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Genotypic Variation (genotypic + variation)
Selected AbstractsGenotypic variation in patterns of root distribution, nitrate interception and response to moisture stress of a perennial ryegrass (Lolium perenne L.) mapping populationGRASS & FORAGE SCIENCE, Issue 3 2007J. R. Crush Abstract Genotypic variation in patterns of root distribution, nitrate interception and response to moisture stress were assessed in both parents and 198 progeny of a perennial ryegrass (Lolium perenne L.) full-sibling mapping population. This was carried out in metre-deep tubes of sand culture in a glasshouse experiment. The proportion of root dry matter (DM) weight in the top 10 cm of sand ranged from 0·33 to 0·75 and values of log10(1 , K), where K is the constant for an exponential model relating root DM weight and root depth, also showed wide variation among genotypes. The proportion of a pulse of 15N recovered in whole plants ranged from 0·124 to 0·431. There was a positive linear correlation between the proportion of 15N recovered and plant total DM weight, but no relationship between nitrate interception and patterns of distribution of DM weight of roots. Some genotypes responded to moisture stress by increasing root growth, and in others root growth was inhibited. It is concluded that this below-ground variability in root variables may be an evolutionary adaptation by plant populations to survive heterogeneity in soil biotic and edaphic factors. [source] Genetic and Pathogenic Variation Among Tobacco Black Shank Strains of Phytophthora parasitica var. nicotianae from the Main Tobacco Growing in ChinaJOURNAL OF PHYTOPATHOLOGY, Issue 5 2003X. G. Zhang Abstract Pathogenic and genetic variability among seven populations of Phytophthora parasitica var. nicotianae from individual tobacco fields (Yunnan, Shandong, Henan, Heilongjiang, Shanxi, Fujian and Sichuan provinces) were investigated using pathogenicity and randomly amplified polymorphic DNA (RAPD) analyses; 63 strains were isolated from different fields of seven tobacco growing regions, using tobacco cv. Hongda as a baiting host. Pathogenic variability was evaluated in greenhouse studies using five tobacco cultivars that have different levels of resistance to tobacco black shank; 75 and 73% of the strains were pathogenic on M3 and M4, 29 and 33% on M1 and M2, and 94% were pathogenic on M5, respectively. Disease severity incited by different strains varied significantly on individual tobacco cultivars. The percentage of strains pathogenic on different cultivars varied among locations. Genotypic variation among 63 strains was evaluated by RAPD analysis. Ten primers detected 89 polymorphic bands. Cluster and principal coordinates analysed cluster groups. the minor group contained 26 strains, and major group contained 37 strains. Estimates of genetic diversity based on RAPD analysis ranged from 0.24 to 0.34 within populations to 0.36 among all strains from all populations. Phytophthora parasitica var. nicotianae populations were genotypically and phenotypically variable, but no distinct genotypic differences were identified among populations from the seven locations. [source] Genotypic variation of potato for phosphorus efficiency and quantification of phosphorus uptake with respect to root characteristicsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2009Tesfaye Balemi Abstract Potato (Solanum tuberosum L.), an important food crop, generally requires a high amount of phosphate fertilizer for optimum growth and yield. One option to reduce the need of fertilizer is the use of P-efficient genotypes. Two efficient and two inefficient genotypes were investigated for P-efficiency mechanisms. The contribution of root traits to P uptake was quantified using a mechanistic simulation model. For all genotypes, high P supply increased the relative growth rate of shoot, shoot P concentration, and P-uptake rate of roots but decreased root-to-shoot ratio, root-hair length, and P-utilization efficiency. Genotypes CGN 17903 and CIP 384321.3 were clearly superior to genotypes CGN 22367 and CGN 18233 in terms of shoot,dry matter yield and relative shoot-growth rate at low P supply, and therefore can be considered as P-efficient. Phosphorus efficiency of genotype CGN 17903 was related to higher P-utilization efficiency and that of CIP 384321.3 to both higher P-uptake efficiency in terms of root-to-shoot ratio and intermediate P-utilization efficiency. Phosphorus-efficient genotypes exhibited longer root hairs compared to inefficient genotypes at both P levels. However, this did not significantly affect the uptake rate and the extension of the depletion zone around roots. The P inefficiency of CGN 18233 was related to low P-utilization efficiency and that of CGN 22367 to a combination of low P uptake and intermediate P-utilization efficiency. Simulation of P uptake revealed that no other P-mobilization mechanism was involved since predicted uptake approximated observed uptake indicating that the processes involved in P transport and morphological root characterstics affecting P uptake are well described. [source] Temperature checks the Red Queen?ECOLOGY LETTERS, Issue 1 2003Resistance, virulence in a fluctuating environment Abstract Numerous studies have revealed genetic variation in resistance and susceptibility in host,parasite interactions and therefore the potential for frequency-dependent selection (Red Queen dynamics). Few studies, if any, have considered the abiotic environment as a mediating factor in these interactions. Using the pea aphid, Acyrthosiphon pisum, and its fungal pathogen, Erynia neoaphidis, as a model host,parasite system, we demonstrate how temperature can mediate the expression of genotypic