bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating variance components and heritabilities in the wild: a case study using the ‘animal model’ approach
Authors: Milner  , Pemberton  , Brotherstone  , Albon
Published: March 2003

Using a genealogy containing over 1800 dams and nearly 400 sires (estimated by genetic paternity techniques), combined with maximum likelihood procedures and an ‘animal model’, we have estimated the heritabilities, genetic correlations and variance components of three morphometric traits in the Soay sheep (Ovis aries) on St Kilda, Scotland. This approach allows heritabilities to be estimated in natural populations that violate the assumptions of offspring–parent regression methods. Maternal (or paternal) effects can also be estimated under natural conditions. We demonstrate that all the traits, body weight, hind leg length and incisor arcade breadth, have low but significant heritabilities. Body weight, the trait that experiences the strongest selection, had the lowest heritability but the highest additive genetic coefficient of variation. An evolutionary response to selection is predicted. When maternal effects were not taken into consideration heritabilities were over-estimated, although this effect was only significant in female offspring.
Immunoglobulin plasma concentration in relation to egg laying and mate ornamentation of female barn swallows (Hirundo rustica)
Authors: Saino N. , Martinelli R. , Møller A. P.
Published: March 2003

In vertebrates, offspring have a relatively inefficient immune system soon after birth. Female birds transmit immunoglobulins to the egg, which can confer protection against parasites to their offspring after hatching, but allocation of immune factors can depend on the reproductive value of the offspring as affected, for example, by the quality of their father. We analyse the variation in immunoglobulin levels of female barn swallows (Hirundo rustica) during the breeding cycle in relation to the expression of a secondary sexual character of their mates. Circulating immunoglobulins peaked on approximately the day before that of laying of their first egg, but postlaying concentration was similar to the concentration well before laying. Immunoglobulin levels per unit volume of plasma were lower for females breeding late compared with those breeding early. Haematocrit of females reached an absolute minimum on the day of laying of the third egg. In males, concentration of immunoglobulins relative to other plasma proteins did not change in relation to the breeding stage. Smaller relative concentrations of immunoglobulins and haematocrit were observed in males breeding late in the season. Immunoglobulin concentration of females was positively correlated with the level of ornamentation of their mates. These results suggest that females alter their immune profile to transmit humoral factors providing immune defence against pathogens to their offspring after hatching. This enhancement of immune protection is larger when the offsprings are of relatively large reproductive value as when sired by high quality males. Alternatively, females with relatively large immunoglobulin concentration preferentially mate with the most ornamented males.
Resource allocation in the red ant Myrmica ruginodis– an interplay of genetics and ecology
Authors: Walin L. , Seppä P.
Published: March 2003

Worker-queen conflicts over reproductive allocation (colony maintenance vs. reproduction) and sex allocation (females vs. males) were examined in two populations of the facultatively polygynous ant Myrmica ruginodis. Plasticity of social organization in the form of two co-existing social types (microgyna and macrogyna) has a profound effect on reproductive allocation. Workers control sex allocation by biasing sex ratios towards their own interest, but local resource competition (LRC) because of restricted dispersal of microgyna females resulted in male bias in one study population. Colony sex ratios were split and followed the predictions of the split sex ratio theory: single queen colonies with higher relatedness asymmetry (RA) produced more females than multiple queen colonies with lower RA. Single and multiple queen colonies showed similar patterns in most aspects of their reproduction, and reproductive allocation could not be explained by the hypothesis tested. This suggests that reproductive allocation conflict is of minor importance in M. ruginodis.
The genic view of the process of speciation
Authors: Wu Chung-I
Published: March 2003

The unit of adaptation is usually thought to be a gene or set of interacting genes, rather than the whole genome, and this may be true of species differentiation. Defining species on the basis of reproductive isolation (RI), on the other hand, is a concept best applied to the entire genome. The biological species concept (BSC; Mayr, 1963) stresses the isolation aspect of speciation on the basis of two fundamental genetic assumptions – the number of loci underlying species differentiation is large and the whole genome behaves as a cohesive, or coadapted genetic unit. Under these tenets, the exchange of any part of the genomes between diverging groups is thought to destroy their integrity. Hence, the maintenance of each species’ genome cohesiveness by isolating mechanisms has become the central concept of species. In contrast, the Darwinian view of speciation is about differential adaptation to different natural or sexual environments. RI is viewed as an important by product of differential adaptation and complete RI across the whole genome need not be considered as the most central criterion of speciation. The emphasis on natural and sexual selection thus makes the Darwinian view compatible with the modern genic concept of evolution. Genetic and molecular analyses of speciation in the last decade have yielded surprisingly strong support for the neo-Darwinian view of extensive genetic differentiation and epistasis during speciation. However, the extent falls short of what BSC requires in order to achieve whole-genome ‘cohesiveness’. Empirical observations suggest that the gene is the unit of species differentiation. Significantly, the genetic architecture underlying RI, the patterns of species hybridization and the molecular signature of speciation genes all appear to support the view that RI is one of the manifestations of differential adaptation, as Darwin (1859, Chap. 8) suggested. The nature of this adaptation may be as much the result of sexual selection as natural selection. In the light of studies since its early days, BSC may now need a major revision by shifting the emphasis from isolation at the level of whole genome to differential adaptation at the genic level. With this revision, BSC would in fact be close to Darwin’s original concept of speciation.
Kin structure and queen execution in the Argentine ant Linepithema humile: M. REUTER ET AL.
Authors: Reuter M. , Balloux F. , Lehmann L. , Keller L.
Published: March 2003

