Infection of susceptible/tolerant barley genotypes with Barley yellow dwarf virus alters the host plant preference of Rhopalosiphum padi clones depending upon their ability to transmit BYDV

Discovering mechanisms of plant–virus–vector interactions is fundamental to understand their ecology and evolution and to apply this knowledge in plant protection. To study the influence of varying Barley yellow dwarf virus (BYDV) transmission efficiencies on host plant preference of Rhopalosiphum padi (L.) clones, we performed host choice experiments with two barley cultivars (BYDV susceptible cv. ‘Rubina’ and BYDV tolerant cv. ‘Vixen’) including healthy and virus-infected plants. For the susceptible barley cultivar ‘Rubina’, aphid clone R07 (high transmission efficiency) preferred BYDV-infected over healthy host plants after 24 h, while clones D10 (medium transmission efficiency) and R09 (low transmission efficiency) preferred neither host. In contrast, BYDV infection of ‘Vixen’ did not affect the plant’s appeal for aphid clone R07. Host plant access, indicated by ingestion and observed by electrical penetration graph technique for a period of 2 h, was facilitated on BYDV-infected cv. ‘Rubina’ for the clones R07 and D10, whereas an opposite effect was observed for the clone R09. For R07 and R09, the difference was not visible after a period of 5 h. As observed earlier for BYDV-infected wheat, enhanced emission of volatile organic compounds associated with virus-induced attraction was detected for BYDV-infected cv. ‘Rubina.’ It is concluded that host plant preference is possibly linked with a high BYDV transmission efficiency as observed for the clone R07, leading to a fitness advantage of this clone as indicated by early increased ingestion. This advantage is not present on BYDV-tolerant genotypes most likely due to the absence of infection symptoms.

     

Isolation of scFv fragments specific to OmpD of Salmonella Typhimurium

Pork meat is one of the major sources for human infections with Salmonella enterica subspecies enterica serovars. Further, zoonoses caused by S. enterica subspecies enterica serovars are responsible for substantial economical losses in industrial countries. Quick and reliable detection of this infection is urgently needed to improve consumer security. Due to its capability to identify infections independent of the species, a competitive ELISA is the preferable method for the detection of anti-Salmonella antibodies in serum. Recombinant antibody fragments (scFvs) were isolated from the naive human antibody gene library HAL7 by phage display. Recombinant produced outer membrane protein D (OmpD) of Salmonella Typhimurium was used as antigen. The characterization of the isolated single chain Fv (scFv) antibodies was done by enzyme-linked immunosorbent assay (ELISA), immunoblot, sequencing, epitope mapping and size exclusion chromatography (SEC). The detection of anti-OmpD IgGs in swine sera by competitive ELISA was shown in a proof of principle concept. Furthermore, the developed competitive ELISA would be compatible to a recently published DIVA vaccine, allow to distinguish between infected and vaccinated pigs.     

Comparative effect of human urine and ammonium nitrate application on maize (Zea mays L.) grown under various salt (NaCl) concentrations

The present study investigates the effect of urine and ammonium nitrate on maize (Zea mays L.) vegetative growth, leaf nutrient concentration, soil electrical conductivity, and exchangeable‐cations contents under various concentrations of NaCl in a soil substrate. The experiment was arranged in a completely randomized block design with eight replications under greenhouse conditions. The experimental soil substrate was made from a 1 : 1 : 1 volume‐ratio mixture of compost, quartz sand, and silty‐loam soil. Salinity was induced by adding 0, 15, and 30 mL of 1 M NaCl solution per kg of substrate to achieve an electrical conductivity (EC) of 1.3 (S0), 4.6 (S1), and 7.6 (S2) dS m^–1. Nitrogen sources were urine and ammonium nitrate applied at 180 and 360 mg N (kg soil substrate)^–1. Basal P and K were added as mono potassium phosphate in amounts equivalent to 39 mg P and 47 mg K (kg substrate)^–1, respectively. In the S0 treatment, a 3‐fold increase in EC was measured after urine application compared to an insignificant change in ammonium nitrate–fertilized substrates 62 d after sowing. Under saline conditions, application of 360 mg N (kg soil)^–1 as urine significantly decreased soil pH and maize shoot dry weight. At the highest salt and N dose (S2, N360) 50% of urine‐fertilized plants died. Regardless of salinity there was no significant difference between the two fertilizers for investigated growth factors when N was supplied at 180 mg (kg soil)^–1. Leaf N and Ca contents were higher after urine application than in ammonium nitrate–fertilized plants. At an application rate of 180 mg N (kg soil)^–1, urine was a suitable fertilizer for maize under saline conditions. Higher urine‐N dosages and/or soil salinity exceeding 7.6 dS m^–1 may have a deleterious effect on maize growth.     

Iron Poisoning in Piglets Autopsy Findings in Experimental and Spontaneous Cases

An account is given of the autopsy findings in 78 piglets which died from iron poisoning. They belonged to an experimental series which included a further 6 piglets that also died but will not be accounted for here. The experiment was designed to study why iron treatment causes occasional deaths among piglets. The results will be reported in full elsewhere (Tollerz, in press).In 63 piglets, the sows had been fed special experimental diets, and in 8 piglets from a field case where deaths occurred after conventional iron treatment to prevent anaemia, the predominant autopsy finding was waxy degeneration of the skeletal muscles, which appeared irrespective of whether iron dextran or iron dextrin was injected intramuscularly, or whether ferrofumarate or ferous sulphate was given orally. Only one piglet had slight heart-muscle degeneration, and hydropericardium was not present.The remaining 7 piglets received ferrous sulphate orally, which resulted in catarrhal to necrotizing gastroenteritis. Three of these piglets had waxy degeneration of the skeletal muscles, but in the other 4 the musculature was intact, which indicates another mechanism of toxicity than that in the cases of muscle degeneration.     

