Robertsonian change in allies ofZebrina (Commelinaceae)

Meiotic pairing inTradescantia soconuscana 2n=26 (6M+16A+4T) suggests that it has a tetraploid constitution which is not apparent in its chromosome number. Its nombre fondamental of 32 indicates that it could have evolved from an ancestor with x=8 by a combination of Robertsonian fusion, hybridization and polyploidy. The 2n=16 (8A+8T) karyotype of a closely related diploid supports this. The allied genusZebrina may have followed a similar method of chromosome evolution.     

Natural hybridization between an outcrossing and a selfingPhlox (Polemoniaceae): The maternal species of F1 hybrids

Natural F₁ hybrids between the outcrossingPhlox drummondii and the predominantly selfingP. cuspidata were examined to ascertain the proportion of hybrid individuals mothered by each species. Species-specific restriction fragment patterns (both nrDNA and cpDNA) were established as markers, and synthetic hybrids of known parentage were utilized to determine that the chloroplast genome is maternally inherited. Of 89 mature natural hybrids examined, approximately two thirds were mothered byP. drummondii, the outcrosser. That the outcrosser should mother most hybrids is expected since it is dependent upon incoming pollen for fertilization, and hybrids may result when heterospecific pollen is received. The fact that the highly selfingP. cuspidata mothered nearly one third of the hybrids is surprising, and may be related to both pre-zygotic and post-zygotic factors. Which species mothers hybrids has important implications for the potential for introgression as well as its direction.     

Chromosome pairing in tetraploid hybrids between Lolium perenne and L. multiflorum

Summary Chromosome association at first meiotic metaphase in tetraploid hybrids between Lolium perenne and L. multiflorum was compared with that in autotetraploid L. perenne. The hybrids were found to have significantly higher levels of bivalent frequency, and lower levels of multivalent and chiasma frequency. A significant increase in multivalent frequency with increasing chiasma formation was found in both groups, but the increase was much less in the hybrids. These differences in chromosome associations between the two groups must therefore reflect differences in chiasma distribution and it is suggested that the results indicate a significant degree of preferential bivalent pairing in the hybrids.     

Resistance of tomato F1 hybrids to grey mold

A two-year estimation of Botrytis cinerea stem damage of 299 experimental F₁hybrids grown in 2 rotations: winter-autumn and summer-autumn was carried out. The estimation was made in a period of mass fruitage. As a result it was shown, that the hybrids with determinate type of growth (sp) are damaged more strongly than indeterminate ones (sp +). An average disease severity in the first group was 2.8 against 2.3 in the second one using a scale 0–4. Number of strongly injured (2.5–4) plants in each group were 44.1 % and 30.7 % and number of moderate resistant (0–1.5 numbers) plants were 10 % and 8.5 % accordingly. The analysis of resistance of F₁ hybrids determined significant influence of parental lines on a degree of a damage of plant stems by B. cinerea.     

Analysis of production,early growth and survival ofClarias gariepinus (Burchell),Heterobranchus longifilis (Val.) (Pisces: Clariidae) and their F1 hybrids in ponds

Clarias gariepinus andHeterobranchus longifilis were successfully hybridized to produce reciprocal F₁ progeny during a two-year study.C. gariepinus produced significantly heavier spawn thanH. longifilis during the same period. Fertilized eggs were incubated in aerated static-water in fibre-glass troughs, and hatching rates were not found to be significantly different (P<0.05) between any two of the four catfish groups produced. Eight-day old fry of each group were reared in fertilized nursery ponds, and F₁ hybrids fromH. longifilis maternal parent had the best growth and survival rates at the end of 18 days. The reciprocal cross showed intermediate growth rate between both parents. At harvest, differential growth was less pronounced among both hybrids than among the parents.     

