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Samples of 15 000 seeds from each of nine populations of Agrostis capillaris L. were screened for ability to root in solution cultures containing cadmium, copper, lead, nickel, and zinc at levels which severely inhibited root growth in non-metal-tolerant seed population samples. Differences were found in the extent to which tolerant individuals could be selected from the populations. Only the copper-tolerant cv. Parys and lead-/zinc-tolerant cv. Goginan had relatively high frequencies of individuals tolerant to each metal. Screening one population did not reveal any tolerant individuals. The ability to root in such solutions may reflect the potential populations have to evolve metal-tolerant populations. Populations exhibit considerable variation in this respect and the potential to evolve tolerance is clearly a characteristic of populations, not the species. [ABSTRACT FROM AUTHOR]

Root growth of seedlings of the Agrostis capillaris L. cultvars Parys (copper tolerant), Goginan (lead/zinc tolerant), and Highland (non tolerant) was measured after 14 d growth in solution cultures with increasing concentrations of Cd, Cu, Pb, Ni and Zn. Increasing inhibition of root growth of all three cultivars occurred with increasing concentrations of all five metals, Highland being most affected. In Cu, Parys was least affected; in Pb and Zn Goginan was least affected. Parys and Goginan thus display specific resistance to these metals. They are also similar in having greater root lengths at higher metal concentrations of all five metals than Highland. They thus exhibit non-specific low level tolerance to metals other than those present at toxic levels in the soils from which they were derived. [ABSTRACT FROM AUTHOR]

Sample sub-populations, each of six plants, were chosen for high, mid and low tolerance of copper from each of two naturally-occurring copper tolerant populations and from tolerant individuals selected from a cultivar of Agrostis capillaris L. The naturally-occurring ecotypes came from a closed sward community at Drws y Coed, and from an open community at Parys Mountain, both copper mines in North Wales. Clonal replicates of all plants were introduced into swards of perennial ryegrass cvs. S23 or S24, growing on normal soil at the University of Liverpool Botanic Gardens. S23 plots were cut eight times between June 1977 and July 1978, whilst S24 plots were cut 3 times during the same period. Half the experimental plots received N, P, K, fertilizer; the rest received none. Plants selected from the cultivar (selected) produced most dry matter, and with infrequent defoliation flowered freely in competition with ryegrass. Those taken from Parys Mountain mine spoil produced least dry matter and no inflorescences. Drws y Coed plants were intermediate in dry matter and inflorescence production. These results may reflect differences in population density in the habitats from which the populations were sampled. Sub-populations chosen for high, mid or low copper tolerance within the selected and Drws y Coed populations did not differ significantly in dry matter yield. By contrast under certain circumstances Parys Mountain plants with low tolerance outyielded other more tolerant plants. These results are considered with respect to growth strategies adopted by plants growing on and off copper mine sites. [ABSTRACT FROM AUTHOR]

The number and spatial distribution of perennial ryegrass (Lolium perenne L.) genotypes in 4 pastures were estimated by sampling single tillers from points 5 cm apart on an 11 7times; 11 grid. Three electrophoretic loci were used initially to determine the genotype of each tiller. Three 10-year-old sown swards contained at least 36--43 different genotypes per 0·25 m2 quadrat (10% of the number sown) while a 40-year-old pasture contained only 5 genotypes per 0·25 m2 quadrat. The cut sward had a greater proportion of its area occupied by a few large genotypes than the swards grazed by sheep or cattle. The importance of age, management, and other factors influencing genotypic diversity in swards is discussed. [ABSTRACT FROM AUTHOR]

