Karyotypic characterization of <Emphasis Type="Italic">Trachemys dorbigni</Emphasis> (Testudines: Emydidae) and <Emphasis Type="Italic">Chelonoidis (Geochelone) donosobarrosi</Emphasis> (Testudines: Testudinidae), two species of Cryptodiran turtles from Argentina

We describe for the first time the karyotypes of two species of Cryptodiran turtles from Argentina, namely, Trachemys dorbigni (Emydidae) and Chelonoidis (Geochelone) donosobarrosi (Testudinidae). The karyotype of T. dorbigni (2n = 50) consists of 13 pairs of macrochromosomes and 12 pairs of microchromosomes, whereas the karyotype of C. donosobarrosi (2n = 52) consists of 11 pairs of macrochromosomes and 15 pairs of microchromosomes. Fluorescence in situ hybridization (FISH) with a (TTAGGG)n telomeric probe showed that the chromosomes of these species have four telomeric signals, two at each end, indicating that none of the chromosomes of T. dorbigni and C. donosobarrosi are telocentric. The fact that no interstitial telomeric signals were observed after FISH, suggests that interstitial telomeric sequences did not have a major role in the chromosomal evolution of these species. Additional data will be needed to elucidate if interstitial telomeric sequences have a major role in the karyotypic evolution of Testudines.     

Karyological studies of some representatives of <Emphasis Type="Italic">Tanacetum</Emphasis> L. (Anthemideae-Asteraceae) from north-east Anatolia

The karyotypes of nine Tanacetum taxa distributed in north-east Anatolia, Turkey, were determined and evaluated by cluster analysis and principal-components analysis. Chromosome numbers were 2n = 2x = 18 (8 taxa) and 4x = 36 (1 taxon). Somatic chromosome numbers of two taxa and a new ploidy level in one taxon are reported for the first time. Karyotype analysis indicated that chromosomes of Tanacetum taxa have predominantly median centromeres. The taxa studied differed significantly in the size of the short arms and long arms, and the arm ratio of each pair of homologous chromosomes, indicating structural rearrangements of the chromosomes have been involved in diversification of the taxa. They were placed in 2A, 3A, and 2B of Stebbins’ karyotype classification, showing the presence of a primitive symmetrical karyotype in the genus. Several systematic and evolutionary aspects of the genus are discussed on the basis of karyological data.     

Cytological analysis of constitutive heterochromatin in two species of birds

Two species of birds, the myna (Acridotheres tristis L.) and the jungle babbler (Turdoides malcolmi Sykes), have been studied cytologically. Their modal diploid numbers are 78±2 and 68±2 respectively. In T. malcolmi the heterochromatin is located on the centromeres of all the macros and most of the microchromosomes, heterochromatin comprises predominantly GC-sequences and at least one pair of microchromosomes is responsible for nucleolus organization. The occasional occurrence of silver deposition on more than one pair of microchromosomes suggests the possibility that more than one pair of micros may be associated with the synthesis of rRNA. The heterochromatin in A. tristis is AT-rich and restricted to the macro-chromosomes, though most of the micros are also C-band positive; no particular chromosome stains with silver nitrate, though when interphase cells are stained with acridine orange the nucleolus is surrounded by brightly fluorescing chromatin. Apparently unlike other species, the microchromosomes in the myna do not harbour NORs.     

Molecular cytogenetic study on the ploidy status in Acipenser mikadoi

The ploidy status of Acipenser mikadoi was examined using nuclear DNA contents, karyotypes and fluorescence in situ hybridization (FISH) with 5.8S + 28S rDNA as a probe. In flow‐cytometrically sorted specimens with 8.2–9.1 pg DNA content per somatic cell, i.e. genetic diploid, the best informative metaphase with 268 chromosomes had 80 biarmed meta‐ or submetacentric (M or SM) chromosomes, 48 monoarmed telocentric (T) chromosomes and 140 microchromosomes. In genetic triploid specimens with 12.6–13.0 pg DNA content, the best informative metaphase with 402 chromosomes showed 120 biarmed M or SM, 72 monoarmed T chromosomes and 210 microchromosomes. The rDNA FISH detected a maximum 18 and 27 signals in the diploid and triploid A. miakdoi, respectively. The obtained findings thus corroborated a clear parallel between nuclear DNA contents and karyological or FISH profiles in the genetic diploid and triploid specimens, suggesting 1.5 times chromosome complements of diploid counterparts or three sets of homologues in the triploid sturgeons. Moreover, the estimated genome size and the observed molecular cytogenetic features in the diploid A. mikadoi strongly suggest that this species is a member of a functional tetraploid group recently proposed in the literature.     

