Showing papers in "Hereditas in 2004"

Conservation units and translocations : strategies for conserving evolutionary processes

Abstract: The setting of conservation priorities within species requires explicit goals and identification of the appropriate targets for conservation I suggest that the conservation goal should be to conserve ecological and evolutionary processes; rather than to preserve specific phenotypic variants - the products of those processes From this perspective, we should seek to conserve historically isolated, and thus independently evolving, sets of populations (ie, Evolutionarily Significant Units, ESU) This can require manipulation of the component Management Units (MUs), some of which may be phenotypically distinct Here I explore the application of this approach to the design of translocations for conservation management A process-oriented approach suggests that individuals should not be translocated between ESUs, but under some circumstances it is appropriate to mix individuals from different MUs within an ESU These circumstances include augmentation of remnant populations that are showing signs of inbreeding depression or increased fragmentation and the use of mixed stocks for reintroductions into modified or changing environments or for introductions into novel environments These actions are consistent with the goal of maintaining processes, but the extent to which differences in adaptation or coadaptation constrain the viability of populations subject to translocation needs further exploration Both theory and limited experimental evidence suggests that these constraints can be overcome if sufficient genetic variation is present and evolutionary processes can operate without substantially reducing population viability One remaining question is the extent to which genetic coadaptation, and the resulting outbreeding depression, develops along environmental gradients and how this compares to the build-up of genetic incompatibility between historically isolated populations

A Modified Allium Test as a Tool in the Screening of the Genotoxicity of Complex Mixtures

Abstract: A modified protocol for the Allium test with regard to the usually observed microscopic parameters is presented. In three different experiments, Allium root cells were exposed to methyl methanesulfonate (10 and 15 μg/1), nondiluted waste water from a slaughter-house and from a dye-house (the last one without any genotoxic effect). In the proposed scoring method only anaphase and early telophase cells are observed (100 cells per onion), and bridges, fragments, and vagrants are scored and pooled as chromosome aberrations. This method of scoring is compared with the one where metaphase, early anaphase, and normal anaphase cells are observed (100 per onion), and bridges, vagrants, fragments, c-mitoses, and sticky chromosomes are scored and classified separately in these chromosome aberration categories. Using the X2-test it is shown that the proposed modified method of scoring is more sensitive, having higher levels of significance than the more commonly used method. It is recommended to use the modified Allium test as an easy and sensitive screening method of complex mixtures for genotoxicity.

Partial Albinism in a Semi‐Isolated Population of Great Reed Warblers

Abstract: Albinism in birds is thought to result from the expression of recessive alleles that disrupt melanin pigmentation at feather development. We have studied great reed warblers Acrocephalus arundinaceus in a recently founded and increasing population in Sweden during 15 years for the presence of birds with albinistic feathers. The study population was founded in 1978 and the few cases of albinism was exclusively recorded during the first five pears of our study (1985-1989). This fits to the expected pattern if albinism is governed by recessive alleles; we have previously demonstrated that the population suffered from inbreeding during the first years of our study. The albinistic birds experienced a similar lifetime reproductive success as normally coloured birds. (Less)

The role of the barley testa layer and its flavonoid content in resistance to Fusarium infections

Abstract: Developing testa layers of the barley proanthocyanidin-free mutants ant 13-152, anf17-148, ant 18-159, ant19-109, ant22-1508, ant25-264, ant26-485, ant27-489, ant28-484 and ant29-2110 and their mother varieties, were analysed for accumulation of proanthocyanidins and their flavonoid precursors. In vitro infection of developing barley caryopses of wild type and mutants with Fusarium poae, F. culmorum and F. graminearum revealed all mutants except ant18-159 to be more sensitive to Fusarium attack than wildtype. Mutant ant 18-159 showed extreme resistance. Histological investigations of the infection process revealed that the hyphae were unable to penetrate the testa of this mutant. The testa layer of ant 18-159 accumulates small amounts of dihydroquercetin as a result of nonsense mutations in the structural gene for dihydroflavonol reductase. Authentic dihydroquercetin and an autographic assay proves this flavonoid to be a strong inhibitor of Fusarium growth and macrospore formation. Mutant ant 17-148, which accumulates the flavone chrysoeriol as a consequence of a mutation in the step catalysed by flavanone 3-hydroxylase, demonstrates that this flavone is not an inhibitor of Fusariwn growth in vivo. Comparison of flavonoid standards and monomers and polymers from other plants reveal monomeric flavonoids generally to be potent inhibitors of Fusarium.