Dry weight production of seed-derived material of eight genotypes from each of two populations of Poa annua, one from an open and the other from a closed habitat, was compared as pure stands and in mixture with Lolium perenne cv, S23. Comparisons were made in a glasshouse experiment after 13 weeks growth, when uncut, and when cut to a height of 1·5 cm at 5, 7, 9, 11 and 13 weeks from planting. Significant differences were found between genotypes within both populations when cut in pure stands and in mixture with Lolium, and also in uncut stands in mixture with Lolium. When uncut and in pure stands inter-genotypic differences were found only in the open population. Between population differences in within population variation were significant only when the populations were cut and in mixed stands, the open population being mort variable. The closed population was significantly more variable when uncut and in mixed stands than in any other treatment combination, whilst the open population did not van significantly with treatment. The occurrence of genetically-based inter-population differences ,n competitive ability in P. annua is confirmed. [ABSTRACT FROM AUTHOR]

Competition between seed-derived populations of Poa annua from three open and three closed habitats, and Lolium perenne cv. S23 was examined in a glasshouse experiment. Pure stands of P. annua and L. perenne, and 50: 50 mixtures of the two species were compared after 13 weeks growth when uncut, and when cut at 5, 7, 9, 11 and 13 weeks, to a height of 1.5cm. Yields of both the P. annua populations and L. perenne were reduced by both competition and cutting; cutting causing the greatest yield reduction. Mean yield of the three populations from open habitats and of the three populations from closed habitats were regressed on overall mean yields of the four treatment combinations - pure stand uncut, mixed stand uncut, pure stand cut, mixed stand cut. Results indicated that populations from closed habitats performed better in the less favourable conditions imposed by cutting or competition or both these conditions than those from open habitats, whereas this situation was reversed in their absence. Under the cutting and competition treatment the P. annua populations from closed habitats significantly outyielded their Lolium associate. No comparable difference was found for the P. annua populations from open habitats. With competition, uncut P. annua populations from open habitats significantly outyielded Lolium whilst two of the populations from closed habitats, one adjacent to one of the open populations, were significantly outyielded by Lolium. The results suggest that population differentiation in Poa annua has occurred over short distances in response to competition or grazing or mowing and that competitive ability is not a fixed characteristic of a species. [ABSTRACT FROM AUTHOR]

The rooting response of seven populations of Agrostis tenuis Sibth. to a range of copper concentrations in calcium nitrate solution is described. Variation in both index of tolerance and sensitivity of rooting to increased copper levels were found and shown to be phenotypically independent characters. It is suggested that rooting sensitivity to a range of copper concentrations provides a further measure of copper tolerance which is independent of the methods previously employed for assessing tolerance. [ABSTRACT FROM AUTHOR]

Shoot and root growth and plant dry weight were determined for twenty four accessions of pearl millet, Pennisetum americanum (L.) Leeke, after two weeks growth in saline solution culture at EC 20 dS m[sup-1]. The EC was achieved using NaCl + CaCl[sub2] 1 : 1 by weight in solution culture. Although salinity markedly inhibited growth of all accessions, three, 93613, KAT/PM-2 Kitui, and Kitui local produced significantly greater dry matter, and they and 93612 had longer shoots than the other accessions. Accessions WCA 78 and Bulk 7704 were highly sensitive to salinity in all 3 characters measured. There was considerable variation between the 24 accessions, suggesting that selection for increased tolerance to salinity in pearl millet should be possible. This was examined using normal seed of the cultivar A1/3. A first cycle of selection screened 16,000 seeds after 15 days growth in nutrient solution at EC 26 dS m[sup-1]. 106 individuals were selected to form the S[sub1] selection line. Selected seedlings were grown to maturity and polycrossed. In a second cycle of selection, 30,000 S[sub1] polycross progeny were screened as previously, but at EC 30 dS m[sup-1]. A selection intensity of 0.08 % was achieved. The selected plants were again grown to maturity and again polycrossed. Efficiency of the selection procedure was assessed from comparison in sand culture of the performance of the selected line with the unselected A 1/3 line and Kitui local which from the previous assessment of the 24 accessions was rated as relatively salinity tolerant. The selection line was superior to the other two lines at four salinity levels. The results of this study suggest that further improvement in salinity tolerance in pearl millet may expected from further selection and breeding, using the methods described here. [ABSTRACT FROM AUTHOR]