Genetic segregation in relation to chromosome pairing in tetraploid hybrids between Lolium perenne and L. multiflorum

Summary Segregation at one of the loci controlling tiller-base pigmentation was studied to determine the mode of inheritance in tetraploid hybrids between Lolium perenne and L. multiflorum. The results could be explained by tetrasomic inheritance and thus did not support previous reports of a degree of preferential chromosome pairing in this material. However, double reduction and aneuploidy may to some extent have masked any tendency to disomic segregation brought about by preferential pairing. Moreover, there was significant heterogeneity between families in the segregation ratios which may indicate genetically controlled differences in pairing behaviour. The results are related to previous cytological and genetic studies.     

Cytology of F1 hybrids and chromosome number of F2 and BC1 progeny of the cross Bromus riparius x B. inermis

Summary Hybrids between B. inermis Leyss (2n=8x=56) and B. riparius Rehm. (2n=10x=70) were easily made. The F₁ hybrids had a fertility of 20%–50% under open pollination and backcrossing to B. inermis. Chromosome pairing in B. riparius was predominantly as bivalents (29.04–33.85 per cell for plant means). Bivalents also predominated in the F₁ hybrid (2n=9x=63) and there was a high level of pairing with no reduction in chiasma frequency. It was impossible to estimate the frequency of auto-versus allosyndetic pairing. Chromosome pairing in a hybrid between B. arvensis (2n=2x=14) and B. riparius confirmed that the B. riparius complement is capable of complete autosyndetic pairing. Chromosome numbers in the F₂ progeny ranged from 2n=56 to 72 but they were skewed towards 2n=63 to 70. Backcrosses ranged from 2n=56 to 63, as expected, with the distribution skewed towards 2n=56. Selection towards the 2n=56 level would be difficult in the F₂. Empirical observation suggested that cytoplasm had a major influence on morphology in the backcrosses. Additional studies are required to determine the best breeding scheme to introgress germ plasm between B. inermis and B. riparius.     

Cytogenetic study of F1 hybrids betweenCrepis dinarica andCrepis froelichiana (Asteraceae)

Crepis dinarica andC. froelichiana are two closely related species of theC. praemorsa complex. Even though they exhibit the same chromosome number (2n = 8) and similar idiogram shape, they differ widely in quantity and distribution of heterochromatin bands. The hybrids between these two species comprise three morphological types. Parental genomes were distinguished in hybrids by Giemsa differential staining (C-banding). Although meiosis presents only a few abnormalities (about 2.4%), the percentage of aborted pollen grains is very high (90%).     

Multivariate analysis of tooth crown morphology in Japanese-American F1 hybrids

Mesiodistal crown diameters of I1 through M1 and six non-metric crown traits in permanent dentition of Japanese-American F₁ hybrids were compared with those of the parental populations. The hybrids were born of Japanese females and American males, both Caucasians and American Blacks, after World War II and brought up at Elizabeth Saunders Home in Kanagawa Prefecture, Japan. The comparisons were undertaken by means of multivariate analysis methods such as principal component analysis, distance and similarity coefficients and multidimensional scaling. The F₁ hybrids generally occupy an intermediate position of the two parental populations, and this is particularly evident in size component of the crown measurements and in distance analysis of frequencies of the non-metric crown traits. The shape component of the crown measurements, however, not necessarily follows such a rule and suggests a more complicated gene control than in the case of the size component. Also, each measurement and frequency of non-metric trait of tooth crowns in F₁ hybrids is not uniformly at the middle position between their parental populations but this is true when they are analyzed as multivariables.     

Proteomic analysis of F1 hybrids and intermediate variants in a Littorina saxatilis hybrid zone

