Triazine herbicide resistance in Chenopodium album L.: Occurrence and characteristics of an intermediate biotype

Intermediate (I) biotypes for triazine herbicide resistance in Chenopodium album (as defined by a peculiar fluorescence curve), had the same ID₅₀ values as resistant(R) plants for chloroplast response to atrazine, but proved to be more susceptible at lower doses. Furthermore, the lethal dose in seedling treatments was lower than that of the R plants, but six times higher than for susceptible (S) plants. These I characteristics of I biotypes were maternally inherited in crosses. I biotypes were isolated from various progenies of susceptible precursor (Sp) plants in two garden populations. This could be the first step in the occurrence of triazine herbicide resistance. However, Sp plants have not been observed in field populations. The significance of the presence of a single isozyme pattern for all Sp plants is discussed. The results suggest an evolutionary pathway from S to R plants via I biotypes.     

Differences in temperature requirements between Polymyxa sp. of Indian origin and Polymyxa graminis and Polymyxa betae from temperate areas

The temperature requirements of three single cystosorus strains of Polymyxa sp. from India were studied at 15–18, 19–22, 23–26 and 27–30 °C (night-day temperature), and compared with the temperature requirements of three strains of P. graminis from Belgium, Canada and France and two strains of P. betae from Belgium and Turkey. Sorghum was used as the host-plant for the Indian strains; the strains of P. graminis and P. betae from temperate areas were cultivated on barley and sugar beet, respectively. The cystosori germination and the development of plasmodia, zoosporangia and cystosori of Polymyxa sp. from India were optimal at 27–30 °C. Infection progression was slower at 23–26 °C than at 27–30 °C. At 19–22 °C, infection was insignificant. No infection occurred below 19 °C. In contrast, the infection of barley with P. graminis strains from temperate areas was optimal at 15–18 °C, but at 19–22 °C the progression appeared inconsistent and infection stayed low. Above 22 °C, infection was insignificant. P. betae strains showed consistent infection in the range of 15–18 °C to 27–30 °C. Plasmodia formation and cystosori detection of the Belgian strain were slightly advanced at 23–26 °C compared to 19–22 °C but clearly restrained at 27–30 °C. Fungus development of the P. betae strain from Turkey was almost as high at 27–30 °C as at the lower temperatures. These results strengthen the case for distinguishing between Polymyxa sp. from India and P. graminis or P. betae from temperate areas.     

Role of Bordetella bronchiseptica adenylate cyclase in nasal colonization and in development of local and systemic immune responses in piglets

Two Bordetella bronchiseptica mutants, lacking the adenylate cyclase (Cya) or both Cya and pertactin (Prn), were compared with their parental strain NL1013 in their abilities to colonize the nose of neonate piglets and to induce local and systemic antibody responses against filamentous hemagglutinin (FHA) after intranasal (i.n.) inoculation. The number of bacteria recovered and the duration of infection in the nasal secretions were greater for the wild-type parent strain than for the Cya-deficient mutant, indicating that Cya plays an important role during B. bronchiseptica colonization of the nasal cavity. The double mutant did not colonize the nasal cavity and was less able to adhere to epithelial cells in vitro than the other two strains, supporting the hypothesis that Prn plays a major role in cell adhesion. In piglets inoculated with the wild type strain, anti-FHA IgM was found in the nasal secretions one week after inoculation, followed two weeks later by anti-FHA IgA; their presence was concomitant with decreases in bacterial counts. Anti-FHA IgG appeared at six weeks after infection in the serum. In contrast, i.n. inoculation with either mutant failed to induce a nasal secretory antibody response but did induce an earlier and higher IgM response in the serum than inoculation with the wild type strain. However, only the Cya-deficient mutant was able to prime the piglets for the development of a secondary nasal IgM and serum IgG response to FHA after intranasal inoculation with the wild type B. bronchiseptica.     

Growth Effects of Governmental Policies: A Comparative Analysis in a Multi‐Country Context

The potential interactions among governmental policies, investments andeconomic growth are complex and manifold. This paper will perform a systematic comparative analysis of the various economic insights that are currently available on these complex relationships, both theoretically (by a selective literature review) and empirically (by reviewing the empirically obtained insights). Despite the wide variety of potential theoretical relationshipsbetween government expenditures, taxation and growth, most empirical analyses are restricted to simple linear regressions of growth on some measure of government expenditures. We will indicate directions for future empirical research that may enrich our knowledge about the complex relationship between fiscal policies and economic growth, not only nationally but also regionally.     