Comparison of genomes of eight species of sections <Emphasis Type="Italic">Linum</Emphasis> and <Emphasis Type="Italic">Adenolinum</Emphasis> from the genus<Emphasis Type="Italic"> Linum</Emphasis> based on chromosome banding,molecular markers and RAPD analysis

Karyotypes of species sects. Linum and Adenolinum have been studied using C/DAPI-banding, Ag-NOR staining, FISH with 5S and 26S rDNA and RAPD analysis. C/DAPI-banding patterns enabled identification of all homologous chromosome pairs in the studied karyotypes. The revealed high similarity between species L. grandiflorum (2n = 16) and L. decumbens by chromosome and molecular markers proved their close genome relationship and identified the chromosome number in L. decumbens as 2n = 16. The similarity found for C/DAPI-banding patterns between species with the same chromosome numbers corresponds with the results obtained by RAPD-analysis, showing clusterization of 16-, 18- and 30-chromosome species into three separate groups. 5S rDNA and 26S rDNA were co-localized in NOR-chromosome 1 in the genomes of all species investigated. In 30-chromosome species, there were three separate 5S rDNA sites in chromosomes 3, 8 and 13. In 16-chromosome species, a separate 5S rDNA site was also located in chromosome 3, whereas in 18-chromosome species it was found in the long arm of NOR-chromosome 1. Thus, the difference in localization of rDNA sites in species with 2n = 16, 2n = 30 and 2n = 18 confirms taxonomists opinion, who attributed these species to different sects. Linum and Adenolinum, respectively. The obtained results suggest that species with 2n = 16, 2n = 18 and 2n = 30 originated from a 16-chromosome ancestor.     

Cytogenetics of the European plethodontid salamanders of the genus Hydromantes (Amphibia,Urodela)

A karyological analysis was carried out on different European species of the genus Hydromantes (Plethodontidae). All the species examined share the same chromosome number (2n=28) and, with the exception represented by pair XIV, morphologically similar karyotypes. While the karyotypes display a similar distribution — mainly centromeric and pericentric — of C-heterochromatin, quantitative variations in pericentric heterochromatin are observed among species. In the continental species Hydromantes italicus and ambrosii as well as in the eastern Sardinian species imperialis, flavus and specie nova, pair XIV consists of heteromorphic sex chromosomes of the XX/XY type. It is proposed that the differentiation of the Y might have taken place through the occurrence of a structural rearrangement, such as a pericentric inversion, starting from a hypothetical, homomorphic pair XIV. A sex-related heteromorphism is not found in the western Sardinian species H. genei. A further karyological differentiation among these species concerns the position of the nucleolus organizing region (NOR), which is located on chromosome XII (H. italicus and ambrosii) or on chromosome X, close to the centromere (H. genei, H. imperialis and H. specie nova), or in an intercalary position (H. flavus). The location and the number of the 5 S DNA sites have been conserved during species divergence. On the basis of these karyological data, as well as of results obtained through a preliminary restriction enzyme analysis of the ribosomal and genomic DNAs, the phyletic relationships among the European Hydromantes species are discussed.     

Karyotypic analysis of <Emphasis Type="Italic">Skimmia japonica</Emphasis> (Rutaceae) and related species

A karyotypic analysis of three species of Skimmia (Rutaceae) in East Asia was performed that examined 88 individuals from 53 localities. Chromosome numbers of S. japonica, S. reevesiana and S. arisanensis were 2n=30, 31, 32 (=30+0−2B), 2n=60 and 2n=60, respectively. The chromosome number of S. arisanensis was reported for the first time. All species had a large chromosome pair or quartet (the first pair or quartet) with a median–submedian centromere in the karyotype. In S. japonica the arm ratio of this first pair was considerably variable and showed a geographical pattern. In the northern half of the distribution range, Sakhalin, Hokkaido, Honshu, Shikoku and part of Kyushu, the arm ratio was 1–1.2, while in the southern half, part of Kyushu, Ryukyu and Taiwan, the arm ratio was very variable and ranged from 1.2 to 2.4. In S. japonica the first pair was sometimes rather heteromorphic; however, the heteromorphism was not related to sex of the plant.     