variation for susceptibility and virulence. Whilst previous studies have revealed among-clone variation in aphid resistance to this pathogen, we show that resistance rankings derived from assessments at one temperature, are not conserved across differing temperature regimes. We suggest that variation in environmental temperature, through its nonlinear impact on parasite virulence and host defence, may contribute to the general lack of evidence for frequency-dependent selection in field systems. [source] Patterns of phenotypic and genetic variability show hidden diversity in Scottish Arctic charrECOLOGY OF FRESHWATER FISH, Issue 1 2007C. E. Adams Abstract,,, This study examined the degree and pattern of variability in trophic morphology in Arctic charr (Salvelinus alpinus L.) at three spatial scales: across 22 populations from Scotland and between and within two adjacent catchments (Laxford and Shin) in northern Scotland. In addition, the variability at six microsatellite loci between and within the Laxford and Shin systems was determined. Habitat use by charr differed significantly between populations. The pattern of variability in trophic morphology, known to influence foraging ability in charr, showed a very high degree of between-population variation with at least 52% of population pairs showing significant differences in head shape. Trophic morphology and genetic variation was also high over small geographical scales; variation being as high between charr from lakes within the same catchment, as between adjacent catchments. The pattern of both phenotypic and genotypic variation suggests a mosaic of variation across populations with geographically close populations often as distinct from each other as populations with much greater separation. Very low levels of effective migrants between populations, even within the same catchment, suggest that this variation is being maintained by very low straying rates between phenotypically and genetically distinct populations, even when there is no apparent barrier to movement. We conclude that the genetic and phenotypic integrity of charr populations across Scotland is high and that this adaptive radiation constitutes a ,hidden' element of diversity in northern freshwater systems. Two consequences of this are that the population (rather than the species) makes a more rational unit for the consideration of conservation strategies and that the habitat requirements and therefore management needs may differ significantly between populations. [source] Willow genotype, but not drought treatment, affects foliar phenolic concentrations and leaf-beetle resistanceENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2004Carolyn Glynn Abstract In a greenhouse experiment we examined the effect of willow genotype and irrigation regime (moderate drought and well-watered) on plant growth parameters, foliar nitrogen, and phenolic concentrations, as well as on the preference and performance of the blue leaf beetle, Phratora vulgatissima (L.) (Coleoptera: Chrysomelidae). The 10 vegetatively propagated willow genotypes in the experiments were F2 full-sibling hybrids, originated from a cross between Salix viminalis (L.) (Salicaceae) (high in condensed tannins) and Salix dasyclados (L.) (Salicaceae) (rich in phenolic glycosides). Insect bioassays were conducted on detached leaves in Petri dishes as well as with free-living insects on intact potted plants. The 10-week long irrigation treatments caused statistically significant phenotypic differences in the potted willow saplings. Total biomass was somewhat higher in the well-watered treatment. The root to total biomass ratio was higher in the drought-treatment plants. There was significant genotypic variation in foliar nitrogen concentrations, and they were higher in the drought-treatment plants. There was also a strong genotypic variation in each of the phenolic substances analyzed. Condensed tannins, which accounted for the greatest proportion of total phenolic mass, were higher in the well-watered treatment. There was, however, no difference in levels of the other phenolics (salicylates, cinnamic acid, flavonoids, and chlorogenic acid) between irrigation treatments. The sum of these phenolics was higher in the well-watered treatment. There was a strong variation in P. vulgatissima larval development on different willow genotypes, and larval performance was negatively correlated with levels of salicylates and cinnamic acid. There was, however, no effect of irrigation treatment on larval performance. Phratora vulgatissima preferred to feed on well-watered plants, and we found a preference for oviposition there, but neither feeding nor oviposition site preference was affected by willow genotype. Adult feeding and oviposition preferences were not correlated with larval performance. [source] Mortality in seedling populations of Silver Birch: genotypic variation and herbivore effectsFUNCTIONAL ECOLOGY, Issue 5 2003K. Prittinen Summary 1Variation among mature plants reflects mortality that has occurred during the seedling phase. Our earlier studies have shown variation in resistance to insect and vole herbivory among Silver Birch genotypes that represent variation in a naturally regenerated birch stand. The aim of this study was to examine whether seedling mortality varied among these genotypes, and whether insect and field vole herbivory affected mortality. The 20 genotypes studied competed with each other in dense stands, which were randomly assigned to insect and vole exposure and fertilization treatments. 2Insect herbivory and fertilization increased mortality significantly (by 98 and 68%, respectively). The fertilization effect was probably due to accelerated self-thinning among fast-growing seedlings. Although vole browsing removed considerable biomass, it did not affect seedling mortality. 