The Influence of Male and Female Body Size on Copulation Duration and Fecundity in Drosophila Melanogaster

Abstract: We studied two components of the mating system, copulation duration and early fecundity, in relation to body size in Drosophila melanogaster. Body size variation was created experimentally by varying the degree of crowding (starvation) among larvae from an inbred strain, keeping the genetics and temperature as constant as possible. Hence, in contrast to most previous studies, where genetic and environmental variation have been confounded, we aimed at investigating how much pure phenotypic variation could influence copulation duration and early fecundity. It is shown that copulation duration and fecundity both strongly dependent on female body size, but either not or much less so on male body size. Small females mate faster than medium or large females and small females have the lowest fecundity. Among males, medium-size males are more fecund than smaller or larger males, resulting in stabilising selection for intermediate male size. These results are in contrast with previous findings.

Generation and comparison of EST-derived SSRs and SNPs in barley (Hordeum vulgare L.).

Abstract: The progress of genome sequencing projects of model plants like barley, combined with the recent advances of high throughput assays, has provided a wealth of sequence information. This information is being employed to develop a high density transcript map of barley (Hordeum vulgare L.). To achieve this goal, the available EST database is being used as a resource for the development of novel microsatellite (SSR) and single nucleotide polymorphism (SNP) markers. So far, a total of 692 microsatellites representing different di-, tri- and tetra-nucleotide repeats were identified from a set of 19,000 EST sequences. Non-redundant SSRs have been used for mapping and so far 76 microsatellite loci were mapped. In addition to the 180 SNP primer pairs, which were designed to target specific ESTs, 72 were polymorphic among the seven genotypes examined here. Of these, 60 SNPs have been mapped applying a denaturing HPLC approach. To examine the potential of the EST-derived markers for pedigree studies, EST-derived SSRs (75 loci) and SNPs (72 loci) were used to fingerprint a set of seven genotypes. The results show that although both marker types yielded similar groupings, a larger data set of both SSRs and SNPs is necessary to obtain stable clusters in unrelated germplasm.

Identification of two Low-Phytate Barley (Hordeum Vulgare l.) Grain Mutants by TLC and Genetic Analysis

Abstract: Barley grains mutagenized with sodium azide were screened for high levels of free phosphate in order to identify low-phytate mutants. Approximately 2000 M2 half-grains were analyzed by molybdate staining and high free phosphate contents were scored positive for low phytate mutants. Plants were grown from embryo-containing halves of positive samples. Subsequent TLC analysis of positives was used to display free phosphate and phytate simultaneously, and two characteristic low-phytic acid phenotypes (A and B) could be distinguished. A-type grains, which were found for seven plants, contained very high levels of free phosphate, low levels of phytate and trace amounts of other phosphate-containing compounds not observed in wildtype samples. Migration of these novel P-compounds on TLC plates was similar to that of inositol phosphates other than phytate. In grains from the two B-type plants the increase in free phosphate and the decrease in phytate relative to wildtype levels were moderate and additional P-compounds were absent. Genetic tests showed that at least three recessive alleles caused low-phytic acid phenotype A, whereas a separate, recessive locus was responsible for phenotype B. The importance of these findings with respect to the development of new barley varieties with an improved nutritional and environmental value is discussed.

Trends in the karyotype evolution of Loricariidae fish (Siluriformes).