Every spring, workers of the Argentine Ant Linepithema humile kill a large proportion of queens within their nests. Although this behaviour inflicts a high energetic cost on the colonies, its biological significance has remained elusive so far. An earlier study showed that the probability of a queen being executed is not related to her weight, fecundity, or age. Here we test the hypothesis that workers collectively eliminate queens to which they are less related, thereby increasing their inclusive fitness. We found no evidence for this hypothesis. Workers of a nest were on average not significantly less related to executed queens than to surviving ones. Moreover, a population genetic analysis revealed that workers were not genetically differentiated between nests. This means that workers of a given nest are equally related to any queen in the population and that there can be no increase in average worker–queen relatedness by selective elimination of queens. Finally, our genetic analyses also showed that, in contrast to workers, queens were significantly genetically differentiated between nests and that there was significant isolation by distance for queens.
Laboratory environments are not conducive for allopatric speciation
Authors: Florin A.-B. , Ödeen A.
Published: March 2003

We review published records of laboratory experiments on peripatric and vicariance allopatric speciation to address the following three questions: (1) What was the true effect size of reproductive isolation? (2) Was the reproductive isolation persistent? (3) What influenced the development of isolation? Contrary to popular belief, laboratory evidence for allopatric speciation is quite weak. Assortative mating was only found among derived populations in vicariance experiments. Reproductive isolation against control populations was only intermittent, so there is reason to doubt if some cases showing significant reproductive isolation really should be attributed to speciation. The method of testing was at least as important as the speciation model. Experimental populations tested against each other were the most likely to demonstrate reproductive isolation. This study suggests that allopatric speciation experiments are more likely to yield conclusive results under divergent selection than under drift, and points to the benefits of large populations and many generations.
Evolutionary dynamics of a selfishly spreading gene that stimulates sexual reproduction in a partially sexual population
Authors: Johnson L. J. , Brookfield J. F. Y.
Published: March 2003

The ability of selfishly spreading DNA sequences to invade host populations is intimately bound up with sex. In the absence of sexual reproduction, an element that lowers the fitness of its host and which is initially found in only some of the population will inevitably be lost by natural selection. This will occur even if the element can spread selfishly in the genomes of those individuals which initially possessed it. Here, we create a model in which such a gene is introduced into a population in which individuals sometimes reproduce sexually and sometimes asexually. The element can raise the level of sexuality in its bearers. There is selection against those individuals with the gene (i.e. it is selfish), and a further selective cost to sexual reproduction. The dynamics of the model that arises from these simple assumptions are remarkably complex, with fixation or loss of the selfish gene, unstable and stable equilibria, and effective neutrality all being possible dependent on the parameter values. A selfish gene that increases the level of sexuality of its bearers will tend to have a higher likelihood of invading a host population, and faster spread, but a lower likelihood of spreading to fixation, than an equivalent gene with no effect on sex.
Control of male production in the swarm-founding wasp, Polybioides tabidus
Authors: Henshaw M. T. , Queller D. C. , Strassmann J. E.
Published: March 2003

In social insect colonies, male production may involve conflicts over the sex ratio, worker vs. queen reproduction, and each queen's contribution to the males when there are multiple queens. We examined male production in the swarm-founding, multiple-queened wasp, Polybioides tabidus, for which previous work suggested worker control of the sex ratios. We found that queens produced the males in accord with the collective worker preference. We also found that diploid males were produced, but only in association with haploid males. Simulations show they should have been produced in other colonies as well and their absence indicates that they were killed in some of these other colonies. The pattern of their removal indicates that P. tabidus cannot distinguish diploid from haploid males, and that haploid males would have been removed from these colonies too. This provides evidence that the workers are able to manipulate male production when collective preferences dictate.
A gene's eye view of epistasis, selection and speciation
Authors: Wade M. J.
Published: March 2003

In this mini-review, I discuss the effects of gene interaction or epistasis from a `gene's eye view.' By a `gene's eye view' of epistasis, I mean that I will consider a single, bi-allelic locus, A, whose effects on fitness result only from its interactions with alleles of another, unknown locus, X. I will show how changes in the frequencies of alleles at the background locus affect the relationship of alleles at the A-locus to fitness. Changing the genetic background changes the fundamental characteristics of the A-locus, such as the magnitude and sign of allelic effects on fitness, and, consequently, it changes the strength and pattern of selection. I consider each of the four kinds of pair–wise interactions between two loci and show that some kinds of epistasis are more sensitive than others to population genetic subdivision. Lastly, I show that some kinds of epistasis are more likely than others to affect the process of speciation and contribute to or be responsible for general genetic features of interspecific hybrids, such as Haldane's rule.
No evidence for parallel sympatric speciation in cichlid species of the genus Pseudotropheus from north-western Lake Malawi
Authors: Rico C. , Bouteillon P. , Van Oppen M. J. H. , Knight M. E. , Hewitt G. M. , Turner G. F.
Published: March 2003