Genetic variation for NaCl tolerance at the vegetative stage was assessed in nutrient solution culture in maize (Zea mays L.). Shoot growth, and plant fresh and dry weight of the two cultivars, Akbar and Sadaf were severely reduced alter three weeks growth in 120, 150, and 180 mol m³ NaCl, There was however considerable variability between seedlings. Ten-thousands seeds of cv. Akbar were therefore screened for shoot growth at 180 mol m ³ NaCl after four weeks growth in sand culture. A selection intensity of 0.42 % was achieved, Eighteen selected plants were polycrossed for estimation of narrow-sense heritability based on female parent-progeny regression. A narrow-sense heritability estimate of 0.54 was obtained. The progeny of the salt-tolerant selection line and selfed progeny plants of the unselected control lines of cvs Akbar and Sadaf were grown for six weeks in 0, 30, 60, 90, 120, 150, and 180 mol m³ NaCI in sand culture. The tolerant line produced significantly greater fresh and dry biomass and had greater shoot length than the unselected cv. Akbar, but the selection line derived from cv. Akbar was equal to the salt tolerant cv. Sadaf in all the growth parameters measured. These data suggest that in maize, improvement in salt tolerance could be obtained through further cycles of selection and breeding. [ABSTRACT FROM AUTHOR]

The genetic basis of salt (NaCI) tolerance at the seedling stage was examined in eight accessions of Sorghum bicolar (L.) Moench which differed in relative NaCI tolerance. The eight accessions were crossed in all possible combinations. The NaCI tolerances of the resulting 56 F[sub1] hybrids and their eight parents were assessed after two weeks growth in solution cultures containing 0, 100, and 150 mM NaCI. Indices of salt tolerance (relative tolerance) were used for analysis using the diallel method. Both additive and dominance effects appeared to be important for the expression of variation under low and high salinity levels, but the effect of genes with dominance properties was more pronounced. Estimates of narrow sense heritabilities for salt tolerance were appreciables, suggesting that rapid improvement in salinity tolerance is possible in this species using high selection pressures in the F[sub2] population. [ABSTRACT FROM AUTHOR]

A macrophage migration inhibitory factor (MIF)-like molecule, Tci-MIF-1, was isolated from Teladorsagia circumcincta and subjected to detailed characterization. A cDNA representing Tci-mif-1 was isolated following its identification in third-stage larvae (L3)-enriched cDNA population. Sequencing of the cDNA indicated a 348-bp open reading frame (ORF) with the closest orthologue being a MIF derived from the human hookworm Ancylostoma ceylanicum. Messenger RNA (mRNA) representing the Tci-MIF-1 transcript was detected in eggs, L3 and adult stages of T. circumcincta. The transcript was also present, but to a lesser extent in fourth-stage larvae (L4). Detection of Tci-MIF-1 protein in T. circumcincta developmental stages reflected the transcript levels identified by reverse transcriptase-PCR. Using immunohistochemistry, the Tci-MIF-1 protein was shown to have a diffuse distribution in L3 tissue, and in L4 and adult stages, the protein was localized to the nematode gut. A recombinant version of Tci-MIF-1 was produced, and enzymic assays indicated that this recombinant protein and a somatic extract of L3 possessed dopachrome tautomerase activity as has been observed previously in other MIF-like molecules. Neither native, purified Tci-MIF nor recombinant Tci-MIF-1 dramatically influenced the in vitro migration of sheep monocytes. [ABSTRACT FROM AUTHOR]