Abstract: Six species of Loricariidae belonging to the subfamilies Hypostominae (Hypostomus emarginatus, Rhinelepsis aspera, Pogonopoma wertheimeri), Ancistrinae (Panaque cf nigrolineatus, Hemiancistrus sp) and Loricariinae (Sturisoma cf nigrirostrum) were studied cytogenetically The results show that 2n = 54 represents the basal diploid number for this fish family Different trends in the karyotypic evolution can be seen among the subfamilies: Hypostominae and Loricariinae species present diversified karyotypic macrostructures, while the Ancistrinae appear to show more conserved karyotypes Among the Hypostominae, the genus Hypostomus had a wide karyotypic variation (2n = 52 to 80), where centric fissions seem to play an important role in this chromosomal divergence The nucleolar organizing regions were diversified, and occurrence of multiple NORs was frequent Heteromorphic chromosomes belonging to distinct sex chromosome systems can also occur infrequently among the Loricariidae

Expression of the heat-shock protein HSP70 in Drosophila buzzatii lines selected for thermal resistance.

Abstract: The level of HSP70 expression induced by a non-lethal high temperature was examined in lines selected for increased thermal resistance and in corresponding control lines of Drosophila buzzatii, in order to test if selection for high temperature resistance leads to an increased level of HSP70 expression. The lines used were selected for up to 64 generations either as adults or through all larval stages. In adult selection lines, hard selection was implemented every second generation after mild heat hardening. In larval selection lines, larvae were exposed each generation to laboratory "natural" selection. Generally lines selected as adults showed a higher HSP70 expression than did controls, both in third instar larvae and in adults. A strong negative response to selection of HSP70 expression was found in all lines that were selected at cycling temperatures during larval development. The results suggests that a trade off between heat resistance in form of HSP70 expression and fecundity/fertility are responsible for the level of HSP70 expression. The effect of the different methods of selection on HSP70 expression suggests that heat resistance constitutes more than one trait.

Genotoxicity of Oil Field Wastewater in Nigeria

Abstract: were cultivated in various concentrations of the wastewater, and after 48 h one root tip from each bulb was harvested and processed for cytological studies by the aceto-orcein squash technique. After 96 h, mean lengths of root bundles were obtained and the Effect Concentration (EC) values calculated. Treatment with wastewater resulted in significant dose- dependent root growth inhibition.

The barley Genome and its Relationship with the Wheat Genomes. A Survey with an Internationally Agreed Recommendation for Barley Chromosome Nomenclature

Abstract: The paper reviews recent literature on the cytology, cytogenetics, molecular cytogenetics, and gene structure of barley, and on the relationship of the barley and wheat genomes. The information collected demonstrates largely similar genetic contents and collinearity of gene loci in the seven chromosomes of barley and in those of other members of the Triticeae. The high level of synteny indicates that the whole group can be considered as a single gene pool. On this basis, the 7th International Barley Genetics Symposium recommended that (i) the currently used designations of the barley chromosomes (the BURNHAM and HAGBERG system) should become secondary to the use of the Triticeae system; i.e., each of the seven barley chromosomes is designated by a numeral between 1 and 7 according to its homoeologous relationship with the chromosomes of the wheat genomes followed by the genomic symbol H, e.g., 2H; (ii) the genomes of Hordeum vulgare and H. bulbosum are symbolized with the letter H; and (iii) the arms of the barley chromosomes are designated by the capital letters S and L (cf. SINGHand TSUCHIYA 1982b). Further, it was recommended that the barley genome present in the barley cultivar ‘Betzes’ should become the reference genome in the Triticeae.

Identification of a microsatellite on chromosome 7B showing a strong linkage with yellow pigment in durum wheat (Triticum turgidum L. var. durum)