To test the hypothesis of parallel speciation by sexual selection, we examined length variation at six microsatellite loci of samples from four sites of four to six putative species belonging to two subgenera of rocky shore mbuna cichlids from Lake Malawi. Almost all fixation indices were significantly different from zero, suggesting that there is presently little or no gene flow among allopatric populations or sympatric species. Analysis of variance indicated that genetic distances among allopatric populations of putative conspecifics were significantly lower than among sympatric populations of heterospecifics. The topology of trees based on distance matrices was also largely consistent with the hypothesis that the putative species are monophyletic and have thus not evolved in parallel in their present locations. If parallel speciation does occur in Malawi cichlids, it may be on a larger spatial scale than investigated in our study.
Frequency dependence in matings with water-borne sperm
Authors: Pemberton A. J. , Noble L. R. , Bishop J. D. D.
Published: March 2003

Negative frequency-dependent mating success – the rare male effect – is a potentially powerful evolutionary force, but disagreement exists as to whether previous work, focusing on copulating species, has robustly demonstrated this phenomenon. Noncopulating sessile organisms that release male gametes into the environment but retain their eggs for fertilization may routinely receive unequal mixtures of sperm. Although promiscuity seems unavoidable it does not follow that the resulting paternity obeys ‘fair raffle’ expectations. This study investigates frequency dependence in the mating of one such species, the colonial ascidian Diplosoma listerianum. In competition with an alternative sperm source males fathered more progeny if previously mated to a particular female than if no mating history existed. This suggests positive frequency-dependent selection, but may simply result from a mate order effect involving sperm storage. With fewer acclimation matings, separated by longer intervals, this pattern was not found. When, in a different experimental design, virgin females were given simultaneous mixtures of gametes at widely divergent concentrations, sperm at the lower frequency consistently achieved a greater than expected share of paternity – a rare male effect. A convincing argument as to why D. listerianum should favour rare sperm has not been identified, as sperm rarity is expected to correlate very poorly with ecological or genetic male characteristics in this pattern of mating. The existence of nongenetic female preferences at the level of colony modules, analogous in effect to fixed female preferences, is proposed. If visible to selection, indirect benefits from increasing the genetic diversity of a sibship appear the only likely explanation of the rare male effect in this system as the life history presents virtually no costs to multiple mating, and a near absence of direct (resource) benefits, whereas less controversial hypotheses of female promiscuity (e.g. trade up, genetic incompatibility) do not seem appropriate.
Differential strength of sex-biased hybrid inferiority in impeding gene flow may be a cause of Haldane's rule
Authors: Wang Ren-Xue
Published: March 2003

In animals, if one sex of the F1 hybrid between two species is sterile or inviable, it is usually the heterogametic (XY or WZ) sex. This phenomenon, known as Haldane's rule, is currently thought to be coincidentally caused by different mechanisms in separate entities. The following questions have never been asked: Are heterogametic and homogametic inferiority (sterility or inviability) equivalent as isolating mechanisms? Could discrepancies between them, if existing, produce Haldane's rule? Here I consider sex-biased hybrid inferiority strictly as an isolating mechanism, and quantitatively evaluate its strength in impeding gene flow. The comparison reveals that the ability of sex-biased inferiority to impede gene flow varies according to the sex and chromosome involved. Heterogametic inferiority is a weaker barrier when unidirectional and a much stronger one when in compound reciprocal directions, compared with homogametic inferiority. Such differential strength may affect divergence in speciation and produce Haldane's rule.
Tumour immunotherapy: new tools, new treatment modalities and new T‐cell antigens
Authors: Schultze J. L. , Maecker B. , Von Bergwelt‐Baildon M. S. , Anderson K. S. , Vonderheide R. H.
Published: March 2003

Tumour immunology has seen many exciting developments in the last few years. In addition to tumour antigens that are defined by antitumour T‐ and B‐cell responses in patients, the human telomerase reverse transcriptase has been identified by ‘reverse immunology’ as the first truly universal tumour antigen. Molecular remission has been associated with a cancer vaccine that targets the clonal idiotype of B‐cell malignancies, and sophisticated cellular vaccines (including fusions of tumour cells and antigen‐presenting cells) have demonstrated promising results. Moreover, our capabilities of measuring immunity have been significantly enhanced by novel technology, such as major histocompatibility complex (MHC)–peptide tetramers and ELISPOT analysis. We are now capable of tracking antigen‐specific T cells at a single cell level. This review will analyse recent developments and highlight some important issues that need to be addressed in the future.
Blood donors infected with the hepatitis B virus but persistently lacking antibodies to the hepatitis B core antigen
Authors: Laperche S. , Guitton C. , Smilovici W. , Courouce A. M.
Published: March 2003

Background and objectives

Antibodies to the core of hepatitis B virus (anti‐HBc) are considered to be the best serologically reliable markers of hepatitis B virus (HBV) infection. Through a national epidemiological survey, two young and first‐time blood donors, originating from HBV‐endemic areas, were identified as HBV carriers with an absence of anti‐HBc reactivity.