3Mortality was context-dependent. The genotypes differed both in their overall mortality and in their response to insect herbivory. However, the effect of insects on a genotype depended more on its success in competition than on its resistance: even small amounts of feeding were detrimental to short, shaded seedlings, while taller seedlings in the canopy were affected less, although they were eaten more. 4It is concluded that moderate levels of insect herbivory can increase seedling mortality considerably. Furthermore, herbivory can change the genetic structure of birch populations through selective mortality, which in dense stands is dependent on competitive traits. [source] Effect of drought on the growth of Lolium perenne genotypes with and without fungal endophytesFUNCTIONAL ECOLOGY, Issue 6 2000G. P. Cheplick Abstract 1Grass leaves are often inhabited by fungal endophytes that can enhance host growth. In some forage species, endophytes improve host resistance to, and recovery from, drought. 2Our objective was to determine if the growth of genotypes of Lolium perenne L. was improved by endophytes during recovery from drought. 3Thirteen infected genotypes were cloned into ramets. Half were treated with a systemic fungicide to eliminate the endophyte (E,); half were untreated and retained high endophyte levels (E+). In a glasshouse, half of all E, and E+ ramets were watered regularly, whilst half were exposed to a 2 week drought on two occasions, each followed by a 3 week recovery period. 4After the first drought and recovery period, endophytes significantly reduced tiller production in the drought-stressed group. 5After the second drought and recovery period, effects of drought on live leaf area and dry mass were highly dependent on host genotype, but not endophytes. The mean tiller mass of E+ ramets after drought was significantly less than that of watered E+ ramets, but this was not true in E, ramets. For six genotypes there was greater mass allocation to storage in the tiller bases of E, ramets after drought. 6This perennial ryegrass population showed marked genotypic variation in the ability to recover from drought stress, but endophytes played little or no role in this ability. For some host genotypes there may be a metabolic cost of harbouring endophytes during environmentally stressful conditions. [source] The effect of sward structure as influenced by ryegrass genotype on bite dimensions and short-term intake rate by dairy cowsGRASS & FORAGE SCIENCE, Issue 1 2003P. D. Barrett Abstract The effects of genotypic variation in ryegrasses on sward structure, bite dimensions and intake rate by dairy cows were investigated. Two experiments were conducted. In Experiment 1, swards were in a vegetative state whereas, in Experiment 2, they were partly reproductive and were taller with higher herbage mass but lower leaf proportion than in Experiment 1. Applicability of relationships between sward structure and bite characteristics, previously established from artificial or hand-constructed swards, to field conditions were tested. Additional short-term intake rates and/or sward structural characteristics were considered as indicators of potential intake for use in protocols for the evaluation of grass varieties. Four cultivars were studied: AberElan, Twins (diploid and tetraploid perennial ryegrasses respectively), Polly, a hybrid ryegrass (perennial × Italian ryegrass) and Multimo (Italian ryegrass), each established in 200-m2 plots in four replicated blocks. Herbage intake rate was determined by short-term liveweight change (taking account of insensible weight loss) using 16 dairy cows allocated to four balanced groups with each plot grazed by one group for a 1-h assessment period. One block was grazed per day, over a 4-d experimental period, with each group grazing each variety in a complete crossover design. Sward characteristics and bite rate were also measured in both experiments. Bite dimensions were subsequently estimated, with bite depth being determined as a function of extended tiller height (ETH) in both experiments. Within both experiments, bite mass and intake rate did not differ significantly between swards of different cultivars despite swards containing Multimo generally having a higher ETH and water-soluble carbohydrate concentration and lower green leaf mass, sward bulk density and neutral-detergent fibre concentration than the other swards. However, bite depth was significantly higher (P < 0·01) in swards containing Multimo swards than in the others and, in Experiment 1, bite depth, as a proportion of ETH, was higher in swards containing Multimo and lower in those containing Twins than in the other two cultivars, whereas there was no difference in Experiment 2. Taking both experiments together, the mean bite depth was 0·5 of ETH with sward bulk density accounting for almost half the variance in the relationship between bite depth and ETH. The bulk density of the bite (bite mass per unit bite volume), measured in Experiment 2, followed a similar pattern to sward bulk density, increasing in the order Multimo, Polly, AberElan and Twins. It is concluded that the relationships between sward characteristics and bite dimensions, derived from artificial swards, are applicable to field swards, although the range in natural ryegrass sward characteristics is usually not as wide as in experiments using artificial swards. Lack of precision in the measurement of short-term intake and in sward-based measurements is likely to preclude their use in the evaluation of grass varieties. [source] Compound KIR - HLA genotype analyses in the Iranian population by a novel PCR,SSP assayINTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 3 2010N. Tajik Summary Natural killer (NK) cells eliminate infected and transformed cells while still are self-tolerant. Interactions of the independently segregating Killer cell immunoglobulin-like receptors (KIR) and human leucocyte antigens (HLA) loci play a critical role in NK cell regulation. Different compound KIR-HLA genotypes can impart different thresholds of activation to the NK-cell repertoire and such genotypic variation has been found to confer altered risk in a number of human diseases including viral infections, autoimmune disorders, reproduction abnormalities and cancers. In this study, we presented a novel combined KIR-HLA polymerase chain reaction,sequence-specific primers genotyping assay for simultaneous determination of KIR genes and their three major HLA class I ligand groups (C1, C2, and Bw4). Moreover, known inhibitory and activating KIR + HLA (iKIR + HLA: 2DL2/3 + C1, 2DL1 + C2, 3DL1 + Bw4; and aKIR + HLA: 2DS2 + C1, 2DS1 + C2, 3DS1 + Bw4) combinations as well as co-inheritance of aKIR genes and iKIR + HLA pairs were analysed in a total of 200 unrelated healthy Iranian individuals. All tested subjects had at least one of the three iKIR + HLA pairs and the frequencies of various inhibitory combinations in the study group were: 31.5%, three iKIR + HLA pairs, 53.5%, two iKIR + HLA pairs, and 15%, 0ne iKIR + HLA pair. Furthermore, we revealed that majority of Iranians (69%) carry compound genotypes with greater number of inhibitory pairings than activating combinations (iKIR + HLA > aKIR + HLA). Conversely, iKIR + HLA < aKIR (45%) was dominant genotype in the study group. We conclude that selective evolutionary pressure has propensity to maintain KIR-HLA genotypes with more inhibitory combinations to guarantee self-tolerance. In contrast, existence of activating KIR genes without normal endogenous ligands, potentially arms the NK population for competent immunosurveillance and stronger defense against infections. [source] Relationship of Carbon Isotope Discrimination to Water Use Efficiency and Productivity of Barley Under Field and Greenhouse ConditionsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2007A. O. Anyia Abstract This study was conducted to evaluate the application of carbon isotope discrimination (CID) as a selection criterion for improving water use efficiency (WUE) and productivity of barley (Hordeum vulgare L.) under field and drought-stress conditions in a greenhouse. A total of 54 genotypes were screened for variability in CID under field conditions, while 23 genotypes were evaluated under water-deficit conditions in the greenhouse. A survey of leaf CID of 54 genotypes at two field locations showed more than 2.14, difference between extreme genotypes. Significant (P , 0.05) genotypic variation was found in WUE and CID that had a negative strong correlation. There was a negative correlation between leaf CID and aerial biomass in the greenhouse and among six-row genotypes in the field. Correlations between leaf CID across field locations and across irrigation regimes in the greenhouse were significant (experiment 1, r = 0.79 and 0.94 for six- and two-row genotypes), suggesting stability of the CID trait across different environments. Overall, these results indicate the potential of leaf CID as a reliable method for selecting for high WUE and productivity in barley breeding programmes in the Canadian prairies. Further work is currently underway to determine heritability/genetics of leaf CID and application of molecular marker-assisted selection for the traits in barley breeding programmes. [source] Alternative measures of response to Pseudomonas aeruginosa infection in Drosophila melanogasterJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2007V. CORBY-HARRIS Abstract Studies of invertebrate immune defence often measure genetic variation either for the fitness cost of infection or for the ability of the host to clear the parasite. These studies assume that variation in measures of resistance is related to variation in fitness costs of infection. To test this assumption, we infected strains of the fruit fly, Drosophila melanogaster, with a pathogenic bacterium. We then measured the correlation between host bacterial load and the ability to survive infection. Despite the presence of genotypic variation for both traits, bacterial load and survival post-infection were not correlated. Our results support previous arguments that individual measures of immune function and the host's ability to survive infection may be decoupled. In light of these results, we suggest that the difference between tolerance and resistance to infection, a distinction commonly found in the plant literature, may also be of value in studies of invertebrate immunity. [source] Screening for Drought Resistance of Rice Recombinant Inbred Populations in the FieldJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 10 2007Gui-Hua Zou Abstract In a 2-year experiment, 187 genotypes were grown under well-watered and drought stress conditions, imposed at panicle initiation stage. The relationship of genotypic variation in yield under drought conditions to potential yield, heading date and flowering delay, reduction in plant height, and to a drought response index (DRI) was detected. Grain yield under drought stress conditions was associated with yield under well-watered conditions (r = 0.47**, and r = 0.61** during 2 years of tests). The delay of heading date ranged from ,1 (no delay) to 24 days, and was negatively associated with grain yield (r = ,0.40*), spikelet fertility percentage (r = ,0.40**), harvest index (r = ,0.58**), but positively associated with yield reduction percentage (r = 0.60**). The reduction in plant height