Twenty-five genotypes of early CIMMYT hexaploid wheat (Triticum aestivum L.) were screened for salt tolerance in a glasshouse experiment at 150 mol m-3 NaCl in sand culture. The genotypes Na(20)TPP, Penjamo 62, and Inia 66 exceeded all the lines in grain yield per plant under salt stress, whereas Nainari 60 and Norin 10 were the lowest of all genotypes. However, Jaral 66 and Yaqui 54 were the lowest of all the genotypes in all growth and yield attributes. Considerable variation in accumulation of Na+ and Cl- in different plant parts of 25 genotypes of early CIMMYT wheat under salt stress was observed. The genotype Noreste 66 was the lowest in leaf Na+ and Cl-, and it had highest leaf K/Na ratio and K versus Na selectivity of all the genotypes, but in terms of growth and grain yield, it was moderately tolerant. The other genotype Norin 10 was the highest in leaf Na+ and Cl- of all genotypes, but its leaf K/Na ratio and K versus Na selectivity were considerably low. However, in shoot biomass it was the highest and in grain yield the lowest of all genotypes. In view of phylogenetic lineage of the genotypes, most of the genotypes have evolved from Norin 10, so the trait of high uptake of Na+ and Cl- in most genotypes may have been inherited from Norin 10. The ion exclusion trait in the moderately salt tolerant genotype Noreste 66 was possibly inherited from Yaqui 50 as it was the only among all putative parents which showed low uptake of toxic ions. Overall, owing to the complex nature of the salt tolerance trait being controlled by polygenes, it was not easy to draw relationships between degree of salt tolerance and pattern of uptake of toxic ions and maintenance of leaf K/Na ratios. However, from the phylogenetic lineage of the 25 genotypes it was possible to draw relationships between degree of salt tolerance and mechanism of ion uptake between parents and progeny. [Copyright &y& Elsevier]

(1) This study assessed the relative contributions of plant genotype and two environmental variables to phenotypic variability in demographic traits within adjacent populalions of the perennial grass Holeus lanatus Replicated clones were established in six simulated introductions, or cohorts, in a a reciprocal-transplant experiment (2) In the 'impoved' population, when clonal replicates were transplanted back into their field of origin, survival to reproduction and survival over the two years of the experiment had no significant genetic components of variation In the 'traditional' poputation, in its field of origin, varianon in survival to reproduction had a genetic component of 47%, and survival to the end of the experiment had a generic component of 16%. Because the total phenotypic variances were not different, this suggests that the first populalation had greater phenotype plasticity Variation in number of inflorescences produced by each transplant had a genetic componcnt of 9% in the improved population and 45% in the traditional population. (3) Genotype-environment interaction effects resulted in different relative contributions of genetic and environmental effects when the same traits were measured in the alien field. In all cases variation due to the environment, or phenotypic plasticity, was greater than the genetic variation plus phenotypic carry-over effects. (4) There was no evidence to suggest that clonal transplants had greater vegatative survival in their home fields. For the reproductive character measured (the number of inflorescences per transplant, however, two clones from the traditional populations produced more inflorescenecs in their field of origin; the number of seeds per inflorescence did not vary No evidence for a trade-off between reproduction and survival over the twoyear experiment was found. (5) Repeating the reciprocal-transplant experiment at bye-week intervals showed that time of transplanting significandly... [ABSTRACT FROM AUTHOR]

Our understanding of the deterioration in immune function in old age—immunosenescence—derives principally from studies of modern human populations and laboratory animals. The generality and significance of this process for systems experiencing complex, natural infections and environmental challenges are unknown. Here, we show that late-life declines in an important immune marker of resistance to helminth parasites in wild Soay sheep predict overwinter mortality. We found senescence in circulating antibody levels against a highly prevalent nematode worm, which was associated with reduced adult survival probability, independent of changes in body weight. These findings establish a role for immunosenescence in the ecology and evolution of natural populations. [ABSTRACT FROM AUTHOR]