Materials and Methods

We followed up these two subjects in order to investigate the evolution of their HBV serological profiles. Nucleotide sequencing was performed of the entire pre‐C/C region of the strains infecting these donors.

Results

The same serological profile of active viral replication with an apparent persistent lack of anti‐HBc and normal alanine aminotransferase (ALT) levels was found for both subjects throughout a follow‐up of 19 months and 4 months, respectively. Neither donor was immunocompromised. Nucleotide sequence analysis of the pre‐C/C region did not show mutations or deletions in encoded proteins.

Conclusion

The hypothesis of an in utero HBV infection responsible for an immune tolerance to HBV seems to be the most probable explanation for this particular immunological situation. Such occurrences in the blood donor population are probably rare as less than 0·1% of hepatitis B surface antigen (HBsAg)‐positive donors exhibit such a profile, in our experience. Moreover, this phenomenon does not impose a risk of HBV transmission by blood donation, as the exclusion of HBV‐infected blood donation is based on HBsAg detection. However, such a risk might be encountered with the hepatitis C virus (HCV) for which at present only antibodies to HCV are screened.
Collaborative study to calibrate hepatitis C virus genotypes 2–6 against the HCV International Standard, 96/790 (genotype 1)
Authors: Saldanha J. , Heath A. ,   Collaborative Study Group
Published: March 2003

Background and ObjectivesA major requirement of a hepatitis C virus (HCV) RNA nucleic acid amplification technology (NAT) assay validation is the ability of the assay to detect the six major genotypes of HCV with equivalent sensitivities. The aim of this study was to characterize and calibrate an HCV genotype panel for use in such studies.

Materials and MethodsPanels consisting of the first International Standard (IS) for HCV RNA NAT assays (96/790; HCV genotype 1a) and isolates of genotypes 2–6 were sent to 17 laboratories worldwide which use a variety of NAT tests, both qualitative and quantitative. The HCV RNA content of each panel member was determined and the mean titre calculated in International Units/ml (IU/ml).

ResultsThe calculated mean titres (calibrated against the HCV International Standard), in log10IU/ml, of the genotype 2–6 samples were 3·99, 3·81, 4·14, 4·18 and 4·61, respectively.

ConclusionsAn HCV genotype panel, calibrated in IU/ml, has been established and should be valuable for assay validation. All the genotypes were detected by all the assays used, but it was not possible to demonstrate that the genotypes were detected with equal efficiencies.
Effect of Integrated Use of Farmyard Manure and Sulphur in a Soybean and Wheat Cropping System on Nodulation, Dry Matter Production and Chlorophyll Content of Soybean on Swell‐Shrink Soils in Central India
Authors: Ganeshamurthy A. N. , Sammi Reddy K.
Published: March 2003

In a 3‐year experiment on a Typic Haplustert low in soil test sulphur (S), the response to applied farmyard manure (FYM) and S was studied in terms of the nodule production, nodule dry weight, chlorophyll content, dry matter production and seed yield of soybean. FYM was applied to soybean at four levels (0–16 t ha−1). S as gypsum was also applied at four levels (0–60 kg ha−1) to both soybean and wheat every year. Both total and active nodule production, nodule dry weight, dry matter production and seed yield of soybean were increased significantly by the application of both FYM and S. However, the proportion of total nodules to active nodules fell sharply for applications higher than 8 t FYM and 40 kg S ha−1.
Water Stress Tolerance of Wheat (Triticum aestivum L.): Variations in Hydrogen Peroxide Accumulation and Antioxidant Activity in Tolerant and Susceptible Genotypes
Authors: Sairam R. K. , Srivastava G. C.
Published: March 2003

An experiment was conducted on five wheat (Triticum aestivum L.) cultivars, C 306, PBW 175 (tolerant to water stress), DL 153‐2 (moderately tolerant to water stress), HD 2428 and HD 2329 (recommended for irrigated conditions, susceptible to water stress), under pot culture conditions to study the effect of water stress on oxidative injury and antioxidant activity. Water stress significantly decreased relative water content (RWC), ascorbic acid content and membrane stability, and increased hydrogen peroxide and malondialdehyde content, a measure of lipid peroxidation, and activities of antioxidant enzymes in all the genotypes at 7, 17 and 27 days after anthesis (DAA). Water stress tolerant genotypes C 306 and PBW 175, closely followed by DL 153‐2, were superior to HD 2428 and HD 2329 in maintaining high RWC, ascorbic acid content and membrane stability and lower hydrogen peroxide content and lipid peroxidation (malondialdehyde content) under water stress at the three stages. The highest activities of glutathione reductase and catalase under water stress were observed in C 306, PBW 175 and DL 153‐2 and the lowest activities in HD 2428 and HD 2329 at all the stages. Superoxide dismutase activity at all stages under irrigated conditions and at the first and second stages under water stress conditions did not show significant variation among the different genotypes, but at the last stage under water stress the enzyme activity was highest in C 306, closely followed by PBW 175 and DL 153‐2, and lowest in HD 2428 and HD 2329. It is apparent that water stress induces an increase in hydrogen peroxide content and consequently lipid peroxidation and membrane injury (reduced membrane stability). The degree of oxidative stress and antioxidant activity seems to be closely associated with the tolerance/susceptibility of a genotype to water stress.
Causes of Sterility in Seed Set of Rice under Salinity Stress
Authors: Abdullah Z. , Khan Mushtaq A. , Flowers T. J.
Published: March 2003