was negatively associated with grain yield (r = ,0.24**, and r = ,0.29**), spikelet fertility percentage (r = ,0.23**, and r = ,0.21*), harvest index (r = ,0.37**, and r = ,0.54**), and positively associated with yield reduction percentage (r = 0.58**, and r = 0.58**) in 2003 and 2004, respectively. The DRI of genotypes was strongly associated with grain yield (r = 0.87**, and r = 0.77**), fertility percentage (r = 0.66** and r = 0.54**), harvest index (r = 0.67** and r = 0.61**), and negatively associated with grain reduction percentage (r = ,0.70**, and r = ,0.73**) under drought stress. The results indicate that genotypes with drought resistance can be identified by measuring yield potential, delay in flowering, reduction in plant height, or DRI under test environments of well-watered and drought stress. [source] Assessing the Suitability of Various Physiological Traits to Screen Wheat Genotypes for Salt ToleranceJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2007Salah E. El-Hendawy Abstract Success of improving the salt tolerance of genotypes requires effective and reliable screening traits in breeding programs. The objective was to assess the suitability of various physiological traits to screen wheat genotypes for salt tolerance. Thirteen wheat genotypes from Egypt, Germany, Australia and India were grown in soil with two salinity levels (control and 150 mmol/L NaCl) in a greenhouse. The physiological traits (ion contents in leaves and stems, i.e. Na+, Cl,, K+, Ca2+), the ratios of K+/Na+ and Ca+/Na+ in the leaves and stems, net photosynthesis rate, stomatal conductance, transpiration rate, chlorophyll content (SPAD value), and leaf water relations, were measured at different growth stages. The physiological traits except for Na+ and Cl, in stems and the leaf transpiration rate at 150 mmol/L NaCl showed a significant genotypic variation, indicating that the traits that have a significant genotypic variation may be possibly used as screening criteria. According to the analysis of linear regression of the scores of the physiological traits against those of grain yield, however, the physiological traits of Ca2+ and Ca2+/Na+ at 45 d and final harvest with the greatest genotypic variation were ranked at the top. From a practical and economic point of view, SPAD value should be considered to be used as screening criteria and/or there is a need to develop a quick and practical approach to determine Ca2+ in plant tissues. [source] Variation in Resistance of Camelina (Camelina sativa [L.] Crtz.) to Downy Mildew (Peronospora camelinae Gäum.)JOURNAL OF PHYTOPATHOLOGY, Issue 3-4 2001Vollmann Camelina (Camelina sativa) is a potential oilseed crop for both food and non-food utilization cultivated on a limited acreage in Europe and North America. An important low-input feature of camelina is its high level of resistance against plant diseases, which may partly be due to the production of antimicrobially efficient phytoalexins. In Central European countries such as Austria, downy mildew (Peronospora camelinae) is the only disease of camelina which has been found repeatedly, whereas other diseases and pests have been observed only occasionally. Therefore, the genotypic variation of downy mildew incidence was evaluated in two camelina field experiments carried out within a breeding programme. In both experiments, totally resistant breeding lines were identified and a continuous pattern of variation in disease incidence was observed, suggesting a horizontal type of resistance. In bi-parental populations, disease incidence of progeny appeared to be associated with disease scores of the parent genotypes, and transgressive segregation in disease incidence was also found. In 1998, the rate of downy mildew in camelina was lower than in 1999; in the latter growing season, grain yield was significantly affected by the disease, whereas other agronomic characters remained unaffected. Variation der Resistenz von Leindotter (Camelina sativa[L.] Crtz.) gegen Falschen Mehltau (Peronospora camelinae Gäum.) Leindotter (Camelina sativa) ist eine Ölpflanze, die zur Nahrungsmittelherstellung und für andere Zwecke genutzt werden kann und in Europa und Nordamerika auf relativ kleiner Fläche angebaut wird. Ein wichtiges Low-Input-Merkmal des Leindotters ist seine hohe Krankheitsresistenz, die vermutlich teilweise auf die Bildung antimikrobiell wirksamer Phytoalexine zurückgeht. In Österreich und anderen Ländern Mitteleuropas ist Falscher Mehltau (Peronospora camelinae) die einzige regelmäßig anzutreffende Krankheit des Leindotters, andere Krankheiten und Schädlinge werden nur gelegentlich beobachtet. Daher wurde die genotypische Variation der Inzidenz des Falschen Mehltaus im Rahmen eines Leindotter-Züchtungsprogramms in zwei Feldversuchen geprüft. In beiden Versuchen wurden vollständig resistente Zuchtlinien identifiziert, und ein kontinuierliches Variationsmuster der Krankheitsresistenz wurde beobachtet, was auf horizontale Resistenz schließen läßt. In biparentalen Populationen war die Befallshänfigkeit bei den Nachkommen offenbar mit den Boniturwerten der elterlichen Genotypen assoziiert, und bei der Befallshänfigkeit wurde auch eine transgressive Aufspaltung beobachtet. 