Ammonia and Nitrous Oxide Emissions after Landspreading of Slurry as Influenced by Application Technique and Dry Matter-Reduction. II. Short Term Nitrous Oxide Emissions

Strategies reducing NH₃ volatilisation from slurry include separation of slurry, special application techniques and additives. We studied the impact of manure separation and application technique on N₂O release after manure application. Untreated and separated cattle slurry (dry matter content of 7.1% and 4.4%, respectively) was applied to winter wheat using broadcast and banded application and injection. The N₂O emissions were measured at high frequency for 14 to 20 days after slurry treatment by the closed chamber method. Manured plots showed significantly higher N₂O emissions than the control plots but neither dry matter reduction of slurry nor application technique significantly influenced the N₂O emissions. The variability of N₂O emission was influenced by the application technique and increased in the order: banded application – injection – broadcast application. There was no correlation between NH₃ losses from applied slurry and N₂O emissions. Thus reducing ammonia volatilisation will not necessarily increase N₂O emissions.     

Simulating the spread of classical swine fever virus between a hypothetical wild-boar population and domestic pig herds in Denmark

Denmark has no free-range wild-boar population. However, Danish wildlife organizations have suggested that wild boar should be reintroduced into the wild to broaden national biodiversity. Danish pig farmers fear that this would lead to a higher risk of introduction of classical swine fever virus (CSFV), which could have enormous consequences in terms of loss of pork exports. We conducted a risk assessment to address the additional risk of introducing and spreading CSFV due to the reintroduction of wild boar. In this paper, we present the part of the risk assessment that deals with the spread of CSFV between the hypothetical wild-boar population and the domestic population. Furthermore, the economic impact is assessed taking the perspective of the Danish national budget and the Danish pig industry. We used InterSpreadPlus to model the differential classical swine fever (CSF) risk due to wild boar. Nine scenarios were run to elucidate the effect of: (a) presence of wild boar (yes/no), (b) locations for the index case (domestic pig herd/wild-boar group), (c) type of control strategy for wild boar (hunting/vaccination) and (d) presence of free-range domestic pigs. The presence of free-range wild boar was simulated in two large forests using data from wildlife studies and Danish habitat data. For each scenario, we estimated (1) the control costs borne by the veterinary authorities, (2) the control-related costs to farmers and (3) the loss of exports associated with an epidemic. Our simulations predict that CSFV will be transmitted from the domestic pig population to wild boar if the infected domestic pig herd is located close to an area with wild boar (<5 km). If an outbreak begins in the wild-boar population, the epidemic will last longer and will occasionally lead to several epidemics because of periodic transfer of virus from groups of infected wild boar to domestic pig herds. The size and duration of the epidemic will be reduced if there are no free-range domestic pig herds in the area with CSF-infected wild boar. The economic calculations showed that the total national costs for Denmark (i.e. the direct costs to the national budget and the costs to the pig industry) related to an outbreak of CSF in Denmark will be highly driven by the reactions of the export markets and in particular of the non-EU markets. Unfortunately, there is a substantial amount of uncertainty surrounding this issue. If hunting is used as a control measure, the average expenses related to a CSF outbreak will be 40% higher if wild boar are present compared with not present. However, a vaccination strategy for wild boar will double the total costs compared with a hunting strategy.     

不同施硼量对油菜叶片中不同形态硼含量的影响

采用盆栽试验研究了不同施硼量对不同生育期不同部位叶片中水溶性硼和全硼含量的影响,并对以水溶性硼代替全硼作为植株营养诊断的方法进行了初步探讨。当施硼量达到5 1kg/hm2,油菜苗期、抽薹期的生物产量以及子粒产量均下降,但叶片中的全硼和水溶性硼含量仍随施硼量的增加而增加。不同生育期和不同部位叶片的全硼含量虽然与施硼量有较好的相关性,但是不同处理之间的差异,特别是过量差异过小,很难用于营养诊断。水溶性硼含量与施硼量也有较好的相关性,而且苗期未完全展开叶片和完全展开叶片的水溶性硼含量可以较敏感地反应油菜的硼营养差异,因此,可以用作硼的营养诊断方法,但是水溶性硼的诊断临界指标需要进一步的研究。     

Accumulation of viral 126 kDa protein and symptom expression in tobacco systemically infected with different strains of tobacco mosaic virus

Tobacco mosaic virus strains W U1, flavum, V4 and masked, which induce symptoms in tobacco ranging from a severe mosaic to virtually no reaction, were used to study relationships between accumulation of viral 126 kDa protein, X-body formation and symptom expression. The RNAs of all strains encode proteins of similar sizes to those of the common strain W U1. Antisera against the coat and 126 kDa proteins of W U1 recognized corresponding proteins of the other three strains.All virus strains accumulated to substantial levels in systemically infected leaves, as evidenced by the presence of coat protein in virus crystals. The 126 kDa protein was localized in large X-bodies associated with nuclei in W U1- and flavum-infected tissue, but in tiny X-bodies, free in the cytoplasm, in masked-infected plants. Neither X-bodies, nor 126 kDa proteins were observed in V4-infected tissue. Since in vitro synthesized 126 kDa protein from V4 was not more sensitive to proteolysis than that from W U1 or flavum, accumulation of the protein in X-bodies in the latter seems to result from excess synthesis. The possibility that the X-bodies are involved in the expression of severe symptoms is discussed.     