The effects of salinity at 50 mM NaCl on floral characteristics, yield components, and biochemical and physiological attributes of the sensitive rice variety IR‐28 were studied under controlled conditions to determine the causes of sterility in seed set under salinity stress. The results showed significant decreases in panicle weight, panicle length, primary branches/panicle, filled seeds/panicle, unfilled seeds/panicle, filled seeds/plant, unfilled seeds/plant, total seeds/panicle, total seed weight/panicle, 1000‐seed weight and total seed weight/plant. The sodium content in different leaves and floral parts increased significantly. In contrast, the potassium content was decreased significantly in leaves and floral parts. A reduction in chlorophyll a and b was also noted in different parts of the leaves. Inhibition of transpiration and photosynthesis was observed in flag leaves at the grain‐filling stage. Soluble carbohydrates in different leaves were reduced significantly in salinized plants but their content in different floral parts was increased, with the exception of primary and secondary branch spikelets. Under salinity stress, total protein concentration in flag, second and third leaves were higher than in control plants. The viability of rice pollen was reduced significantly in salinized plants. It was further observed that starch synthetase activity (α1–4‐glucan glucosyle transferases) in developing rice grains was inhibited very significantly under salinity stress. From these results, it is inferred that sterility and significant reductions in seed set in rice were not merely due to reduction or inhibition of different biochemical constituents and physiological functions, but were mainly due to limitation of soluble carbohydrate translocation in primary and secondary spikelets, accumulation of more sodium and less potassium in all the floral parts, and highly significant inhibition of specific activity of starch synthetase in developing rice grains, thus resulting in failure of seed set.
The Effect of Seeding Rate and Nitrogen Fertilization on Barley Yield and Yield Components in a Cool Maritime Climate
Authors: Spaner D. , Todd A. G. , McKenzie D. B.
Published: March 2003

Soil and climatic conditions in Newfoundland are on the margins of agricultural capability, and almost all feed grain is imported. The overall objective of this work was to develop guidelines for the production of barley in Newfoundland, with the goal of establishing modern cropping recommendations. We conducted a 4‐year study near St. John’s to examine the effect of seeding rate and topdress ammonium nitrate (N) fertilization rate on Chapais six‐row barley (Hordeum vulgare L.) yield components and grain yield. Increasing seeding rate from 200 to 380 seeds m–2 did not alter grain yield in any year. Increasing topdress fertilization from 0 to 60 kg N ha–1 increased spike density m–2 at harvest, resulting in linear increases in grain yield in all years. Highest N rates had greatest lodging in two years. Based on our results, agronomic recommendations for eastern Newfoundland now include barley seeding rates of 250 ± 50 seeds m–2, with topdress applications up to at least 30 kg N ha–1.
Biological Control of Leaf‐Cutting Ants Using Forage Grasses: Nest Characteristics and Fungus Growth
Authors: Michels K. , Cromme N. , Glatzle A. , Schultze‐Kraft R.
Published: March 2003

One of the major pasture pests in the neotropics is the leaf‐cutting ant Acromyrmex landolti, which cuts monocots to nourish a symbiotic fungus as a food source. The objective of the present study was to characterize ant nests and to test the effect of six forage grasses on grass consumption and fungus properties of A. landolti nests. Grasses tested in a 7‐week field experiment during March and April 1997 in the Paraguayan Chaco were Cynodon nlemfuensis, Panicum maximum, Cenchrus ciliaris, Brachiaria brizantha, Digitaria milanjiana and Urochloa mosambicensis. In a bioassay, grass species were evaluated with regard to fungus growth in the laboratory. Results showed that ant nests at that time of year were deeper and had more chambers than often reported in the literature. The two least and most preferred grasses were B. brizantha and C. ciliaris, and C. nlemfuensis and D. milanjiana, respectively. Consumption of the first two grasses was strongly reduced during the second half of the experiment, approaching zero in the last week. The highest fungus weights were found in nests fed with C. nlemfuensis and D. milanjiana. Fungus colony weight and colour proved to be adequate parameters with which to rate the vigour of the fungus; weight was lowest in nests fed with B. brizantha and C. ciliaris. In the bioassays, B. brizantha and D. milanjiana plant saps reduced the fungal growth most and least, respectively. In conclusion, D. milanjiana and C. nlemfuensis can be regarded as highly susceptible to A. landolti, and B. brizantha as resistant; the other grasses cannot be assigned to either group. The bioassay proved to be a quick way of testing the ability of a grass species to inhibit fungal growth.
Stage Sensitivity of Mungbean (Vigna radiata L. Wilczek) to an Elevated Level of Carbon Dioxide
Authors: Das M. , Zaidi P. H. , Pal M. , Sengupta U. K.
Published: March 2003