Abstract: The objective of this study is to identify QTLs linked to yellow pigment content in durum wheat. A durum-dicoccoides genetic linkage map was constructed using 124 microsatellites, 149 amplified fragment length polymorphism (AFLPs), and six seed storage proteins (SSP) in a population of 114 recombinant inbred lines (F8). The population has been obtained from a cross between a durum cultivar Omrabi5 and Triticum dicoccoides600545 and backcrossed to Omrabi5. The map consists of 14-durum chromosomes plus an unknown group; and shows a good synteny to the previously published wheat maps. Yellow pigment was measured in the population in three different locations during 3 seasons. Analysis of QTLs was based on simple and simplified composite interval mapping (SIM and sCIM). Three QTLs for yellow pigment were detected on the chromosomal group 7 (7AL and 7BL telomeres) explaining 62% of the total variation. On 7BL, a major microsatellite (Xgwm344) explained by itself 53%, whereas on 7AL, the other two QTLs have contributed 13 and 6%. All determined QTLs showed a strong genetic effect and a weak QTL x E effect. The QTLs effect was consistent across all environments and showed a large effect. Consequently, promising QTLs will be used in the marker assisted breeding program to enhance the selection efficiency for yellow pigment.

The List of the Chromosome Races of the Common Shrew (Sorex Araneus)

Abstract: The list of chromosome races of the common shrew (Sorex araneus) was compiled, the vast literature has been scrutinized, and unpublished data have been added. Altogether, 50 chromosome races could be listed. The name and its synonyms, chromosomal constitution, author of the description, type locality, known distribution range, and additional information are reported for individual races. The present list should be considered a working document that will be regularly updated and supplemented.

Marker‐assisted pyramiding of brown planthopper (Nilaparvata lugens Stål) resistance genes Bph1 and Bph2 on rice chromosome 12

Abstract: Brown planthopper (BPH) (Nilaparvata lugens Stal) is a significant insect pest of rice (Oryza sativa L.). We constructed a gene-pyramided japonica line, in which two BPH resistance genes Bph1 and Bph2 on the long arm of chromosome 12 independently derived from two indica resistance lines were combined through the recombinant selection. The gene-pyramiding was achieved based on the previously constructed high-resolution linkage maps of the two genes. Two co-dominant and four dominant PCR-based markers flanking the loci were used to select for a homozygous recombinant line in a segregating population that was derived from a cross between the parental homozygous single-gene introgression lines. BPH bioassay showed that the resistance level of the pyramided line was equivalent to that of the Bph1-single introgression line, which showed a higher level of resistance than the Bph2-single introgression line. The pyramid line should provide a useful experimental means for studying the fine structure of the chromosomal region covering these two major BPH resistance genes.

Phenotypic Diversity of Ethiopian Barleys in Relation to Geographical Regions, Altitudinal Range, and Agro-Ecological Zones: As an Aid to Germplasm Collection and Conservation Strategy

Abstract: Data on 51 accessions of landrace barley from an Ethiopian collection were analyzed for variation of six morphological traits. Shannon- Weaver diversity indices (H′) were calculated for traits, populations, geographical regions, altitude classes, and agro-ecological zones. Mean diversity (H′) for Ethiopia was 0.71 ± 0.09. Polymorphism was high for rachilla hair type (H′= 0.92) and aleurone color (H′= 0.90) and relatively low for some traits, e.g., caryopsis type (H′= 0.29). The chi-square (x2) analysis displayed that some regions, such as Welega, Tigray, Gojam, had significant phenotypic differences for most traits. Analysis of variance showed no significant differences either among regions (except aleurone color) or among altitude classes as well as among agro-ecological zones but attributed most of the variance to populations. A clinal pattern of variation was observed in rachilla hair type and row number with altitude, the latter also in relation to north-south direction. The highest mean diversity index (H′= 0.77 ± 0.07) was recorded for areas ranging in altitude from 2000 to 2500 m. A decline in mean diversity with increasing elevation was also noted. Although no obvious patterns of diversity with respect to major agro-ecological zones were revealed, zones with fairly high estimates of variations (H′= 0.74 ± 0.11) were identified. Principal components analyses showed that 28% of the variance was explained by black lemma/blue aleurone/black seed and white phenotype and further corroborated character correlations revealed by diversity indices. Based on the characters considered and populations evaluated, sites in Gonder/Tigray (representing the north), Welega (in the western), and Arsi (representing central and eastern regions), with due consideration to agro-ecological and altitudinal parameters, may serve as appropriate locations for in situ conservation.