We aimed to estimate 1) the marginal effect of liver fluke (Fasciola hepatica) infection on productivity of Scottish beef cattle, and 2) the associated greenhouse gas emissions intensity (GHG EI). Data comprised 240,065 abattoir records from NE Scotland from 2014 to 2017, including the presence or absence of lesions typical of liver fluke in the liver at the time of slaughter, from which we inferred liver fluke infection status. The retrospective analysis of abattoir records to estimate marginal effects of an exposure is complicated by the multi-dimensional, clustered nature of the datasets, which result in confounding of potential causal factors with the exposure. Causal inference methods are required to identify and correct for variation in background exposure. We constructed directed acyclic graphs (DAGs) of observed variables, including the potential confounders, breed, sex, breeder, finisher, season of birth and year of birth. We then applied inverse probability weighting (IPW) to adjust for variation among exposure risk and applied a doubly robust generalized linear model (DRGLM) to the weighted observations to estimate the marginal effect of fluke on the growth rate of animals and total days from birth until slaughter. We compared these estimates with the results of linear mixed effects (LME) models with the same variables, treating breeder and producer as random effects. To estimate GHG EI, we applied IPCC tier-2 type GHG calculations to the marginal effects estimated from IPW with DRGLM. The IPW with DRGLM model estimated that animals with active fluke lesions (adult fluke seen on postmortem inspection) gained 17 (95 % CI 12–22) g/d less saleable beef than animals with no lesions and no visible fluke. Animals with active fluke lesions were 11 (95 % CI 6.5–15) d older at slaughter weight than animals with no lesions. Animals with historic lesions in which there was scarring of the liver but in which no adult fluke were seen showed a wide variation in effect estimates, consistent with some misclassification. The effect estimates from LME models suggested slightly lower effects of fluke on growth rate and days to slaughter but with overlapping 95 % confidence intervals. Calculation of the associated GHG emissions suggest the EI of meat from a herd with no fluke is approximately 1.5 % lower than the same herd with fluke. Sustainably controlling liver fluke would have additional production benefits not included in this estimate and could therefore have a much greater impact on GHG EI in practice than demonstrated here. [ABSTRACT FROM AUTHOR]

Summary Spirocerca lupi is a nematode that infects the dog's oesophagus and promotes the formation of an inflammatory fibroblastic nodule that progresses to sarcoma in approximately 25% of cases. Spirocercosis-associated oesophageal sarcoma is an excellent and under-utilized spontaneous model of parasite-associated malignancy. The inflammatory infiltrate of paraffin-embedded, non-neoplastic oesophageal nodules ( n = 46), neoplastic nodules ( n = 25) and normal oesophagus ( n = 14) was examined by immunohistochemistry using MAC387 (myeloid cells), CD3 (T cells), Pax5 (B cells) and FoxP3 (T regulatory cells) antibodies. Myeloid cells predominated in 70% of nodules, in pockets around the worms' migratory tracts and in necro-ulcerative areas in neoplastic cases. T cells predominated in 23% of cases with a focal or diffuse distribution, in the nodule periphery. No significant differences were observed between neoplastic and non-neoplastic stages. FoxP3+ cells were observed in low numbers, not significantly different from the controls. The inflammation in spirocercosis is characterized by pockets of pus surrounded by organized lymphoid foci. There was no evidence of a local accumulation of FoxP3+ cells, unlike many previous studies that have reported an increase in FoxP3+ T cells in both malignancies and parasite infections. The triggering factor(s) driving the malignant transformation of the spirocercosis-associated chronic inflammatory nodule warrants further investigation. [ABSTRACT FROM AUTHOR]

Sheep scab is caused by the noninvasive mite, Psoroptes ovis , which initiates a profound pro-inflammatory skin response leading to lesion development. To investigate these early events between the skin and the parasite, primary ovine epidermal keratinocyte cultures were generated and challenged with mite derived antigens. The kinetics of the mRNA response of these cells were monitored by microarray. The results indicated that the cells responded within 1 h of challenge, with a significant increase in the pro-inflammatory cytokine IL-8. This result was confirmed by real-time RT-PCR, and showed that IL-8 up-regulation was maximal at 1 h but declined to pre-stimulation levels at 24 and 48 h. The IL-8 mRNA response to mite wash antigens containing secretory and/or excretory proteins was also investigated and compared to the response to whole mite antigen. These studies revealed that the mite wash antigen, at a challenge dose of 10 µg/mL, was markedly more potent and induced significantly higher levels of IL-8 mRNA than the same concentration of whole mite antigen. These results are discussed in relation to mite establishment and survival on the ovine host. [ABSTRACT FROM AUTHOR]