1998 war der Befall des Leindotters mit Falschem Mehltau geringer als 1999; im letztgenannten Jahr war der Kornertrag infolge der Krankheit deutlich verringert, während andere agronomische Merkmale unbeeinflußt blieben. [source] Patterns, sources and ecological implications of clonal diversity in apomictic Ranunculus carpaticola (Ranunculus auricomus complex, Ranunculaceae)MOLECULAR ECOLOGY, Issue 4 2006O. PAUN Abstract Sources and implications of genetic diversity in agamic complexes are still under debate. Population studies (amplified fragment length polymorphisms, microsatellites) and karyological methods (Feulgen DNA image densitometry and flow cytometry) were employed for characterization of genetic diversity and ploidy levels of 10 populations of Ranunculus carpaticola in central Slovakia. Whereas two diploid populations showed high levels of genetic diversity, as expected for sexual reproduction, eight populations are hexaploid and harbour lower degrees of genotypic variation, but maintain high levels of heterozygosity at many loci, as is typical for apomicts. Polyploid populations consist either of a single AFLP genotype or of one dominant and a few deviating genotypes. genotype/genodive and character incompatibility analyses suggest that genotypic variation within apomictic populations is caused by mutations, but in one population probably also by recombination. This local facultative sexuality may have a great impact on regional genotypic diversity. Two microsatellite loci discriminated genotypes separated by the accumulation of few mutations (,clone mates') within each AFLP clone. Genetic diversity is partitioned mainly among apomictic populations and is not geographically structured, which may be due to facultative sexuality and/or multiple colonizations of sites by different clones. Habitat differentiation and a tendency to inhabit artificial meadows is more pronounced in apomictic than in sexual populations. We hypothesize that maintenance of genetic diversity and superior colonizing abilities of apomicts in temporally and spatially heterogeneous environments are important for their distributional success. [source] Comparison of inflammatory changes caused by Porphyromonas gingivalis with distinct fimA genotypes in a mouse abscess modelMOLECULAR ORAL MICROBIOLOGY, Issue 3 2004K. Nakano The fimA gene of Porphyromonas gingivalis, encoding fimbrillin (a subunit protein of fimbriae) has been classified into six genotypes (types I,V and Ib). The genotypic variation was previously suggested to be related to the severity of adult periodontitis in the general population. In this study, we compared inflammatory changes caused by bacterial infection to study pathogenic heterogeneity among the different fimA strains in a mouse abscess model. Bacterial suspensions of 13 P. gingivalis strains representing the six fimA types were subcutaneously injected into female BALB/c mice, and serum sialic acid concentrations were assayed as a quantitative host inflammatory parameter. Type II fimA organisms caused the most significant induction of serum sialic acid, as well as other infectious symptoms, followed by types Ib, IV and V. In contrast, types I and III caused weak inflammatory changes. In addition, fimA mutants of type II strains clearly lost their infectious ability. These findings suggest that fimA genotypic variation affects expression of P. gingivalis virulence. [source] Early life events and their consequences for later disease: A life history and evolutionary perspectiveAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2007Peter D. Gluckman Biomedical science has little considered the relevance of life history theory and evolutionary and ecological developmental biology to clinical medicine. However, the observations that early life influences can alter later disease risk,the "developmental origins of health and disease" (DOHaD) paradigm,have led to a recognition that these perspectives can inform our understanding of human biology. We propose that the DOHaD phenomenon can be considered as a subset of the broader processes of developmental plasticity by which organisms adapt to their environment during their life course. Such adaptive processes allow genotypic variation to be preserved through transient environmental changes. Cues for plasticity operate particularly during early development; they may affect a single organ or system, but generally they induce integrated adjustments in the mature phenotype, a process underpinned by epigenetic mechanisms and influenced by prediction of the mature environment. In mammals, an adverse intrauterine environment results in an integrated suite of responses, suggesting the involvement of a few key regulatory genes, that resets the developmental trajectory in expectation of poor postnatal conditions. Mismatch between the anticipated and the actual mature environment exposes the organism to risk of adverse consequences,the greater the mismatch, the greater the risk. For humans, prediction is inaccurate for many individuals because of changes in the postnatal environment toward energy-dense nutrition and low energy expenditure, contributing to the epidemic of chronic noncommunicable disease. This view of human disease from the perspectives of life history biology and evolutionary theory offers new approaches to prevention, diagnosis and intervention. Am. J. Hum. Biol. 19:1,19, 2007. © 2006 Wiley-Liss, Inc. © 2006 Wiley-Liss, Inc. [source] A novel transcriptomic approach to identify candidate genes for grain quality traits in wheatPLANT BIOTECHNOLOGY JOURNAL, Issue 5 2009Yongfang Wan Summary A novel methodology is described in which transcriptomics is combined with the measurement of bread-making quality and other agronomic traits for wheat genotypes grown in different environments (wet and cool or hot and dry conditions) to identify transcripts associated with these traits. Seven doubled haploid lines from the Spark × Rialto mapping population were selected to be matched for development and known alleles affecting quality. These were grown in polytunnels with different environments applied 14 days post-anthesis, and the whole experiment was repeated over 2 years. Transcriptomics using the wheat Affymetrix chip was carried out on whole caryopsis samples at two stages during grain filling. Transcript abundance was correlated with the traits for approximately 400 transcripts. About 30 of these were selected as being of most interest, and markers were derived from them and mapped using the population. Expression was identified as being under cis control for 11 of these and under trans control for 18. These transcripts are candidates for involvement in the biological processes which underlie genotypic variation in these traits. [source] Effect of the Rht-D1 dwarfing locus on Fusarium head blight rating in three segregating populations of winter wheatPLANT BREEDING, Issue 4 2008H.