Fallow residue management effects on upland rice in three agroecological zones of West Africa

Improving fallow quality in upland rice-fallow rotations in West Africa through the site-specific use of leguminous cover crops has been shown to sustain the productivity of such systems. We studied the effects of a range of residue management practices (removal, burning, mulching and incorporation) on fallow biomass and N accumulation, on weed biomass and yield response of upland rice and on changes in soil physical and chemical characteristics in 2-year field trials conducted in three agroecological zones of Côte d'Ivoire. Across fallow management treatments and agroecological zones, rice yields were on average 20–30% higher in legume than in natural fallow plots. Weed biomass was highest in the savanna zone and lowest in the bimodal forest and tended to be less following a legume fallow. Regardless of the type of fallow vegetation and agroecological zone, biomass removal resulted in the lowest rice yields that varied from 0.5?t ha^–1 in the derived savanna zone to 1.5?t ha^–1 in the Guinea savanna zone. Burning of the fallow vegetation significantly increased yield over residue removal in the derived savanna (0.27?t ha^–1, P<0.05) and bimodal forest zones (0.27?t ha^–1, P<0.01), but not in the Guinea savanna. In both savanna environments, residue incorporation was superior to the farmers' practice of residue removal and rice yield increases were related to amounts of fallow N returned to the soil (r²=0.803, P<0.01). In the forest zone, the farmers' practice of residue burning produced the highest yield (1.43?t ha-1 in the case of legumes) and resulted in the lowest weed biomass (0.02?t ha^–1). Regardless of the site, improving the quality of the fallow or of its management had no significant effects on either soil physical or soil chemical characteristics after two fallow cycles. We conclude that incorporation of legume residues is a desirable practice for rice-based fallow rotation systems in savanna environments. No promising residue management alternatives to slash-and-burn were apparent for the forest zone. Determining the possible effects on soil productivity will require longer-term experiments.     

中国部分杂交稻和常规早籼、晚粳品种(系)的抗瘟性

 选用来自中国18个省、市,12个小种分属于9个不同谱系的30个具有广谱毒性的稻瘟病菌株,人工接种于已知抗瘟基因型的品种(系)及中国20世纪90年代新育成的部分杂交稻和常规早籼、晚粳品种上进行水稻抗病性鉴定。通过具有广谱毒性并能识别抗病基因的30个菌株,与具有不同抗性类型并携带有不同或与之相连锁的抗性基因的品种及已知抗性基因的国际鉴别品种进行比较,以期推测某些中国品种的抗性基因。结果表明,部分优异抗瘟材料及新育成的杂交稻组合和常规早籼、晚粳稻品种(系)能抗多数近年采集分离的田间致病菌株,是育种和大面积推广种植     

O157:H7 and O104:H4 Vero/Shiga toxin-producing Escherichia coli outbreaks: respective role of cattle and humans

ABSTRACT: An enteroaggregative Verotoxin (Vtx)-producing Escherichia coli strain of serotype O104:H4 has recently been associated with an outbreak of haemolytic-uremic syndrome and bloody diarrhoea in humans mainly in Germany, but also in 14 other European countries, USA and Canada. This O104:H4 E. coli strain has often been described as an enterohaemorrhagic E. coli (EHEC), i.e. a Vtx-producing E. coli with attaching and effacing properties. Although both EHEC and the German O104:H4 E. coli strains indeed produce Vtx, they nevertheless differ in several other virulence traits, as well as in epidemiological characteristics. For instance, the primary sources and vehicles of typical EHEC infections in humans are ruminants, whereas no animal reservoir has been identified for enteroaggregative E. coli (EAggEC). The present article is introduced by a brief overview of the main characteristics of Vtx-producing E. coli and EAggEC. Thereafter, the O104:H4 E. coli outbreak is compared to typical EHEC outbreaks and the virulence factors and host specificity of EHEC and EAggEC are discussed. Finally, a renewed nomenclature of Vtx-producing E. coli is proposed to avoid more confusion in communication during future outbreaks and to replace the acronym EHEC that only refers to a clinical condition.     

Connection of growth and wood density with wood anatomy in downy birch grown in two different soil types

Soil affects the anatomy of downy birch wood (Betula pubescens), which raises the question whether the growth of this species differs between mineral and peat soils. The aim of this study was to compare growth, density and structure of xylem of B. pubescens between trees grown in different soils. Both growth and density differed between trees grown in different soils. All measured anatomical characteristics, except double thickness of fibre walls, percentage vessel area and ray number, showed differences between the soil types: the cell dimensions were larger and numbers smaller in trees grown in mineral soil. In peat, high growth rates decreased the wall:lumen ratio of fibres in maturing wood, while no such correlation was observed in trees grown in mineral soil at any studied cambial age. In addition, axial parenchyma may have a different role in trees grown in different soils, as the rapid growth decreased and increased axial parenchyma in mineral and peat soil, respectively. The characteristics affecting wood strength were more similar between trees grown in different soils than those affecting water conductance. The observed differences between trees grown in different soils emphasise rapid growth particularly at young ages and shorter reasonable rotation period in mineral soil.