Analysis of Genetic Diversity in Geographically Structured Populations: A Bayesian Perspective

Abstract: Bayesian approaches have been widely applied to partitioning diversity within and among levels in many different multi-level modeling contexts. In spite of the structural similarities between these Bayesian models and hierarchical approaches to partitioning diversity in population genetics, population geneticists have not explored the use of hierarchical Bayesian models to provide estimates of Wright's F-statistics. In this paper I describe and illustrate the application of a simple multilocus, two-allele model sufficient for partitioning diversity within and among populations. Extenions of the model incorporate both fixed-effect and random-effect models of population sampling at multiple hierarchical levels with multiple alleles per locus. The Bayesian approach developed here is closely related to previously developed methods for likelihood analysis of the same problem. I illustrate the utility of the Bayesian approach with a reanalysis of previously published allozyme data from Argania spinosa.

Molecular estimates of primate divergences and new hypotheses for primate dispersal and the origin of modern humans.

Abstract: The concept of recent hominoid divergences has been a mainstay in molecular primatology since the 1970's. However, the ages allocated to the calibration points used to establish these divergence times and the estimates resulting from their application, notably the commonly accepted divergence between Pan (chimpanzees) and Homo 5 million years before present (MYBP), are now palaeontologically refutable. Here we estimate the ages of various primate divergences using three references with a more detailed fossil record than any of the traditional primate calibration points. Our findings suggest that the latter yield datings that are too recent by a factor of about two. For example, our estimates place the divergence between Pan and Homo 10.5-13 MYBP. The revised estimates of primate divergence times suggest a new hypothesis for primate evolution and dispersal: that the divergence between strepsirhines (lorises, lemurs) and anthropoids was contemporary with the break-up of Southern continents about 90 MYBP, with strepsirhines becoming isolated on Madagascar and later dispersing to Africa (and Asia) and anthropoids evolving in South America and subsequently colonizing Africa (and Asia), or possibly North America. In addition we present a new hypothesis, which accommodates the strikingly similar coalescence times for human mitochondrial DNA and the Y-chromosome. This hypothesis posits a common mitochondrial and Y-chromosome bottleneck about 400,000 years ago, associated with the origination of the human 2n = 46 karyotype, obstructing genetic exchange with the 2n = 48 Homo contemporaries.

Chromosomal Rearrangement in Autotetraploid Plants of Arabidopsis Thaliana

Abstract: Recent development of cytogenetic techniques has facilitated significant progress in Arabidopsis thaliana karyotype studies. Double-target FISH with rRNA genes provides makers that allow individual chromosome in the genome to be distinguished. Those studies have revealed that the number and position of rDNA loci is ecotype-specific. Arabidopsis is believed to be a true diploid (x = 5) with numerous ecotypes (accessions) and only a very few natural polyploid populations reported. Few studies were undertaken to induce polyploidy in Arabidopsis, however none of those gave the cytogenetic characteristics of polyploid plants. Our analysis of chromosome pairing of colchicine-induced autotetraploid Arabidopsis (Wilna ecotype) revealed preferential bivalent pairing in PMCs (pollen mother cells). In order to attempt to explain this phenomenon, first of all more detailed cytogenetic studies of autopolyploid plants have been undertaken. The localization of 45S and 5S rDNA loci in the diploid and autotetraploid plants revealed that Wilna ecotypes belongs to the group of Arabidopsis accessions with only two 5S rDNA loci present in a genome. Furthermore, the rearrangement of 45S rDNA locus in autopolyploid, when compared to the diploid plants of the same ecotype, was revealed. These results are interesting also in the context of the recently emphasised role of polyploidy in plant evolution and speciation. Arabidopsis, despite having small chromosomes, is a good system to study chromosome behaviour in relation to diploidization of autopolyploids and to evaluate the degree of chromosomal rearrangements during this process.

Molecular mapping in tropical maize (Zea mays L.) using microsatellite markers. 2. Quantitative trait loci (QTL) for grain yield, plant height, ear height and grain moisture.