-H. Voss Abstract Fusarium head blight (FHB) is one of the major fungal diseases in wheat throughout the world. To control FHB severity, breeding genetically resistant varieties is thought to be the most promising strategy. In wheat breeding programmes, short cultivars predominantly carrying the Norin 10 derived semi-dwarfing allele Rht-D1b (Rht2) are preferred worldwide because of higher achievable grain yields and lower risk of lodging. This study was conducted to determine the influence of different alleles at the Rht-D1 locus on FHB reaction. Three winter wheat populations were produced by crossing rather susceptible varieties ,Biscay', ,Pirat' and ,Rubens' carrying mutant-type allele Rht-D1b with the more resistant varieties ,Apache', ,Romanus' and ,History' containing the Rht-D1a wild-type allele (rht2). The 190, 216 and 103 progeny of the F4 -derived populations were assayed for the presence of Rht-D1a or Rht-D1b, plant height, and mean FHB rating after spray inoculation at flowering time with a highly aggressive isolate of Fusarium culmorum. Comparably, high mean FHB severities ranging from 28% to 49% for all population × environment combinations were achieved, with significant genotypic variation for FHB rating and plant height within all populations. Both traits were negatively correlated with r ranging from ,0.48 to ,0.61 in the complete populations. However, within the subpopulations homozygous for one or other height allele these correlations decreased considerably. The Rht-D1b semi-dwarfing allele resulted in 7,18% shorter plants, depending on the population, but a considerably increased FHB reaction of 22,53%. Nevertheless, significant genotypic variance for FHB resistance remained in all tested Rht-D1b subpopulations indicating that selection for moderately FHB resistant genotypes within agronomically beneficial Rht-D1b genotypes is still feasible. [source] Quantitative-genetic analysis of leaf-rust resistance in seedling and adult-plant stages of inbred lines and their testcrosses in winter ryePLANT BREEDING, Issue 6 2002T. Miedaner Abstract Leaf rust is the most frequent leaf disease of winter rye in Germany. All widely grown population and hybrid varieties are susceptible. This study was undertaken to estimate quantitative-genetic parameters of leaf-rust resistance in self-fertile breeding materials with introgressed foreign leaf-rust resistances and to analyze the relative importance of seedling and adult-plant resistance. Forty-four inbred lines and their corresponding testcrosses with a highly susceptible tester line were grown in a field in four different environments (location-year combinations) with artificial inoculation. Plots were separated by a nonhost to promote autoinfections and minimize interplot interference. Leaf-rust severity was rated on three leaf insertions at three dates. The testcrosses showed a considerably higher disease severity than the lines. High correlations (r , 0.9, P = 0.01) existed among the leaf insertions and the rating dates. Large genotypic variation for resistance was found in both the inbred and testcross populations. Genotype-environment interaction and error variances were of minor importance, thus high entry-mean heritabilities were achieved. A tight correlation between the inbreds and their corresponding testcrosses was found (r = 0.88, P = 0.01). Heterosis for resistance was significant (P = 0.05), but not very important. In a seedling test with 20,30 single-pustule isolates, 34 out of 44 inbreds reacted race-specifically. From the remaining inbred lines, three were medium and seven highly susceptible. In a further greenhouse test with 16 inbreds, seven were susceptible and five were resistant in both seedling and adult-plant stages. The remaining four lines had adult-plant resistance. In conclusion, race-specific leaf-rust resistance can be selected among inbred lines per se. Lines should also be tested in the adult-plant stage. [source] Rubisco expression in rice leaves is related to genotypic variation of photosynthesis under elevated growth CO2 and temperaturePLANT CELL & ENVIRONMENT, Issue 12 2003R. W. GESCH ABSTRACT Genetic modifications of agronomic crops will likely be necessary to cope with global climate change. This study tested the hypotheses that genotypic differences in rice (Oryza sativa L.) leaf photosynthesis at elevated [CO2] and temperature are related to protein and gene expression of Rubisco, and that high growth temperatures under elevated [CO2] negatively affect photosystem II (PSII) photochemical efficiency. Two rice cultivars representing an indica (cv. IR72) and japonica type (cv. M103) were grown in 350 (ambient) and 700 (elevated) µmol CO2 mol,1 at 28/18, 34/24 and 40/30 °C sinusoidal maximum/minimum, day/night temperatures in outdoor, sunlit, environment-controlled chambers. Leaf photosynthesis of IR72 favoured higher growth temperatures more than M103. Rubisco total activity and protein content were negatively affected in both genotypes by high temperatures and elevated CO2. However, at moderate to high growth temperatures, IR72 leaves averaged 71 and 39% more rbcS transcripts