Interspecific crossability studies in poplars

Summary Pollen-stigma interactions were studied with scanning electron microscopy in intraspecific and intersectional crosses of Populus tremuloides (Sect. LEUCE); P. deltoides, P. nigra (Sect. AIGEIROS); and P. trichocarpa (Sect. TACAMAHACA). Intraspecific variation in hydration, size of hydrated pollen grains, and tube morphology is described. Exine sculpture in P. tremuloides was densely spinulate or scabrate, in P. trichocarpa densely reticulate, in the other species somewhat intermediate. In six of seven intersectional cross combinations pollen-tube behavior on the stigmatic surface at 5–22 hours after pollination was the same as in conspecific matings; in P. tremuloides x P. trichocarpa crosses, the percentage of twisted and bulging tubes was significantly higher. Irradiated mentor pollen did not affect pollentube behavior of adjacent incompatible pollen, but increased hybrid seedling production in interspecific crosses. By contrast, hexane treatment of pollen or stigma, and the spraying of catkins with gibberellic acid or naphtalene acetic acid were ineffective. The results are discussed in relation to several mechanisms presumed to be involved in restricting gene exchange among poplar species; and in relation to Hogenboom's (1973) incongruity concept.     

Distribution of Miogypsinoides in the Zagros Basin,in southwest Iran

In the present study three species of Miogypsinoides are described from the Oligocene–Miocene Asmari Formation of the Zagros Basin in the southwest of Iran. This is the explanation of the morphological recognition and distribution of Miogypsinoides complanatus, Miogypsinoides formosensis (Upper Oligocene, Chattian) and Miogypsinoides dehaartii (Lower Miocene, Aquitanian). Nepionic acceleration is the most important factor for recognition of Miogypsinoides species. Also it is applied in stratigraphic correlation. Examination of samples indicates a decreasing number of nepionic chambers (Mx) as time passes so M. dehaartii with Mx < 10 belong to the Aquitanian age. The study of microfacies shows that these species lived in an open marine environment with normal salinity and medium hydraulic energy in a middle ramp position.     

Tapesia yallundae collected from wheat stubble in South Africa

Tapesia yallundae var.yallundae is newly recorded from wheat stubble collected near Moorresburg in the western Cape Province of South Africa. Apothecia were observed on wheat stubble incubated for 8 months at 10°C under near-ultraviolet light. Single ascospore isolates produced colonies typical of the Wheat (W)-type in culture. Apothecia were also induced after single-conidial isolates were mated on wheat stubble and incubated at 10–15°C for 6 months. All single-conidial isolates were of the W-pathotype (Ramulispora herpotrichoides var.herpotrichoides).     

Intrachromosomal mapping of crossability genes in wheat (Triticum aestivum)

Summary Intrachromosomal mapping studies were used to locate the positions of the genes Kr1 and Kr2, which control the crossability of wheat with Hordeum bulbosum, on chromosomes 5B and 5A, respectively. The location of Kr1 was established using the telocentric mapping technique and found to be on the long arm of chromosome 5B, distal to the centromere with a mean recombination frequency of 44.8±3.28%. Kr2 was located on the long arm of chromosome 5A by linkage with the major gene markers Vrn1, controlling vernalization requirement, and q, controlling ear morphology. Kr2 is closely linked to Vrn1, with a mean recombination frequency of 4.8±4.66%, and is distal to q with a mean recombination frequency of 38.1±10.60%. The similar locations of Kr1 and Kr2 on homoeologous chromosomes suggest that these two loci are homoeoallelic. Significant correlations between Hordeum bulbosum and rye crossability confirmed that Kr1 and Kr2 control the crossability of wheat with both species.     

Cytogenetic studies in motile sperm from normal men

Summary Most studies on human sperm chromosomes from normal men involve the heterologous fertilization of zona free hamster eggs by unselected human sperm. In this work, we have performed cytogenetic studies of highly motile sperm, selected by a swim-up method. A total of 505 motile human sperm complements from three normal donors was analysed. The total frequency of sperm with chromosomal abnormalities (10.9%; 6.9% structural aberrations and 4.0% aneuploidy) and the sex ratio (50.4% X49.6% Y) were similar to those obtained from whole semen samples. Our results indicate that the selection of motile sperm does not imply chromosomal selection.     

Detection of QTLs for crossability in wheat using a doubled-haploid population

 An intervarietal molecular-marker map was used for the detection of genomic regions influencing crossability between wheat (Triticum aestivum L. em Thell) and rye (Secale cereale L.). Analysis of deviance and logistic marker-regression methods were conducted on data from doubled haploid lines from a cross between “Courtot” and “Chinese Spring”. A major quantitative trait locus (QTL) involved in crossability, associated with the marker Xfba367-5B, was detected on the short arm of chromosome 5B. An additional locus, Xwg583-5B, was indicated on the long arm of chromosome 5B. This minor QTL might correspond to Kr1 which was presumed to be the major gene controlling crossability. Another locus of the genome, Xtam51-7A on chromosome 7A, was significantly associated with this trait. Alleles of “non-crossability” were contributed by the non-crossable cultivar “Courtot”. The three-marker model explains 65% of the difference in crossability between the two parents. The present results are discussed in relation to those previously carried out to locate the Kr genes by using the telocentric mapping technique. Received: 27 February 1998 / Accepted: 15 May 1998     

Cytogenetic investigations in rye,wheat and triticale

Summary Chromosomes of tetra- and hexaploid wheat have been individually characterized by Giemsa and/or Leishman C-banding techniques. Appropriate methodological modifications resulted in almost identical staining of chromosomes of tetraploid wheat with Giemsa and Leishman solutions. Additionally comparison of Giemsa banded chromosomes of the A- and B-genome of Triticum turgidum 34 and Triticum aestivum cv Jubilar reveals similar or corresponding patterns in all homologous chromosomes with the exception of chromosome 7B. Apart from this intervarietal variation in certain homologous chromosomes of both wheat cultivars, intravarietal polymorphism is verified.     