Proteomic analysis was carried out on the Crab (upper-shore) and Wave (lower-shore) ecotypes of Littorina saxatilis from a hybrid zone at Silleiro Cape, Spain. Proteome profiles of individual snails were obtained. Protein expression in F₁ hybrid snails bred in the laboratory and snails with intermediate shell phenotypes collected from the mid-shore were compared with Crab and Wave ecotypes using analytical approaches used to study dominance. Multivariate analysis over many protein spots showed that the F₁ snails are distinct from both ecotypes but closer to the Wave ecotype. The intermediate snails are highly variable, some closer to the Crab and others to the Wave ecotype. Considered on a protein by protein basis, some proteins are significantly closer in expression to the Crab and others to the Wave ecotype for both F₁ and intermediate snails. Furthermore, a significant majority of proteins were closer in expression to the Wave ecotype for the F₁, consistent with the multivariate analysis. No such significant majority toward either the Crab or Wave ecotype was observed for the intermediate snails. The closer similarity of F₁ and Wave ecotype expression patterns could be the result of similar selective pressures in the similar mid-shore and low-shore environments. For a significantly larger number of proteins, intermediate snails were closer in expression to the ecotype having the lower expression, for both Crab and Wave ecotypes. This is somewhat unexpected as lower expression might be expected to be an indication of impairment of function and lower fitness. Proteomic analysis could be important for the identification of candidate proteins useful for gaining improved understanding of adaptation and barriers to gene flow in hybrid zones.     

Evolutionary relationship between Enterobacteriaceae: comparison of the ATP synthases (F1F0) of Escherichia coli and Klebsiella pneumoniae

The ATP synthase complex of Klebsiella pneumoniae (KF₁F₀) has been purified and characterized. SDS-gel electrophoresis of the purified F₁F₀ complexes revealed an identical subunit pattern for E. coli (EF₁F₀) and K. pneumoniae. Antibodies raised against EF₁ complex and purified EF₀ subunits recognized the corresponding polypeptides of EF₁F₀ and KF₁F₀ in immunoblot analysis. Protease digestion of the individual subunits generated an identical cleavage pattern for subunits , , , , a, and c of both enzymes. Only for subunit different cleavage products were obtained. The isolated subunit c of both organisms showed only a slight deviation in the amino acid composition. These data suggest that extensive homologies exist in primary and secondary structure of both ATP synthase complexes reflecting a close phylogenetic relationship between the two enterobacteric tribes.Abbreviations ACMA 9-amino-6-chloro-2-methoxyacridine - DCCD N,N-dicyclohexylcarbodiimide - FITC fluorescein isothiocyanate - SDS sodium dodecyl sulfate - TTFB 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole     

Production,morphology, and cytogenetic analysis of Elymus caninus (Agropyron caninum) x Triticum aestivum F1 hybrids and backcross-1 derivatives

Summary Intergeneric hybrids were produced between common wheat, Triticum aestivum (2n=6x=42, AABBDD) and wheatgrass, Etymus caninus (Agropyron caninum) (2n=4x=28, SSHH) — the first successful report of this cross. Reciprocal crosses and genotypes differed for percent seed set, seed development and F₁ hybrid plant production. With E. caninus as the pollen parent, there was no hybrid seed set. In the reciprocal cross, seed set was 23.1–25.4% depending upon wheat genotype used. Hybrid plants were produced only by rescuing embryos 12–13 days post pollination with cv Chinese Spring as the wheat parent. Kinetin in the medium facilitated embryo germination but inhibited root development and seedling growth. The hybrids were vigorous, self sterile, and intermediate between parents. These had expected chromosome number (2n=5x=35, ABDSH), very little chromosome pairing (0.51 II, 0.04 III) and some secondary associations. The hybrids were successfully backcrossed with wheat. Chromosome number in the BC₁ derivatives varied 54–58 with 56 as the modal class. The BC₁ derivatives showed unusually high number of rod bivalents or reduced pairing of wheat homologues. These were sterile and BC₂ seed was produced using wheat pollen.     

Chromosome number,morphology, pairing,and DNA values of species and hybrids in the genusFallopia (Polygonaceae)

The taxa in this study have in the past been treated together in sect.Tiniaria Meissner ofPolygonum L. s.l., and more recently the large erect rhizomatous herbaceous perennials have been separated from the twining annuals and perennials as the generaReynoutria andFallopia respectively. These taxa range in ploidy level from diploid to octoploid, with base numbers of both 10 and 11 present. The plants are primarily Asiatic in distribution, although many of the large erect perennials are now naturalized in many parts of Europe. Cytological examination has revealed the presence of a number of previously unknown hybrid taxa in the British Isles. The readiness with which hybridisation occurs between taxa of differing base number and ploidy level, and similarities revealed in chromosome morphology, meiotic pairing and in DNA C-value, suggest to the authors that these two genera are best amalgamated underFallopia.     