than M103 under ambient and elevated CO2, respectively, and likewise had greater Rubisco activity and protein content. Expression of psbA (D1 protein of PSII) in IR72 leaves increased with temperature, whereas it remained constant for M103, except for a 20% decline at 40/30 °C under elevated CO2. Even at the highest growth temperatures, PSII photochemical efficiency was not impaired in either genotype grown under either ambient or elevated CO2. Genotypic differences exist in rice for carboxylation responses to elevated CO2 and high temperatures, which may be useful in developing genotypes suited to cope with global climate changes. [source] Isozyme variation under different modes of reproduction in two clonal winter annuals, Sedum rosulato-bulbosum and Sedum bulbiferum (Crassulaceae)PLANT SPECIES BIOLOGY, Issue 2 2008NOZOMI TSUJIMURA Abstract We studied isozyme variation in two annual species that produce bulbils, Sedum rosulato-bulbosum, which includes both sexually reproducing plants and obligate clonal plants that result from triploidy (fertile and sterile S. rosulato-bulbosum, respectively), and an obligate clonal plant, Sedum bulbiferum, to examine the relationship between reproductive mode and isozyme variation. The sterile S. rosulato-bulbosum population exhibited no genotypic variation, but showed high genetic variation (gene diversity, He = 0.60) because five of the six loci that we analyzed were heterozygous. Almost all ramets of S. bulbiferum across 20 populations shared an identical isozyme phenotype, although we could not identify the genetic basis of the phenotype. In contrast, fertile S. rosulato-bulbosum exhibited genotypic variation across the species, but comprised genotypically uniform and polymorphic populations whose genotypic variations correlated positively with the genetic variations within the populations (He at the genet level per population ranged from 0.08 to 0.37). Genetic drift and habitat conditions inhibiting seedling recruitment may have caused this among-population variation. The results for sterile and fertile S. rosulato-bulbosum suggest that exclusive clonal reproduction causes low genotypic variation, but maintains genetic variation within individuals. Factors that affect the maintenance of genetic variation in these plants are discussed on the basis of these findings. [source] Micro-injection of lygus salivary gland proteins to simulate feeding damage in alfalfa and cotton flowers ,ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2005Kenneth A. Shackel Abstract Alfalfa and cotton flowers were pierced with small glass capillaries of an overall size and shape similar to that of Lygus stylets, and injected with small quantities (6 to 100 nL) of solutions that contained Lygus salivary enzymes. Crude and partially purified protein solutions from Lygus heads and isolated salivary glands showed substantial polygalacturonase (PG) activity, as has been previously reported. Following injection with both crude and partially purified protein solutions, as well as with pure fungal and bacterial PGs, flowers of both alfalfa and cotton exhibited damage similar to that caused by Lygus feeding. Injection with the same volume of a buffer control as well as a buffer control containing BSA at a comparable protein concentration (approximately 6 ,g/mL) showed no symptoms. These results are consistent with a previously suggested hypothesis that the extensive tissue damage caused by Lygus feeding is primarily due to the action of the PG enzyme on the host tissue, rather than to mechanical damage caused by the insect stylet. Substantial genotypic variation for a PG inhibiting protein (PGIP) exists in alfalfa and cotton. We, therefore, suggest that breeding and selection for increased native PGIP levels, or transformation with genes encoding PGIP from other plant species, may be of value in obtaining alfalfa and cotton varieties that are more resistant to Lygus feeding damage. Arch. Insect Biochem. Physiol. 58:69,83, 2005. © 2005 Wiley-Liss, Inc. [source] Isozyme variation under different modes of reproduction in two clonal winter annuals, Sedum rosulato-bulbosum and Sedum bulbiferum (Crassulaceae)PLANT SPECIES BIOLOGY, Issue 2 2008NOZOMI TSUJIMURA Abstract We studied isozyme variation in two annual species that produce bulbils, Sedum rosulato-bulbosum, which includes both sexually reproducing plants and obligate clonal plants that result from triploidy (fertile and sterile S. rosulato-bulbosum, respectively), and an obligate clonal plant, Sedum bulbiferum, to examine the relationship between reproductive mode and isozyme variation. The sterile S. rosulato-bulbosum population exhibited no genotypic variation, but showed high genetic variation (gene diversity, He = 0.60) because five of the six loci that we analyzed were heterozygous. Almost all ramets of S. bulbiferum across 20 populations shared an identical isozyme phenotype, although we could not identify the genetic basis of the phenotype. In contrast, fertile S. rosulato-bulbosum exhibited genotypic variation across the species, but comprised genotypically uniform and polymorphic populations whose genotypic variations correlated positively with the genetic variations within the populations (He at the genet level per population ranged from 0.08 to 0.37). Genetic drift and habitat conditions inhibiting seedling recruitment may have caused this among-population variation. The results for sterile and fertile S. rosulato-bulbosum suggest that exclusive clonal reproduction causes low genotypic variation, but maintains genetic variation within individuals. Factors that affect the maintenance of genetic variation in these plants are discussed on the basis of these findings. [source] | |||||||||||||||||||||||||||||||