Divergent calcium signaling in RBCs from <Emphasis Type="Italic">Tropidurus torquatus</Emphasis> (Squamata – Tropiduridae) strengthen classification in lizard evolution

Background  

We have previously reported that a Teiid lizard red blood cells (RBCs) such as Ameiva ameiva and Tupinambis merianae controls intracellular calcium levels by displaying multiple mechanisms. In these cells, calcium stores could be discharged not only by: thapsigargin, but also by the Na⁺/H⁺ ionophore monensin, K⁺/H⁺ ionophore nigericin and the H⁺ pump inhibitor bafilomycin as well as ionomycin. Moreover, these lizards possess a P2Y-type purinoceptors that mobilize Ca²⁺ from intracellular stores upon ATP addition.     

The impact of plant associations on Macrosteles quadrilineatus management in carrots

Habitat diversification can influence the interactions of insects with plants and this can be used in agroecosystems for the management of pest populations. Plant diversification can be achieved through planting crops, such as trap crops, or by adjusting weed management. Aster leafhopper, Macrosteles quadrilineatus Forbes (Hemiptera: Cicadellidae), is a polyphagous species that uses cereals, vegetables, and weeds as host plants. The influence of weeds on M. quadrilineatus abundance was investigated experimentally in carrot [Daucus carota L. cv. Canada (Apiaceae)] field plots by adjusting the level of management of two groups of weeds (broadleaf and grass) and by comparing it to weed‐free plots. The preference of M. quadrilineatus for different cereal and weed species relative to carrots was tested in choice test assays. Habitat context influenced the abundance of M. quadrilineatus in the field experiments. The presence of border crops such as oat, rye, barley, wheat, and triticale did not significantly attract or repel this insect to carrot plots compared to the no‐border treatment. However, spelt‐bordered plots had 42% fewer M. quadrilineatus than three treatments, triticale, wheat, and barley, that had the highest insect abundance. The type of weed management affected M. quadrilineatus abundance in carrot plots, but not the frequency of herbicide application. Plots that had carrot growing with broadleaf‐weeds had about 59% fewer M. quadrilineatus compared with those growing with crabgrass or carrot alone. In the greenhouse choice tests, grasses (e.g., cereals) attracted and broadleaf‐weeds repelled M. quadrilineatus relative to carrots. In summary, carrot growers may be able to manage this pest by reducing the interaction of cereal cover crops with carrots and eliminating grassy weeds in commercial production fields.     

Molecular cytogenetic characterization of alien introgressions with gene Fhb3 for resistance to Fusarium head blight disease of wheat

Fusarium head blight (FHB) resistance was identified in the alien species Leymus racemosus, and wheat-Leymus introgression lines with FHB resistance were reported previously. Detailed molecular cytogenetic analysis of alien introgressions T01, T09, and T14 and the mapping of Fhb3, a new gene for FHB resistance, are reported here. The introgression line T09 had an unknown wheat-Leymus translocation chromosome. A total of 36 RFLP markers selected from the seven homoeologous groups of wheat were used to characterize T09 and determine the homoeologous relationship of the introgressed Leymus chromosome with wheat. Only short arm markers for group 7 detected Leymus-specific fragments in T09, whereas 7AS-specific RFLP fragments were missing. C-banding and genomic in situ hybridization results indicated that T09 has a compensating Robertsonian translocation T7AL·7Lr#1S involving the long arm of wheat chromosome 7A and the short arm of Leymus chromosome 7Lr#1 substituting for chromosome arm 7AS of wheat. Introgression lines T01 (2n = 44) and T14 (2n = 44) each had two pairs of independent translocation chromosomes. T01 had T4BS·4BL-7Lr#1S + T4BL-7Lr#1S·5Lr#1S. T14 had T6BS·6BL-7Lr#1S + T6BL·5Lr#1S. These translocations were recovered in the progeny of the irradiated line Lr#1 (T5Lr#1S·7Lr#1S). The three translocation lines, T01, T09, and T14, and the disomic addition 7Lr#1 were consistently resistant to FHB in greenhouse point-inoculation experiments, whereas the disomic addition 5Lr#1 was susceptible. The data indicated that at least one novel FHB resistance gene from Leymus, designated Fhb3, resides in the distal region of the short arm of chromosome 7Lr#1, because the resistant translocation lines share a common distal segment of 7Lr#1S. Three PCR-based markers, BE586744-STS, BE404728-STS, and BE586111-STS, specific for 7Lr#1S were developed to expedite marker-assisted selection in breeding programs.     

