recombination was higher in LA hybrids as compared to OA hybrids. Intergenomic recombination was also determined cytologically in the 16 plants of sib-mated LA hybrids where both parents had contributed 2n gametes. Based on these results the nature of interspecific lily hybrids obtained from uni- and bilateral sexual polyploidization leading to allotriploid and allotetraploid formation is discussed in the context of introgression and intergenomic recombination

Interspecific hybridization of various tuberous Begonia species hybrids with Begonia socotrana results in so-called 'Elatior'-begonias hybrids (B. x hiemalis Fotsch). In our study, genomic in situ hybridization (GISH) has been employed to assess the genome composition in eleven 'Elatior'-begonias hybrids and their ancestor genotypes. Genomic DNA of tuberous Begonia was sonicated to 1-10-kb fragments, labelled by nick translation with digoxigenin-11-dUTP and used as a probe whereas B. socotrana DNA was autoclaved to 100 bp fragments and used as block. The genome of tuberous Begonia was clearly pronounced in 'Elatior'-begonias when the probe concentration was similar to 3.75 ng/mu l (150 ng/slide), with 30 times the excess of B. socotrana blocking DNA and stringency of post hybridization washings at 73% (0.1x SSC at 42A degrees C). In 'Elatior'-begonias hybrids GISH distinguished two groups comprising short (0.6-1.03 mu m in length) and relatively longer chromosomes (1.87-3.88 mu m) which represent B. socotrana and tuberous Begonia genomes, respectively. The number of chromosomes derived from tuberous Begonia ranged from 14 to 56 and for B. socotrana from 7 to 28 which suggest the presence of different ploidy levels in analyzed 'Elatior'-begonia hybrids. Intergenomic recombination has not been detected through GISH in hybrids analyzed. Genomic in situ hybridization turned out to be useful to identify the genome constitution of 'Elatior'-begonia hybrids and thus gain an insight into the origins of these cultivars. This knowledge on the ploidy level and genome composition is essential for further progress in breeding Begonias.

Ploidy level and intergenomic recombination was studied in interspecific hybrids between Longiflorum × Asiatic lilies (LA hybrid) backcross to Asiatic parents in order to assess the possibility for analytic breeding in lily. By backcrossing the diploid (2n = 2x = 24) F1 interspecific hybrid between Longiflorum × Asiatic lilies to Asiatic parents, 104 BC1 progeny plants were produced. Among these, there were 27 diploids, 73 triploids (2n = 2x = 36) and 4 aneuploids (2x ¿ 1, 2x + 2 or 2x + 3). In addition, by backcrossing triploid BC1 (LAA) plants to diploid Asiatic parents in 2x ¿ 3x and reciprocal combinations, 14 diploid BC2 progenies were produced. Genomic in situ hybridization (GISH) was performed to study the intergenomic recombination and karyotype composition. GISH indicated extensive intergenomic recombination among the chromosomes in LA hybrids. A large number of Longiflorum chromosomes were transmitted to the BC1 progenies from LA hybrids. However, very few Longiflorum chromosomes were transmitted from the BC1 triploid (LAA) plants to the BC2 progenies. The occurrence of diploid plants in the BC progenies of LA hybrids has opened the prospects of analytic breeding in lilies. In this approach, the selection of superior genotypes can be carried out at the diploid level and polyploid forms are synthesized from superior diploid parents. The advantages of analytic breeding are evident: (a) a maximum level of heterozygosity can be attained in the synthetic polyploids and (b) introgression can be achieved with a minimum of linkage drag. Based on GISH results the potential application of analytic breeding in lily allopolyploids has been discussed

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.

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.

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.

Producing somatic fusion hybrids between distantly related non-crossable taxa opened the possibilities for the introgression of useful genes or chromosomes from various species to cultivated crops. The molecular biological techniques like genome analysis by molecular markers, amplified fragment length polymorphism (AFLP) restriction fragment length polymorphism (RFLP) and in situ hybridization (ISH) have enabled the identification of genomes and individual chromosomes with great accuracy and efficiency. These techniques have surpassed all the difficulties that were faced in conventional breeding or classical cytogenetics in identification of desirable chromosomes and genes.The main aims of the present series of investigation, were the following; a) to complete the series of monosomic alien tomato addition lines by identifying the five chromosomes (3,5,7,9,11) that were not identified in a previous investigation; b) to gain more insight into the possible phenotype in a nullisomic potato background of a known genetic locus (amylose-free) present on one of the monosomic addition chromosome; c) to explore the possibilities of increasing the prospects of intergenomic recombination between potato and tomato chromosomes by crossing with a bridge species and d) to test whether homoeologous recombination segments can be cytologically detected, i.e., through GISH, so that the alien segments can be monitored in individual potato chromosomes for the purpose of introgression of tomato encoded traits in potato.For this purpose, basically a combination of RFLP and GISH analyses was used to identify and prove the presence of an alien tomato chromosome in potato. Where all the monosomic addition lines were identified, an additional disomic line was also identified for chromosome 11 by GISH analysis. Meiotic analysis of this disomic addition had a tendency for precocious separation of the paired homologous alien chromosomes at metaphase I and anaphase I stages. There is no definite a

This thesis describes the results of a molecular cytogenetic investigation of the process of introgression in Alstroemeria . The aim of this study was to transfer chromosomes or genes from one Alstroemeria species into another. For this, two distantly related species, A. aurea and A. inodora , were hybridized and the resulting hybrids were further backcrossed with the species A. inodora . To monitor the process of introgression accurately it was necessary to identify the individual chromosomes of both parental species.In addition to classical karyotyping, reliable criteria for unequivocal identification of all individual somatic chromosomes of the species A. aurea and A. inodora have been developed by applying fluorescence in situ hybridization (FISH) with tandemly repeated DNA probes (Chapter 2). Four probes, two species specific, A001-I (for A. aurea ) and D32-13 (for A. inodora ), and two ribosomal rDNA repeats, pTa71 (18S-25S) and pTa794 (5S), revealed specific banding patterns per chromosome, enabling identification of all individual chromosomes. In contrast to most plant species, both Alstroemeria species contained a large number of rDNA sites (per haploid genome: 20 in A. aurea and 16 in A. inodora ). Remarkably, the physical location of the rDNA sites varied greatly between the two species; only a few were found at similar positions.Besides identification of somatic chromosomes, FISH with the species specific probes was used for the identification of meiotic chromosomes to accurately determine the extent of homoeologous association in the diploid parental hybrid. Multicolour FISH experiments revealed a large number of bivalents per Metaphase I cell (average 6.7 bivalents per MI) of the hybrid A. aurea x A. inodora , which indicated that homoeologous recombination occurs frequently in the hybrid.Successful backcrossing of the highly sterile distant hybrid A. aurea x A. inodora with its parent A. inodora resulted in a small number of first generation backcross