Abstract: A previous genetic map containing 117 microsatellite loci and 400 F(2) plants was used for quantitative trait loci (QTL) mapping in tropical maize. QTL were characterized in a population of 400 F(2:3) lines, derived from selfing the F(2) plants, and were evaluated with two replications in five environments. QTL determinations were made from the mean of these five environments. Grain yield (GY), plant height (PH), ear height (EH) and grain moisture (GM) were measured. Variance components for genotypes (G), environments (E) and GxE interaction were highly significant for all traits. Heritability was 0.69 for GY, 0.66 for PH, 0.67 for EH and 0.23 for GM. Using composite interval mapping (CIM), a total of 13 distinct QTLs were identified: four for GY, four for PH and five for EH. No QTL was detected for GM. The QTL explained 32.73 % of the phenotypic variance of GY, 24.76 % of PH and 20.91 % of EH. The 13 QTLs displayed mostly partial dominance or overdominance gene action and mapped to chromosomes 1, 2, 7, 8 and 9. Most QTL alleles conferring high values for the traits came from line L-14-4B. Mapping analysis identified genomic regions associated with two or more traits in a manner that was consistent with correlation among traits, supporting either pleiotropy or tight linkage among QTL. The low number of QTLs found, can be due to the great variation that exists among tropical environments.

Estimates of broad-sense heritability for seed yield and yield criteria in faba bean (Vicia faba L.)

Abstract: Eight faba bean (Vicia faba L.) genotypes were grown at lowlands of the west-Mediterranean region of Turkey in order to estimate the broad-sense heritability for plant height, number of stems and pods per plant, seed yield, biological yield, 100-seed weight, days to flowering and maturity. The heritability for plant height, number of stems and pods per plant, seed yield, biological yield, 100-seed weight, days to flowering and maturity were estimated as 83%, 63%, 43%, 62%, 52%, 99%, 97% and 97%, respectively. It was found that seed weight was the least affected trait across changing environmental conditions and followed by days to flowering and maturity. On the other hand, number of pods per plant, biological and seed yields and number of stems per plant were the most affected traits versus environmental conditions.

Combining ability in the F1 and F2 generations of diallel cross in hexaploid wheat (Triticum aestivum L. em. Thell).

Abstract: The F(1) and F(2) progenies of a ten-parent diallel cross (excluding reciprocals) of hexaploid wheat (Triticum aestivum L. em. Thell) were analyzed for combining ability for quantitative and quality traits. The results indicated significant differences among the parents for general combining ability (gca) and crosses for specific combining ability (sca) for all the characters studied. The gca and sca components of variance were significant for all the traits. However, the gca component of variance was predominant indicating the predominance of additive gene effects for the traits studied. Among the parents Durgapura 65, HD 2285, Lok-1, Raj 1972 and HD 2329 were the best general combiners for grain yield and average to high combiners for tillers per plant, grain yield per spike, grains per spike and 1000-grain weight. The best specific crosses for grain yield were Sonalika x WH 157, HD 2428 x Durgapura 65, Durgapura 65 x Sonalika, HD 2428 x Lok-1 and CPAN 3004 x Raj 1972. The parent Raj 1972, Lok-1 and HD 2285 were the best general combiners for grain yield and protein content, however, Raj 3077 was the best general combiner for protein content. The most suitable specific crosses for protein content were HD 2329 x HD 2285, HD 2428 x Raj 1972 and CPAN 3004 x WH 157. Most of the specific crosses for grain yield as well as protein content involved high x average, average x average and average x poor general combiners. To ensure further increase in grain yield along with high protein, combinations of desirable yield components is advocated. Inclusion of F(1) hybrids showing high sca and having parents with good gca, into multiple crosses and/or bi-parental mating, or diallel selective mating could prove a worthwhile approach for further improvement of grain yield in bread wheat.