The somatic chromosome complements of 16 species of falconiformes (Aves) and the karyological relationships of the order

Using short term leucocyte culture techniques, the somatic chromosome complements of 16 species of diurnal birds of prey, belonging to four different families of the order Falconiformes were studied. The karyotypes are described and illustrated, and of some species idiograms are presented. In accordance with the family classification, four karyologically different groups can be distinguished in the Falconiformes: (1) Cathartidae, with karyotypes which show only 7 pairs of biarmed macrochromosomes and a considerable number of small acrocentrics and microchromosomes (the diploid numbers are approximately 80). This is the only group in which really large macrochromosomes are found (over 10% TCL); (2) Falconidae, the karyotypes of which include only a single pair of biarmed macrochromosomes, all other elements being acrocentrics of medium to small size or microchromosomes (diploid numbers of approximately 84 and 52); (3) the secretary bird (Sagittariidae), with 36 biarmed macrochromosomes and 44 small acrocentrics and microchromosomes (2n=80 approximately); (4) Accipitridae, the representatives of which never possess more than about 8 real microchromosomes, while their karyotypes show varying numbers of biarmed and acrocentric macrochromosomes of small to medium size (diploid numbers range from 78 to 60).The possible karyological relationships within each of these groups are briefly discussed, while a more extensive discussion is dedicated to the possible relationships between these groups, and those between them and other avian taxa.The variation in karyotypic structures found in the Falconiformes is much wider than that in other avian groups. However, it remains an unanswered question whether this karyological heterogenelty points to a polyphyletic origin of the diurnal birds of prey. Especially the chromosome complements of the Accipitridae are most uncommon among birds, because of their extremely low numbers of real microchromosomes. However, of all the Falconiformes only the karyotypes of the Cathartidae have clear counterparts outside the order, since nearly identical complements were found in representatives of the Phoenicopteriformes and Gruiformes.The present work was partially carried out at the Institute of Genetics and the Center for Clinical Cytogenetics (both in Utrecht).     

Differentiation of large-scaled redfin <Emphasis Type="Italic">Tribolodon hakonensis</Emphasis> (Pisces,Cyprinidae) in the Russian part of the range as inferred from the data of karyological analysis and PCR-RFLP analysis of mitochondrial DNA

Considerable differences in karyotypes of Tribolodon hakonensis from Primorye and the rivers of the Sea of Okhotsk drainage were demonstrated. These differences raise doubts that these fishes belong to one species and point to the necessity of more precise definition of the species status of the southern form of T. hakonensis. The karyological evidence is consistent with the data of mtDNA PCR-RFLP analysis on genetic independence of the southern and the northern forms of T. hakonensis. In the northern form of T. hakonensis, variation of the chromosomal arm number was revealed. Specifically, the number of chromosomes was constant (2n = 50), whereas the number of chromosomal arms (NF) constituted 88, 92, and 94, which suggests genetic heterogeneity of the northern form. PCR-RFLP analysis of mtDNA showed that haplotypes of northern T. hakonensis split into two groups with 100% support. Based on comparative phylogenetic and karyological analyses of the Tribolodon species, independent divergence of the southern and the northern forms of T. hakonensis was suggested.     

Chromosomal evolution of South American Columbiformes (Aves)