Cytogenetic evaluation of in vitro matured bovine oocytes collected from ovaries of individual donors

Oocytes were collected after slaughter by aspiration from pairs of ovaries of individual donors. A total of 656 oocytes was selected for IVM from 74 pairs of ovaries (8.9 oocytes per pair, ranging between 1 and 25). The oocytes were matured in droplets of maturation medium (TCM-199 medium supplemented with 20% estrous cow serum (ECS), 50 microg/ml gentamycin, 10 microg/ml FSH, 1 microg/ml estradiol-17beta). Cytogenetic analysis of 348 oocytes showed 79 at the first metaphase (MI; 22.7%, 79 348 ), 11 at the first telophase (TI; 3.2%, 11/348 ), and 258 at the second metaphase (MII; 74.1% 258/348 ). Significant differences (P < 0.01) were shown among the donors regarding the number of oocytes selected for IVM and the number of oocytes matured for IVF.     

A Bayesian modeling of wildfire probability in the Zagros Mountains,Iran

The preparation of probability distribution maps is the first important step in risk assessment and wildfire management. Here we employed Weights-of-Evidence (WOE) Bayesian modeling to investigate the spatial relationship between historical fire events in the Chaharmahal-Bakhtiari Province of Iran, using a wide range of binary predictor variables (i.e., presence or absence of a variable characteristic or condition) that represent topography, climate, and human activities. Model results were used to produce distribution maps of wildfire probability. Our modeling approach is based on the assumption that the probabilities reflect the observed proportions of the total landscape area occupied by the corresponding events (i.e., fire incident or no fire) and conditions (i.e., classes) of predictor variables. To assess the effect of each predictor variable on model outputs, we excluded each variable in turn during calculations. The results were validated and compared by the receiver operating characteristic (ROC) using both success rate and prediction rate curves. Seventy percent of fire events were used for the former, while the remainder was used for the latter. The validation results showed that the area under the curves (AUC) for success and prediction rates of the model that included all thirteen predictor variables that represent topography, climate, and human influences were 84.6 and 80.4%, respectively. The highest AUC for success and prediction rates (86.8 and 84.6%) were achieved when the altitude variable was excluded from the analysis. We found slightly decreased AUC values when the slope-aspect and proximity to settlements variables were excluded. These findings clearly demonstrate that the probability of a fire is strongly dependent upon the topographic characteristics of landscapes and, perhaps more importantly, human infrastructure and associated human activities. The results from this study may be useful for land use planning, decision-making for wildfire management, and the allocation of fire resources prior to the start of the main fire season.     

A new and eyeless cobitid fish (Pisces, Cypriniformes) from the Zagros Mountains, Iran

The first blind, and colourless, noemacheiline cobitid fish is described and compared with other cave-dwelling species of the subfamily. The new taxon, recently discovered in a natural well connected with subterranean waters in the Zagros Mountains of Iran, coexists with the blind depigmented cyprinid fish Iranocypris typhlops discovered in 1937. Some consideration is given to the generic status of the new species and its relationships to other noemacheilines.     

Cytogenetic studies on wild house mice from Belgium

The present status of Robertsonian karyotype variation in populations of wild mice from Belgium is presented. Two fusions, Rb(4.12)1Nam and Rb(5.10)3Nam, were identified in the central plain of this flat country. Surrounding this region only mice with the usual 2n=40 karyotype occurred. From the distribution pattern some possible relationships to other Rb populations from Europe are discussed.     

Cytogenetic studies in spontaneous abortuses

Summary In a series of 450 products of conception received for cytogenetic analysis, tissue culture was attempted on 309, and karyotypes were established using banding techniques in 154 singleton specimens. Abnormalities of karyotype were identified in 19%; of these abnormalities, 48% were autosomal trisomies. Gestational age was decreased in the abnormal specimens, and their developmental age was retarded by comparison with their gestational age. Factors contributing to the relatively low incidence of abnormality are examined. The major factor appears to be the clinical interest of collaborating staff, leading to selection, either intentional or unintentional, of particular phenotypes and hence a non-random series. A negative relationship is suggested between frequency of monsomy X and autosomal trisomy, both being associated with maternal age.     

Photosynthetic pigments,ionic and antioxidative behaviour of hulled tetraploid wheat in response to NaCl

Salt stress causes extensive losses to agricultural crops, including wheat, throughout the world and has been the focus of wide research. Though, information is scarce on the potential of ancient wheat relatives in tackling this major limiting factor. Thus, six hulled tetraploid wheat genotypes (HW) were compared to a free-threshing durum wheat genotype (FTW) under different NaCl concentrations, ranging from 0 to 150 mM, at early growth stages in a sand culture experiment. Salt stress induced significant declines in the leaf chlorophyll (Chl) a, Chl b, total Chl, and carotentoid contents; the extent of the declines was greater in FTW compared to HW. Mean leaf proline (3.6-fold) and Na⁺ (1.58-fold) concentrations and Na⁺/K⁺ (2.48-fold) drastically increased with 150 mM of NaCl; the magnitude of the increases was greater in HW compared to FTW. While the carotenoids concentration decreased with progressive salinity both in HW and FTW, the activities of antioxidant enzymes, i.e., catalase, ascorbate peroxidase, and peroxidase were reduced in FTW, but remained unchanged in HW. The above responses to 150 mM NaCl were associated with a significant decrease in shoot dry mass of FTW and lack of significant changes in that of HW. Findings of the present study could help pave the way for further studies on physiological and molecular mechanisms of salt tolerance in these durum wheat relatives.