Genetic Control of Flavonoid Biosynthesis in Barley

Abstract: Mutations in genes associated with the pathway of flavonoid biosynthesis can readily be induced in barley and since 1977 more than 700 mutants have been isolated in which the biosynthesis of anthocyanin and/or proanthocyanidin is affected. Diallelic crosses have localized a majority of the mutants to 28 different complementation groups (Ant genes). Mutations in ten of the Ant genes result in a blocked synthesis of proanthocyanidins in the testa layer of the grains, whereas mutations in 18 Ant gene loci only affect anthocyanin synthesis in various organs of the plants. Seven Ant genes have been localized to a chromosome. A number of investigations have been carried out to characterize the ten known Ant genes acting on the biosynthesis of proanthocyanidins. Grains of mutants in different Ant genes and wildtypes were analyzed for contents of flavonoids and other phenolic compounds and the activity levels of several of the enzymes in the flavonoid pathway were studied. The gene locus Ant 18 has been isolated both in the form of cDNA and genomic clones. Ant 17, Ant 18, Ant 19, Ant 22, and Ant 26 are structural genes. Ant 13 is a regulatory gene coding for a transcription factor necessary for transcription of at least three structural genes in the flavonoid pathway. The action of the genes Ant 21, Ant 25, Ant 27, and Ant 28 is not fully understood. They might be regulatory genes.

Microsatellite Markers for Paternity Testing in the Willow Warbler Phylloscopus Trochilus: High Frequency of Extra‐Pair Young in an Island Population

Abstract: Four microsatellite markers from the willow warbler Phylloscopus trochilus: were isolated and characterised. The combined exclusion probability of the three most polymorphic markers (Phtr1, Phtr2 and Phtr3) was 0.96. These markers were used to test for the occurrence of extra-pair young (EPY) in twelve willow warbler families sampled from the island of Gotland in 1992 and 1993. The mean frequency of extra-pair young was found to be 28% and the mean frequency of families with extra-pair young 58%. These results contrast with an earlier study in a mainland Swedish population, where no EPY were found. The island population in this study has a higher breeding density than the mainland population, rendering support for density dependent factors affecting the frequency of EPY. A cross-species study showed that the willow warbler microsatellite markers can also be used in other European passerines as well as distantly related species, such as the Australian magpie Gymnorhina tibicen.

The benefits of increasing the number of microsatellites utilized in genetic population studies: an empirical perspective.

Abstract: One of the key issues concerning the application of microsatellite DNA data in evolutionary studies is how the number of loci applied may influence the stability of genetic distances and corresponding phylograms. While computer simulations have suggested that over 30 microsatellites are required for accurate evolutionary inference, we show that a median of only six loci have been generally applied in studies of wild populations. Factors contributing to this contrast include: i) uncertainty regarding the potential benefits that can be gained from a realistic increase in the number of loci used; and ii) the lack of empirical studies assessing the influence of the number of microsatellites on the reliability of genetic distance estimation and phylogeny construction. In order to address these issues, we applied resampling techniques to microsatellite data in widely distributed populations of European grayling (Thymallus thymallus, Salmonidae). In agreement with expectations based on simulated data, we demonstrate empirically that the stability of commonly used genetic distances (DCE, DA and (deltamu)2) and the corresponding neighbor-joining phylograms is positively associated with the number of microsatellites utilized. For instance, increasing the number of loci from six to 17 resulted in a striking 75% increase in the proportion of DCE phylogram nodes supported by a bootstrap estimate of over 70%. Our results demonstrate that even moderately increasing the number of loci can be very beneficial--a finding extremely relevant for studies of natural populations for which optimally high microsatellite numbers are out of reach. Furthermore, the number of loci most commonly used to date may lead to erroneous inference of the evolutionary relationships between populations.