Karyotypes are compared of 14 species of Brazilian Columbiformes (family Columbidae): Claravis pretiosa (2n=74), Columba cayennensis (2n=76), Columba picazuro (2n=76), Columba speciosa (2n=76), Columbina minuta (2n=76), Columbina passerina (2n=76), Columbina picui (2n=76), Columbina talpacoti (2n=76), Geotrygon montana (2n=86), Leptotila rufaxilla (2n=76), Leptotila verreauxi (2n=78), Scardafella squammata (2n=78), Uropelia campestris (2n=68) and Zenaida auriculata (2n=76). The macrochromosomes of each species were analysed by conventional Giemsa staining, cytobiometrically and with G-and C-banding.All species studied are characterized by typical bird karyotypes with a few pairs of macrochromosomes and many microchromosomes.The morphology and relative length of the Z chromosome are nearly the same in all species, but the W chromosome shows variation. The G-band patterns of the first pair in Columbiformes show a large positive band distally in the long arm, common to all species of the order. The constitutive heterochromatin is restricted to the centromeres of the macro- and microchromosomes. The W is the most heterochromatic chromosome in all species studied.Studies of relative lengths, arm ratios and G- and C-banding patterns showed that in Columbiformes pairs 3, 4 and 5 are the most stable. The types of rearrangements distinguishing between species vary among the genera: pericentric inversions in Columba; fusions and translocations in Uropelia; centric fissions in Geotrygon; fusions, translocations, para and pericentric inversions in Columbina, Leptotila, Zenaida and Scardafella.On the basis of the karyological findings the phylogenetic relationships of the Brazilian Columbiformes are discussed.This work was supported by Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (Plano Integrado de Genética-Processo No. 22.1375/77 and 40.0499/80).     

A cytogenetic study of R. constantinopolitanus and R. sericeus (Ranunculaceae) in Iran

With 600 species Ranunculus is the largest genus in Ranunculaceae, and has a broad global distribution. We studied the karyotypes of R. constantinopolitanus and R. sericeus species of Ranunculaceae and identified their symmetry level. New chromosome numbers of 2n = 21 (Nodeh woods population) and 2n ca. 63 (Javaherdeh population) are reported for R. constantinopolitanus. Two different populations of R. sericeus had two different chromosome results. We investigated morphological and karyological studies along with pollens micromorphology. Different populations of R. constantinopolitanus and R. sericeus, with different chromosome numbers showed morphological and micromorphological differences. Therefore, we considered the two populations of R. sericeus as cytotypes. There was a correlation between the studied morphological characters and pollen size with ploidy levels in the two R. constantinopolitanus populations.     

Tetraploid-octoploid relationships and karyological evolution in the order Acipenseriformes (Pisces) karyotypes,nucleoli, and nucleolus-organizer regions in four acipenserid species

The karyotypes of four Acipenseriformes species, Acipenser gueldenstaedti, 2n=250±8, A. ruthenus, A. stellatus and Huso huso, 2n=118±2, are described. In all four karyotypes the majority of chromosomes are meta- and submetacentric macrochromosomes, and microchromosomes of different morphology make up about one third of the set. In A. ruthenus the NORs are located in the telomeric region of a pair of microchromosomes and at least in one pair of middle-size acrocentrics, and in A. stellatus and Huso huso also in the telomeric regions of at least one pair of microchromosomes. The modal number of active nucleoli in A. gueldenstaedti nuclei amounts to 6–8 (range 2–12), in A. ruthenus, A. stellatus and H. huso nuclei to 2–3 (range 1–6). The data obtained point to the tetraploid origin of Acipenseriformes species with 120 chromosomes and to the octoploid origin of species with 240–260 chromosomes.     

Chromosome polymorphism in <Emphasis Type="Italic">Rineloricaria pentamaculata</Emphasis> (Loricariidae,Siluriformes) of the Paraná River basin

Cytogenetic analysis in three Rineloricaria pentamaculata populations revealed diploid number 2n = 56 chromosomes, karyotype formula 8m/sm + 48st/a and FN = 64. Owing to the presence of the heteromorphic chromosome pair with a big submetacentric chromosome and a small acrocentric one in both males and females, 42.9% of specimens in the Tauá Stream population had the karyotype formula 9m/sm + 47st/a and FN = 65. Analysis of the nucleolus-organizing region by Ag-NOR and FISH techniques showed a single NOR system at pair 5 for R. pentamaculata populations of the Keller River and the Tauá Stream. However, specimens of populations of the Tatupeba Stream had multiple NOR systems at pairs 5 and 8. A constitutive heterochromatin pattern in R. pentamaculata is mainly distributed in the pericentromeric and telomeric regions with interstitial markers in certain chromosomes. Heterochromatin is located in the telomeric and centromeric positions of the acrocentric chromosome in the heteromorphic pair of the Tauá Stream population. In the submetacentric chromosome the markings are located in the telomeric (short arm), pericentomeric and interstitial (long arm) positions. The origins of polymorphisms are discussed.     