Thrips Resistance in Pepper and Its Consequences for the Acquisition and Inoculation of Tomato spotted wilt virus by the Western Flower Thrips

ABSTRACT Different levels of thrips resistance were found in seven Capsicum accessions. Based on the level of feeding damage, host preference, and host suitability for reproduction, a thrips susceptible and a resistant accession were selected to study their performance as Tomato spotted wilt virus (TSWV) sources and targets during thrips-mediated virus transmission. Vector resistance did not affect the virus acquisition efficiency in a broad range of acquisition access periods. Inoculation efficiency was also not affected in short inoculation periods, but was significantly lower on plants of the thrips resistant accession during longer inoculation access periods. Under the experimental conditions used, the results obtained show that transmission of TSWV is little affected by vector resistance. However, due to a lower reproduction rate on resistant plants and a lower preference of thrips for these plants, beneficial effects of vector resistance might be expected under field conditions.     

Molecular evidence for the occurrence of beet western yellows virus on chickpea in Morocco

A luteovirus isolate infecting chickpea in Morocco was experimentally transmitted by Myzus persicae to Physalis floridana, on which it produced mild symptoms. When tested in western blots against antisera to known legume luteoviruses, this isolate reacted strongly to beet western yellows virus (BWYV) antiserum, moderately to bean leafroll virus antiserum, while no reaction was recorded with the antiserum against subterranean clover red leaf virus. In PCR, a fragment of ca. 950 bp was amplified, comprising the 3' end of the open reading frame (ORF) 3, the complete coat protein gene (ORF 4), and the non-translated region in between these ORFs. The nucleotide sequence of the amplified fragment showed high similarity with BWYV (approximately 96%), and lower (50–60%) with other luteoviruses reported to infect legumes. On the basis of these data, the Moroccan isolate was identified as BWYV. This is the first molecular evidence for the occurrence of BWYV on chickpea in Morocco, and on food legumes in general in North Africa.     

Effects of Temperature and Host on the Generation of Tomato Spotted Wilt Virus Defective Interfering RNAs

ABSTRACT The generation of defective interfering (DI) RNA molecules of tomato spotted wilt tospovirus (TSWV) was studied by serially passaging in-ocula from plant to plant under different controlled conditions. DI RNAs were generated at higher rates in plants at 16 degrees C than in plants incubated at higher temperatures. Another factor promoting the TSWV DI RNA generation was the use of high virus concentrations in the inocula. The solanaceous species Capsicum annuum, Datura stramonium, Lycopersicon esculentum, Nicotiana benthamiana, and N. rustica supported the generation of DI RNAs, whereas the virus recovered from the inoculated composite species, Emilia sonchifolia, remained free of any DI RNA under all conditions tested. This study resulted in a strategy to maintain DI RNA-free TSWV isolates, as well as in an efficient way to produce a large population of different DI RNA species. A single DI RNA species usually became dominant in an isolate after a few rounds of serial inoculations. The possible mechanisms involved in TSWV DI RNA generation under different inoculation circumstances are discussed.     

Impeded Thrips Transmission of Defective Tomato spotted wilt virus Isolates

Two defective RNA-containing isolates (Pe-1 and 16-2) and an envelope-deficient (env ) isolate of Tomato spotted wilt virus (TSWV) were tested for their transmissibility by Frankliniella occidentalis. The Pe-1 isolate contained a truncated L RNA segment that barely interfered with symptom expression and replication of the wild-type (wt) L RNA segment. This isolate was transmitted with an efficiency of 51%, a value comparable to that found for wt TSWV (54%). Isolate 16-2, which contained a genuine defective interfering L RNA as concluded from its ability to suppress wt L RNA synthesis and attenuation of symptom expression, was not transmitted at all. The midguts of all larvae that ingested Pe-1 became infected, whereas limited midgut infections were found in 24% of the larvae that ingested 16-2. This difference in infection could be explained by the presence of a low number of infectious units in the inoculum ingested from plants as demonstrated in infection experiments and verified by northern blot analysis. The env isolate failed to infect the midgut after ingestion and could not be transmitted by any thrips stage. This isolate also cannot infect primary thrips cell cultures. Taken together, these results suggest that the envelope of TSWV contains the determinants required for binding and subsequent infection of thrips cells.     

Application of Phage Display in Selecting Tomato spotted wilt virus-Specific Single-Chain Antibodies (scFvs) for Sensitive Diagnosis in ELISA

ABSTRACT A panel of recombinant single-chain antibodies (scFvs) against structural proteins of Tomato spotted wilt virus (TSWV) was retrieved from a human combinatorial scFv antibody library using the novel phage display technique. After subcloning the encoding DNA sequences in the expression vector pSKAP/S, which allowed the scFvs to be expressed as alkaline phosphatase fusion proteins, 17 different scFv antibodies were obtained. Of these, 12 scFvs were directed against the nucleoprotein (N) and 5, putatively, against the glycoproteins (G1 and G2). Five of the N-specific antibodies cross-reacted with two other tospoviruses (Tomato chlorotic spot virus and Groundnut ringspot virus), but none recognized the more distantly related tospoviruses Impatiens necrotic spot virus, Watermelon silverleaf mottle virus, Iris yellow spot virus, or Physalis severe mottle virus. The successful use of one of the antibodies as coating and detection reagent in a double-antibody sandwich enzyme-linked immunosorbent assay showed the potential of the phage display system in obtaining antibodies for routine TSWV diagnosis.