An experiment was undertaken using open‐top chambers to study the effect of CO2 enrichment on crop growth and to assess the variation related to the time of CO2 exposure. In general, enriched CO2 conditions (600 ± 50 p.p.m.) in the chamber positively affected the growth and development of mungbean (Vigna radiata), a short‐duration (60–65 days) summer pulse crop. However, there was significant variability in the effect of the crop stage/time of CO2 exposure. It was observed that high CO2 exposure at an early growth stage [0–20 days after germination (DAG)] had a larger effect than that at a later growth stage (21–40 DAG). The experiment also provided a means of assessing the short‐ and long‐term effects of elevated CO2 on the carbon exchange rate at both stages of exposure. The study revealed that the sensitivity of plants to high CO2 was more pronounced with respect to net photosynthetic rate. The overall photosynthetic activity gave greater growth and development of plants under high CO2.
Particle Size Distribution (Texture) of Eroded Soil Material
Authors: Basic F. , Kisic I. , Nestroy O. , Mesic M. , Butorac A.
Published: March 2003

The total quantity of erosional drift on a Stagnic Luvisol on which six tillage methods were used was measured over 5 years of investigation. The texture of the tilled soil and the erosional drift for each trial method was recorded in the same plots. The results obtained suggested that erosional drift was generally richer in silt and clay particles. The standard deviations of coarse sand indicated that approximately the same quantity of coarse sand was found in plot soil and in erosional drift for all tillage methods. Sometimes more and sometimes fewer fine sand particles were found in erosional drift than in plot soil. In most cases, more silt particles were found in erosional drift than in plot soil. The standard deviation and coefficient of variation for clay and silt were higher in erosional drift than in plot soil for all methods. The highest content of clay particles was recorded in erosional drift from the no‐tillage treatment in all investigation years. The results suggest that the correct choice of tillage method (no‐tillage and ploughing across the slope) on a Stagnic Luvisol can protect the soil on a slope.
Response of Lentil (Lens culinaris Medik) to Plant Density, Sowing Date, Phosphorus Fertilization and Ethephon Application in the Absence of Moisture Stress
Authors: Turk M. A. , Tawaha A. M. , El‐Shatnawi M. K. J.
Published: March 2003

Lentil (Lenus culinaris Medik) is a major grain legume crop in many developing countries in West Asia, North Africa and many other areas of the world. The effects of sowing date (1 January, 15 January and 2 February), plant density (80, 100 and 120 plants m−2), phosphorus level (0, 17.5, 35.0 and 52.5 kg P ha−1) and ethephon application [(1500 p.p.m. ethephon (2‐chloroethel phosphonic acid) applied 30 days after sowing] were investigated in the semiarid region in the north of Jordan. High yields were obtained for early sowing (1 January), high plant density (120 plants m−2), and high phosphorus application rate (52.5 kg P ha−1). Yield and yield components were not affected by ethephon application 30 days after sowing.
A male bovine linkage map for the ADR granddaughter design
Authors: Thomsen H. , Reinsch N. , Xu N. , Looft C. , Grupe S. , Kühn C. , Brockmann G. A. , Schwerin M. , Leyhe‐Horn B. , Hiendleder S. , Erhardt G. , Medjugorac I. , Russ I. , Förster M. , Brenig B. , Reinhardt F. , Reents R. , Blümel J. , Averdunk G. , Kalm E.
Published: March 2003

The aim of this paper is to present the construction of a male genetic linkage map as a result of the bovine genome mapping project, which is a common effort of the German cattle breeding federation (ADR), four animal breeding institutes, three blood group laboratories and two animal data and breeding value evaluation centres. In total 20 grandsires with 1074 sires were provided from the German cattle population as reference families, 16 of these paternal half‐sib groups are German Holstein families (DH), three are German Simmental (ST) families, and one is a Brown Swiss family (BS). Of 265 markers included in the linkage map, 248 were microsatellite markers, five were bovine blood group systems, eight SSCP markers and four proteins and enzymes. More than 239 000 genotypes resulted from typing the offspring for the respective markers and these were used for the construction of the map. On average 478 informative meioses were provided from each marker of the map. The summarized map length over all chromosomes was 3135.1 cM with an average interval size of 13.34 cM. About 17, 35.7 and 79.1% of the map intervals showed a maximum genetic distance between the adjacent markers of 5, 10 and 20 cM, respectively. The number of loci ranged from two (pseudoautosomal region of the sex chromosome, BTAY) to 15 (BTA23) with an average of 8.8 markers per chromosome. Comparing the length of the chromosomes shows variation from 49.6 cM for BTA26 to 190.5 cM for BTA1 with a mean of 107.7 cM for all autosomes of the genetic linkage map. It was possible to identify chromosomal discrepancies in locus order and map intervals by comparison with other published maps. The map provided sufficient marker density to serve as a useful tool for a scan of segregating quantitative trait loci.
Gene action and heterosis in lifetime traits of Friesian × Sahiwal crosses
Authors: Sharma B. S. , Prabhakaran V. T. , Pirchner F.
Published: March 2003