Chromosomes of Syrphidae

In this report the karyotypes of 54 species of the tribe Milesiini and of four species of the tribe Myoleptini are described in detail with illustrations and idiograms. These species belong in the genera Lejota, Myolepta, Blera, Calliprobola, Criorhina, Hadromyia, Milesia, Somula, Sphecomyia, Spilomyia, Syritta, Temnostoma, Tropidia and Xylota. Six species have 2n = 8 chromosomes, 35 have 2n = 10 (including Xylota nemorum which has about 20 extra microchromosomes in some specimens), 15 have 2n = 12, one has 2n = 14, and Somula decora has 2n = 10 large chromosomes plus about eight microchromosomes. The mean total complement length (TCL) for 347 complements analysed in these tribes was 53.7 but there is great variation between TCL's of complements analysed even from a single fly. Karyotypes of species of Myolepta in the Myoleptini resemble in certain respects those of species of Tropidia in the Milesiini. Our observations support Currran's transfer of Lejota cyanea to the Milesiini. The 2n = 12 karyotypes of species of Blera, Criorhina, Lejota, Milesia, and to a lesser extent Sphecomyia, have some features in common. Spilomyia species have rather distinct 2n = 10 karyotypes. Certain species in Calliprobola, Syritta and Hadromyia are karyologically similar to some species of the genus Xylota in which species studied fall into fairly distinct karyological groups. These observations provide clear evidence of the accumulation of karyotypic variations in the origin of species in these two tribes.     

Variable B chromosomes frequencies between males and females of two species of pufferfishes (Tetraodontiformes)

Cytogenetic analysis in two sympatric species of pufferfish from Paraná Coast, Brazil, Sphoeroides spengleri (Tetraodontidae) and Chilomycterus spinosus (Diodontidae) revealed the presence of 2n = 46 and 2n = 50 chromosomes, respectively. In S. spengleri, the double FISH technique with 5S and 18S rDNA probes showed no syntenical organization, with both multigene families occupying a terminal position on the chromosomes. In S. spengleri the poor pattern of heterochromatin distribution is discussed about its relation with the compactness of their genome. On the other hand C. spinosus presented conspicuous blocks occupying the short arms of several chromosomes, possibly consequence of an accumulative process. Heterochromatic supernumerary chromosomes were detected in both species, however in S. spengleri they were presented as microchromosomes varying of 0–3 and being more frequent in females than in males, possibly as result of a preferential segregation. Conversely in C. spinosus an extra chromosome was restricted to the males, which to behave as univalent during meiosis. In view of these peculiarities we hypothesized a possible relationship between B chromosome and sex determination, although others aspects on accumulation, maintenance, and frequency of these extra elements were also considered, focusing on the parasitic model. In spite of the karyotypic diversity and others genetic peculiarities in Tetraodontiformes, this corresponds the third report of the occurrence of chromosomes B in the group.     

Cytotaxonomy of some species of the South American genus Lessingianthus (Asteraceae, Vernonieae)

Mitotic chromosome numbers of 32 populations belonging to 23 species of the genus Lessingianthus H.Rob. (Vernonieae, Asteraceae) were determined. The chromosome number of all examined plants was found to be based on x = 16. The numbers observed varied from 2n = 32 to 2n = 176. The results include the first report of the chromosome number for 11 species: L. lanatus (2n = 32), L. varroniifolius (2n = 32), L. cataractarum (2n = 64), L. intermedius (2n = 64), L. argenteus (2n = 96), L. centauropsideus (2n = 96), L. profusus (2n = 96), Lessingianthus sp. nov. 1 (2n = 96), Lessingianthus sp. nov. 2 (2n = 128), L. robustus (2n = 160), and L. macrocephalus (2n = 176). New chromosome numbers were found in the four other species: L. rubricaulis, L. laniferus, and L. sellowii were tetraploid with 2n = 64, while L. oxyodontus was hexaploid with 2n = 96. B chromosomes were observed in L. coriaceus and L. varroniifolius. Lessingianthus macrocephalus (2n = 11x = 176) is reported as the first case of an odd polyploid and the higher chromosome number of Lessingianthus. The significance of the results is discussed in relation to chromosomal data available for the genus.     

Assessment of intergenomic recombination through GISH analysis of F1, BC1 and BC2 progenies of Tulipa gesneriana and T. fosteriana

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.