Renal agenesis in an alpaca cria

A 4-day-old alpaca cria presented for inappetence that responded to symptomatic treatment. The cria re-presented with acute signs of inappetence and azotaemia. The azotaemia persisted despite intravenous fluid therapy. There was no right kidney on ultrasound and there appeared to be perirenal oedema around the left kidney. A diagnosis of right renal agenesis and acute renal failure of the left kidney was made. The cria failed to improve and was euthanased. Necropsy examination confirmed right renal agenesis and agenesis of the right ureter and right renal artery. A section of left kidney submitted for histological examination revealed diffuse, acute, marked tubular degeneration and nephrosis. The cause of the renal failure in the left kidney was not determined.     

Phosphate Amendments to Compost for Improving P Bio-Availability

This study was conducted to investigate changes in P-fractions, bio-available P (CAL-P), citric acid extractable P, acid phosphatase activity and microbial biomass C and N during incubation of mature biogenic compost (MBC), immature biogenic compost (IBC) or immature sheep manure compost (ISC) not amended with P or amended with rock phosphate (RP, 7.6% P) or triple-superphosphate (TSP, 19.5% P). Incubation was performed at 20?°C in darkness under aerobic conditions. Samples were collected for laboratory analysis at the start of incubation (D-0) and after one, six and 26?days during incubation (D-1, D-6, D-26). Addition of soluble P fertilizer (TSP) led to a threefold increase in all P fractions in comparison to compost without TSP; even a “priming effect” could be observed, promoting conversion of non-labile to labile P. Moreover, addition of TSP lowered biological activity, especially acid phosphatase activity (P-ase), due to already high concentrations of readily available P. In general, P fractions (bicarbonate extractable P_i (NaHCO₃-P_i) and bicarbonate extractable P_o (NaHCO₃-P_o) and sodium hydroxide extractable P_o (NaOH-P_o)) increased during incubation until day 6 at the expense of NaOH-P_i fraction, which decreased. Generally, RP-derived P showed little or no effect on P fractions during the entire incubation period and only led to slightly increased CAL-P and Citric-acid-P levels. Fertilizer effects on labile P fractions were most enhanced with ISC. IBC enhanced microbial growth and P-ase, thereby enhancing conversion of labile into moderate labile NaOH-P_o.     

Microbial biomass in arable soils of Germany during the growth period of annual crops

Results from several field studies involving numerous measurements were used to describe the change of soil microbial biomass C (C_mic) and N (N_mic) during the growth period of annual crops (years 1988–1992, 1994, 1995) under the temperate climatic conditions of central Europe. The data were taken from our own investigations as well as from the literature. Only studies with at least eight measurements on one plot during the growth period were used. The total number of farms (cash crop–production farms) was 7, that of experimental plots was 15. The evaluation of these results through regression analysis demonstrated that C_mic and N_mic from the beginning of a year increased only slightly until summer and subsequently decreased until autumn to their initial levels. This increase on an average corresponded to a C assimilation of approx. 100 kg ha^–1 and an N immobilization of approx. 20 kg ha^–1 (30 cm)^–1. The increase in N_mic alone could not explain N immobilization rates frequently observed in different studies using ¹⁵N‐labeled fertilizers. Most of the labeled N that was immobilized (>50 kg N ha^–1) might have accumulated in the matrix of soil organic matter (SOM). Therefore, the changes in microbial biomass may be of less importance for changes in soil N storage as frequently assumed.     

Changes in amino acid enantiomers and microbial performance in soils from a subtropical mountain oasis in Oman abandoned for different periods

An important feature of maintaining the agricultural stability in millennia-old mountain oases of northern Oman is the temporary abandonment of terraces. To analyse the effects of a fallow period on soil microbial performance, i.e. microbial activity and microbial biomass, samples of eight terrace soils abandoned for different periods were collected in situ, assigned to four fallow age classes and incubated for 30 days in the laboratory after rewetting. The younger fallow age classes of 1 and 5 years were based on the records of the farmers recollections, the two older fallow age classes of 10–20 and 25–60 years according to the increase in the d -to- l ratio of valine and leucine enantiomers. The increase in these two ratios was in agreement with that of the d -to- l ratio of lysine. The strongest relationship was observed between the increase in the d -to- l ratio of lysine and the decrease in soil microbial biomass C. However, the most stringent coherence between the increase in fallow age and soil properties was revealed by the decreases in cumulative respiration and net N mineralisation rates with decreasing availability of substrate to soil microorganisms. During the 30-day incubation following rewetting, relative changes in microbial activity (respiration and net N mineralisation) and microbial biomass (C and N) indices were similar in the eight terrace soils on a fallow age-class-specific level, indicating that the same basic processes occurred in all of the sandy terrace soils investigated.     

Genome‐wide association studies in elite varieties of German winter barley using single‐marker and haplotype‐based methods

Genome‐wide association studies (GWAS) became a widely used method to map qualitative and quantitative traits in plants. We compared existing single‐marker and haplotype‐based methods for GWAS with a focus on barley. Based on German winter barley cultivars, four different single‐marker and haplotype‐based methods were tested for their power to detect significant associations in a large genome with a limited number of markers. We identified significant associations for yield and quality‐related traits using the iSelect array with 3886 mapped single nucleotide polymorphism (SNP) markers in a structured population consisting of 109 genotypes. Genome simulations with different numbers of genotypes, marker densities and marker effects were used to compare different GWAS methods. Results of simulations revealed a higher power in detecting significant associations for haplotype‐ than for single‐marker approaches, but showed a higher false discovery rate for SNP detection, due to lack of correction for population structure. Our simulations revealed that a population size of about 500 individuals is required to detect QTLs explaining a small trait variance (<10%).