Gene action and heterosis in seven lifetime traits of Holstein‐Friesian × Sahiwal crosses was studied by fitting genetic additive—dominance and Dickerson, Sheridan models. The additive—dominance model is found adequate for all the traits except ‘average milk yield per day of total productive life’. The heterosis measured from mid‐parent varied from 15% in ‘total life’ to 108% in ‘milk yield from all available lactations’. Heterosis measured from superior parent ranged from 6% in ‘total milk yield of first three lactations’ to 75% in ‘milk yield from all available lactations’. The larger heterosis observed in some of the lifetime traits is attributed as the direct consequence of longer productive life in F1s compared to parental breeds. On the basis of the predicted performance of some of the nonavailable grades like 2/3 exotic, creation of synthetics is mooted.
High frequency of lymphocyte chimerism XX/XY and an analysis of hereditary occurrence of placental anastomoses in Booroola sheep
Authors: Keszka  , Jaszczak  , Klewiec
Published: March 2003

Cytogenetic studies of a closed herd of Booroola Merino sheep were carried out over six consecutive years and covered 167 (90 females and 77 males) sheep originating from 77 heterosexual multiple births. Lymphocyte 54XX/XY chimerism was revealed in 24 litters including 20 (11.98%) ewes and 22 (13.17%) rams, i.e. 25.14% of the karyotyped group of animals and 11.17% of all animals weaned in the herd. Familial and pedigree relations revealed in the study indicate a hereditary tendency to develop placental anastomoses in sheep. Fifteen chimeric litters were sired by six rams. Three rams were carriers of XX/XY chimerism and each sired a chimeric litter. Coefficients of inbreeding ranged from 0.06525 to 0.125 with a mean of 0.094. The pedigree analysis up to the fifth generations showed that two rams were ancestors of all chimeric litters. Based on the analysis of the reproductive performance of dams and sires which produced 32 litters of which three‐quarters were chimeric suggested, that the formation of anastomoses is controlled by a dominant gene.
The influence of selection and epistasis on inbreeding depression estimates
Authors: Curik  , Sölkner  , Stipic
Published: March 2003

Inbreeding depression estimates obtained by regression of the individual performance on the inbreeding were studied by stochastic simulation under various genetic models (solely additive, partial dominance, overdominance and epistasis), and mating strategies (random mating versus selection). In all models, inbreeding depression estimates based on the individual pedigree inbreeding coefficients were compared with estimates based on the true level of autozygosity. For the model with partial dominance and selection, the estimates of inbreeding depression from pedigree information were more negative (lower) than those based on true inbreeding coefficients whereas, in contrast, they were less negative (higher) for the models with overdominance and selection. The difference in the variation of true and pedigree individual inbreeding coefficient indicated that biased estimates might occur even in random mating populations. The estimation of inbreeding depression was further complicated when epistatic effects were present. The sign and the magnitude of the inbreeding effect (depression) estimates might be rather heterogeneous if additive by dominance effects are present because they are strongly dependent on the gene frequency. It was also shown that inbreeding depression is possible in models with negative additive by dominance effects. In models with dominance by dominance inheritance it was difficult to assess the non‐linear relationship between performance and inbreeding, while at the same time, non‐linear estimates based on pedigree information were extremely biased. The results obtained indicate that new or additional methodologies are required if reliable conclusions about consequences of inbreeding depression are needed.
Marker‐based estimates of between and within population kinships for the conservation of genetic diversity
Authors: Eding H. , Meuwissen T. H. E.
Published: March 2003

In this article coefficients of kinship between and within populations are proposed as a tool to assess genetic diversity for conservation of genetic variation. However, pedigree‐based kinships are often not available, especially between populations. A method of estimation of kinship from genetic marker data was applied to simulated data from random breeding populations in order to study the suitability of this method for livestock conservation plans. Average coefficients of kinship between populations can be estimated with low Mean Square Error of Prediction, although a bias will occur from alleles that are alike in state in the founder population. The bias is similar for all populations, so the ranking of populations will not be affected. Possible ways of diminishing this bias are discussed. The estimation of kinships between individuals is imprecise unless the number of marker loci is large (> 200). However, it allows distinction between highly related animals (full sibs, half sibs and equivalent relations) and animals that are not directly related if about 30–50 polymorphic marker genes are used. The marker‐based estimates of kinship coefficients yielded higher correlations than genetic distance measures with pedigree‐based kinships and thus to this measure of genetic diversity, although correlations were high overall. The relation between coefficients of kinship and genetic distances are discussed. Kinship‐based diversity measures conserve the founder population allele frequencies, whereas genetic distances will conserve populations in which allele frequencies are the most different. Marker‐based kinship estimates can be used for the selection of breeds and individuals as contributors to a genetic conservation programme.
Mapping and investigation of the porcine major insulin sensitive glucose transport (SLC2A4/GLUT4) gene as a candidate gene for meat quality and carcass traits
Authors: GRINDFLEK E. , HOLZBAUER R. , PLASTOW G. , ROTHSCHILD M. F.
Published: March 2003