An analysis of interspecific hybrids and phylogenetic implications inCucumis (Cucurbitaceae)

Investigations on interspecific crossability in 8Cucumis species (2n = 24) and chromosome pairing and pollen fertility of their hybrids from 15 combinations have been utilized for tracing the phylogenetic relationships among these taxa and factors responsible for their differentiation. A collective evaluation of data suggests that there are three broad groups of species, one of the spiny fruited interfertile species, whose hybrids show varying degree of chromosome associations and low to high pollen fertility; the second of species with non-spiny fruits, which are completely incompatible with the former but weakly compatible with the cultivated species,C. melo L. to produce partly developed seeds, and the third group ofC. metuliferus E. Mey. exSchrad. andC. melo and its different botanical varieties. The species with spiny fruits can be further divided based on karyomorphological similarities and/or on relative genomic affinity, indicated by chromosome pairing and hybrid pollen fertility.Cytogenetics inCucumis III.     

Morphology and cytology of intergeneric hybrids involvingLeymus multicaulis (Poaceae)

The morphology and meiotic behaviour of pollen mother cells were studied in hybrids involvingLeymus multicaulis (2n = 28) ×Psathyrostachys huashanica (2n = 14),L. multicaulis ×P. juncea (2n = 14), andL. secalinus (2n = 28) ×L. multicaulis. Chromosome pairing was almost identical in theL. multicaulis ×P. huashanica, andL. multicaulis ×P. juncea hybrids, in which it averaged 7.30 univalents + 6.69 bivalents + 0.096 trivalents and 7.48 univalents + 6.75 bivalents, respectively. The meiotic pairing in the two hybrids indicated that oneL. multicaulis genome was closely homologous with theP. huashanica andP. juncea genomes. BothP. huashanica andP. juncea are possibly donors of oneL. multicaulis genome. Chromosome pairing in theL. secalinus ×L. multicaulis hybrid averaged 4.49 univalents + 11.71 bivalents + 0.02 trivalents, indicating that the genomes ofL. multicaulis andL. secalinus are to some degree homologous. However, they are sufficiently differentiated to insure species distinctness.     

Biosystematic studies in European species ofGladiolus (Iridaceae)

Representative specimens of the EuropeanGladiolus species (excl.G. palustris) were used to study variability and relationships. 25 characters were measured for cluster, principal component and Wells hybrid analyses (Figs. 1–3). Three (with PCA) respective five (cluster analysis) main groups are revealed. Bulb characteristics appear to be very useful for indentification. The subspecific status ofG. communis subsp.byzantinus is confirmed. Hybrids of four different parental combinations were detected in our collection. Most species include polyploid series. Partly 3x, 4x, 6x, 8x, 12x and aneuploid cytotypes but no diploids were found. Polyploids as pioneers and hybridization of sympatric species are apparently linked to migrations during the glacial periods.     

Cytogenetic characterization of F1, F2 and backcross hybrids of the Neotropical catfish species Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum (Pimelodidae, Siluriformes)

The cytogenetic characteristics of Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum and their F1, F2 and backcross hybrids were assessed by using chromosome banding techniques. The diploid number of 56 chromosomes was constant in all species and lineages, with a karyotypic formula containing 20 metacentric, 12 submetacentric, 12 subtelocentric and 12 acrocentric chromosomes. Nucleolar organizer regions (NORs) were identified in two subtelocentric chromosomes in the parents and hybrids, with partial nucleolar dominance in F1 and F2 specimens. Heterochromatic blocks were detected in the terminal and centromeric regions of some chromosomes in all individuals. For parental and hybrid lineages, 18S ribosomal clusters corresponding to NORs and 5S ribosomal genes were identified in distinct pairs of chromosomes. The striking conservation in the chromosomal macrostructure of the parental species may account for the fertility of their F1 hybrids. Similarly, the lack of marked alterations in the chromosomal structure of the F1 hybrids could account for the maintenance of these features in post-F1 lineages.     