Analysis of Applications DNA from Old Scale Samples: Technical Aspects, and Perspectives for Conservation

Abstract: Collections of old scales from salmonid fishes can be found in many fisheries institutions in Europe and North America. Such scales have been shown to be useful as a source of DNA, which can be used for analysis of microsatellites. We here describe the technical procedures in relation to extraction and PCR amplification of DNA from old scales. Further, we describe case stories of the application of old scale DNA analysis for conservation genetics with regard to: 1) Identification of native populations, 2) assessment of loss of genetic variation, 3) estimation of effective population size, 4) evaluation of anthropogenic effects on the genetic population structure/mode of migration and 5) the temporal stability of the genetic population structure. Finally, we describe the perspectives for future genetic studies using old scale DNA. In particular, we evaluate other types of genetic markers such as mtDNA and loci subjected to selection, in association with old scale DNA, as tools for prioritising populations for conservation. E. E. Nielsen, Danish Institute fbr Fisheries Research, Departmeni qf Inland Fisheries, 8600 Silkeborg, Denmark. E-mail:

Chromosomes and their Meiotic Behavior in Two Families of the Primitive Infraorder Dipsocoromorpha (Heteroptera)

Abstract: Five species belonging to the two families of Dipsocoromorpha were studied: three species from the family Dipsocoridae—Cryptostemma pusillimum J. Sb. (2n = 16 + 2m + XY1, Y2), C. hickmani Hill (2n = 18 + 2m + XY), and C. castaneovitreus Linnavuori (2n = 18 + 2m + XY) and two species from the family Schizopteridae Pateena elimala Hill (2n = 30+ 2m + XO) and Rectilamina australis Hill (2n = 30 + 2m + XO). In all species, autosomes formed chiasmate bivalents in spermatogenesis, and the sex chromosome univalent(s) divided at the first meiotic division and segregated at the second. The evolution of autosomal number, m-chromosomes, and sex chromosome systems within the Dipsocoromorpha and in the whole Heteroptera was discussed.

Geographical Patterns of Morphological Variation in Sorghum (Sorghum Bicolor (L.) Moench) Germplasm from Ethiopia and Eritrea: Qualitative Characters

Abstract: Summary A total of 415 sorghum (Sorghum bicolor (L.) Moench) accessions representing different regions of Ethiopia, Eritrea and a group of introduced lines were evaluated for 15 quantitative characters to determine the extent and geographical pattern of morphological variation. The extent of variation was highly pronounced for agronomically important characters for sorghum. These characters included plant height, days for 50% flowering, peduncle exsertion, panicle length and width, number and length of primary branches per panicle and thousand seed weight. Significant regional variation was also observed for most of the characters. The results implied that environmental factors such as altitude, rainfall, temperature and growing period are important in regional variation. Mean for plant height and for days for 50% flowering showed clinal variation along the gradients of rainfall pattern and growing period in Ethiopia. Moreover, there were significant positive correlation coefficients between most of the characters. This included the correlation between agronomic characters of primary interest in sorghum breeding such as plant height and days for 50% flowering and also between various characters and the altitude of the collection sites. The implications of the results in plant breeding, germplasm collection and conservation as well as the probable sources of the wide range of variation are discussed.

The “Minimal Essential MHC” Revisited: Both Peptide‐Binding and Cell Surface Expression Level of MHC Molecules are Polymorphisms Selected by Pathogens in Chickens

Abstract: Birds, like mammals, have a highly polymorphic MHC that determines strong allograft rejection. However, in contrast to mammals, there are a number of viral diseases for which resistance and susceptibility are determined by particular chicken MHC haplotypes. We have found that certain common chicken MHC haplotypes express only one class I molecule at high levels. The selection on a single MHC gene should be strong, in contrast to the situation in mammals. We have determined the peptide motifs for the dominant class I molecules from a number of chicken MHC haplotypes and found that they can explain the outcome of infections with a small virus. However, the strongest MHC association is the resistance of the chicken B21 haplotype to classical Marek's disease virus, a relatively large pathogen for which any MHC molecule should find peptides. In 40 chicken lines, the level of class I expression correlates with the level of MHC-determined susceptibility to Marek's disease, the most susceptible B19 with the highest expression and the most resistant B21 with the lowest expression. Thus, cell surface expression level of class I molecules appears to be a polymorphism under selection by infectious pathogens, just like peptide-binding specificity. We speculate that these expression level differences are another manifestation of the simple MHC of chickens, which in human and mouse haplotypes are averaged out.