The porcine major insulin sensitive glucose transport gene (known by SLC2A4 and GLUT4) was mapped, by physical and linkage methods, to chromosome 12 in the PiGMaP population. Furthermore, the role of the porcine SLC2A4 was investigated in about 1700 animals from different pig breeds and crosses from the USA and Norway. Ten traits for meat quality and carcass composition were recorded for the U.S. population, while 44 traits for meat quality traits were recorded for the Norwegian population. For the analyses of associations between SLC2A4 gene variants and quantitative traits, one restriction fragment length polymorphism (RFLP) was examined. Relatively weak and inconsistent associations were found in some of the lines investigated between SLC2A4 genotypes and the meat quality traits drip loss, colour, loin marbling and loin depth (p < 0.05). Due to the inconsistencies in the results we conclude that it is likely that the SLC2A4 polymorphism investigated is not associated with meat quality traits in the lines studied.
Studies on energy metabolism in lines of mice selected for different growth parameters
Authors: Klein M. , Schadereit R. , Scholze H. , Renne U.
Published: March 2003

Growth is a very complex physiological process and is controlled by many genes and therefore easy to manipulate by selective breeding. Such manipulation of growth was realized by long‐term selection of laboratory mice for different growth parameters (body weight, total protein amount in the carcass and an index combining body weight and endurance fitness) resulting in a high phenotypic and genetic differentiation compared to the nonselected control (Bünger et al. 1983, 1992, 1994; Renne et al. 1995). After 70 generations the 42‐day body weights increased from 28 g at the start of selection to 58.3 g, 51.9 g and 47.4 g in these lines, respectively (Bünger et al. 1994). At the same time the carcass protein content increased from 2.92 to 5.23 g in the line selected for protein mass without an increase of fat percentage up to the age of 42 days (Renne et al. 1995). In comparison with that, selection for body weight was accompanied by a marked increase of fat percentage up to this age as reported in literature for many long‐term selection experiments. Because of the different chemical composition of the body gain at relatively small differences in growth rate, these selected lines seemed to be suitable models for studying some aspects of energetic efficiency of growth. The results of a former experiment conducted in generations 32–42 suggested a higher efficiency of energy utilization in the line selected for body weight than in the other selected lines (Bünger et al. 1987). The objective of the present study was to characterize the energy metabolism of these different selected lines complementary to the studies on protein metabolism given by Schadereit et al. (1997, 1998).
Evidence of a specific dietary selection for lysine by the piglet
Authors: Kirchgessner M. , Stangl G. I. , Roth F. X.
Published: March 2003

The ability of animals to appropriate sources of food and select among them to obtain a nutritionally adequate diet that is best suited for their physiologic status has been examined in numerous species, but considerable research has addressed self‐selection trials with chicks. Observations on diet preference have led to the assumption that birds have an innate ability to regulate their intake of macro‐ and micronutrients, and that they can do so with a considerable degree of precision (e.g. Holcombe et al. 1975, 1976; Elkin et al. 1985; Harper and Peters 1989; Emmerson et al. 1991; Steinruck et al. 1991a,b; Steinruck and Kirchgessner 1993a,b,c; Shariatmadari and Forbes 1993; Forbes and Shariatmadari 1994, 1996). Experimental evidence also shows that domesticated pigs which are offered a choice between two diets will select a diet containing an adequate amount of protein in preference to one that is deficient in protein, or will select specific proteins among various protein sources (Robinson 1974; Kyriazakis et al. 1990; Kyriazakis and Emmans 1992, 1993; Bradford and Gous 1992; Roberts and Azain 1997). The characteristic amount of a specific protein selected by the animals appeared to be related to the quality of the protein source. This was obvious from a few amino acid selection studies showing that growing‐finishing pigs have the ability to select preferentially amino acid‐adequate diets over amino acid‐deficient diets within a few days (Devilat et al. 1970; Robinson 1975a,b; Davey 1978; Henry 1987, 1993). In contrast, there are also some exceptions to the hypothesis that selection of diet is related to the nutritional quality of the protein fed (Ashley and Anderson 1975). However, some of those studies are not conclusive due to changes in preferences by the animals over time and differences in protein source, palatability and amino acid pattern between the test diets.

Since, an investigation of a self‐selection behaviour by piglets has rarely been studied in detail, the purpose of this research was to determine whether piglets that are given a choice of diets with high or low lysine contents can regulate the intake of each to optimize lysine intake and performance. The objectives of this study were to determine the preference of piglets for diets varying in lysine content and to determine whether the preferences for these diets change with time. This indispensable amino acid was selected for study because it is first limiting in conventional diets for growing pigs.