Modulation of nucleotide specificity of thermophilic F(o)F(1)-ATP Synthase by epsilon-subunit

The C-terminal two α-helices of the ε-subunit of thermophilic Bacillus F(o)F(1)-ATP synthase (TF(o)F(1)) adopt two conformations: an extended long arm ("up-state") and a retracted hairpin ("down-state"). As ATP becomes poor, ε changes the conformation from the down-state to the up-state and suppresses further ATP hydrolysis. Using TF(o)F(1) expressed in Escherichia coli, we compared TF(o)F(1) with up- and down-state ε in the NTP (ATP, GTP, UTP, and CTP) synthesis reactions. TF(o)F(1) with the up-state ε was achieved by inclusion of hexokinase in the assay and TF(o)F(1) with the down-state ε was represented by εΔc-TF(o)F(1), in which ε lacks C-terminal helices and hence cannot adopt the up-state under any conditions. The results indicate that TF(o)F(1) with the down-state ε synthesizes GTP at the same rate of ATP, whereas TF(o)F(1) with the up-state ε synthesizes GTP at a half-rate. Though rates are slow, TF(o)F(1) with the down-state ε even catalyzes UTP and CTP synthesis. Authentic TF(o)F(1) from Bacillus cells also synthesizes ATP and GTP at the same rate in the presence of adenosine 5'-(β,γ-imino)triphosphate (AMP-PNP), an ATP analogue that has been known to stabilize the down-state. NTP hydrolysis and NTP-driven proton pumping activity of εΔc-TF(o)F(1) suggests similar modulation of nucleotide specificity in NTP hydrolysis. Thus, depending on its conformation, ε-subunit modulates substrate specificity of TF(o)F(1).     

Low resolution structure of subunit b (b (22-156)) of Escherichia coli F(1)F(O) ATP synthase in solution and the b-delta assembly

The first low resolution solution structure of the soluble domain of subunit b (b _22–156) of the Escherichia coli F₁F_O ATPsynthase was determined from small-angle X-ray scattering data. The dimeric protein has a boomerang-like shape with a total length of 16.2 ± 0.3 nm. Fluorescence correlation spectroscopy (FCS) shows that the protein binds effectively to the subunit δ, confirming their described neighborhood. Using the recombinant C-terminal domain (δ_91–177) of subunit δ and the C-terminal peptides of subunit b, b _120–140 and b _140–156, FCS titration experiments were performed to assign the segments involved in δ–b assembly. These data identify the very C-terminal tail b _140–156 to interact with δ_91–177. The novel 3D structure of this peptide has been determined by NMR spectroscopy. The molecule adopts a stable helix formation in solution with a flexible tail between amino acid 140 to 145.     

Cytogenetic studies of the F1 hybrids of Capsicum annuum with C. chinense and C. baccatum

Summary Partially sterile interspecific hybrids were obtained between C. annuum var. cerasiformis and C. chinense var. mishme (H₁), and C. annuum var. cerasiformis and C. baccatum var. pendulum (H₂). Morphologically the F₁ hybrids were intermediate between the corresponding parents. Meiosis was irregular in the two F₁ hybrids. Cytological analysis of the two F₁ hybrids revealed that the genome of C. annuum differs from C. chinense by two translocations and some minor structural alterations and from C. baccatum by two translocations, a single inversion and some minor structural alterations. Isolation barriers such as hybrid inviability, weakness and hybrid breakdown in the H₁ hybrid and, inaddition, desynapsis in the H₂, were operative in these taxa. The differences between the present findings and those reported earlier on the two F₁hybrids were attributed to differences in the genetic architecture of the taxa employed in hybridization.