Prevalence of antibodies to equine viruses in the Netherlands

Summary The prevalence of antibodies to various viruses was investigated in a series of serum samples collected from horses in the Netherlands between 1963 and 1966 and from 1972 onwards. Neutralizing antibodies to equine rhinopneumonitis virus, equine arteritis virus and to equine rhinovirus types 1 and 2 were detected in respectively 76%, 14%, 66% and 59% of the equine serum samples tested. The observed incidence of serum samples positive to equine adenovirus in the complement fixation test was 39%. Precipitating antibodies to equine infectious anaemia virus were detected only in serum samples from two horses imported from abroad. Haemagglutination inhibiting antibodies to Myxovirus influenzae A / equi-1, M. Influenzae A / equi-2, and Reovirus types 1, 2, and 3 were present in respectively 82%, 50%, 10%, 33% and 3.6% of the serum samples tested. The most frequently observed incidence of antibodies to the various equine respiratory viruses occurred in the groups of horses having repeatedly contact with other horses.     

‘Plantibodies’: a flexible approach to design resistance against pathogens

Engineering resistance against various diseases and pests is hampered by the lack of suitable genes. To overcome this problem we started a research program aimed at obtaining resistance by transfecting plants with genes encoding monoclonal antibodies against pathogen specific proteins. The idea is that monoclonal antibodies will inhibit the biological activity of molecules that are essential for the pathogenesis. Potato cyst nematodes are chosen as a model and it is thought that monoclonal antibodies are able to block the function of the saliva proteins of this parasite. These proteins are, among others, responsible for the induction of multinucleate transfer cells upon which the nematode feeds. It is well documented that the ability of antibodies to bind molecules is sufficient to inactivate the function of an antigen and in view of the potential of animals to synthesize antibodies to almost any molecular structure, this strategy should be feasible for a wide range of diseases and pests.Antibodies have several desirable features with regard to protein engineering. The antibody (IgG) is a Y-shaped molecule, in which the domains forming the tips of the arms bind to antigen and those forming the stem are responsible for triggering effector functions (Fc fragments) that eliminate the antigen from the animal. Domains carrying the antigen-binding loops (Fv and Fab fragments) can be used separately from the Fc fragments without loss of affinity. The antigen-binding domains can also be endowed with new properties by fusing them to toxins or enzymes. Antibody engineering is also facilitated by the Polymerase Chain Reaction (PCR). A systematic comparison of the nucleotide sequence of more than 100 antibodies revealed that not only the 3′-ends, but also the 5′-ends of the antibody genes are relatively conserved. We were able to design a small set of primers with restriction sites for forced cloning, which allowed the amplification of genes encoding antibodies specific for the saliva proteins ofGlobodera rostochiensis. Complete heavy and light chain genes as well as single chain Fv fragments (scFv), in which the variable parts of the light (V_L) and heavy chain (V_H) are linked by a peptide, will be transferred to potato plants. A major challenge will be to establish a correct expression of the antibody genes with regard to three dimensional folding, assembly and intracellular location.     

兽药使用环节存在的问题及对策

经过对兽药生产厂家和经营企业几年的整治,尤其是新<兽药管理条例>和<兽药标签和说明书管理办法>出台后,又经过GMP认证,兽药生产经营市场秩序和经营行为得到了一定的规范.但兽药使用环节中却存在诸多的问题,如:违法使用人用药品;违法使用禁用兽药;不执行休药期规定;未建立台帐等等.这些问题的存在,直接导致了动物产品的安全性问题.对此,笔者分析了兽药使用环节存在问题的原因,并对解决这些问题提出了个人观点.     

Salvinia plants in trade: what species are we actually talking about?

Incorrect labelling of plants in trade and misidentification are widespread. Likewise, in trade numerous names are being used for the ornamental aquatic plant known as ‘Kariba weed’, but rarely the correct scientific name Salvinia molesta Mitch. For inspection services of EPPO member countries, correct identification of S. molesta has become important since the species was added to the EPPO A2 List and the List of Union concern in accordance with EU regulation 1143/2014 based on an EPPO Pest Risk Analysis (PRA) for the species. Inspections and a targetted survey of Salvinia plants in trade in the Netherlands were performed and additional material was obtained from wild sources in South Africa, Hungary and the United States. Specimen identification was verified by comparison with the herbarium collection at Naturalis Biodiversity Center in Leiden and with the sequences available in NCBI GenBank database. This paper provides the tools to correctly identity the relevant Salvinia species.     

Chemical disinfectants can reduce potato blackleg caused by ‘Dickeya solani’

Treatments of tubers with chemical disinfectants (70 % ethanol, 1 % sodium hypochlorite, 2 % copper sulphate, 5 % peracetic acid, 10 % hydrogen peroxide, 1 % MennoClean (benzoic acid), 5 % trisodium phosphate and 0.2 % caffeine) were evaluated for control of blackleg caused by ‘D. solani’. All disinfectants effectively killed bacteria in axenic cultures within 5 min and all, except hydrogen peroxide and trisodium phosphate, were able to kill ‘D. solani’ in spiked potato extracts. Treatments with all disinfectants except trisodium phosphate, reduced the pathogen populations on the periderm of tubers previously inoculated by dipping in a suspension of ‘D. solani’, when the disinfectant was applied for at least 15 min. However, in replicated greenhouse experiments, treatments with all disinfectants except hydrogen peroxide and caffeine resulted in phytotoxicity, reducing sprouting of tubers with 10 – 100 %. Sodium hypochlorite and MennoClean were selected for further studies. Treatments of inoculated tubers with these disinfectants prevented developing of soft rot symptoms on tubers when subjected to favourable rotting conditions. In replicated greenhouse experiments, inoculated tubers treated with sodium hypochlorite and MennoClean reduced the blackleg disease incidences from 50 % to 0 % and to 5 %, respectively, and symptomless infection of potato stems from 93 % to 0 % and to 5 %, respectively. A combination of both compounds was highly phytotoxic. The potential use of sodium hypochlorite and MennoClean in an integrated management strategy for potato blackleg is discussed.     

Uptake and metabolism as mechanisms of selective herbicidal activity of the 1,2,4-triazolo[1,5-a] pyrimidines

In order to identify the factors providing the triazolopyrimidines with a wide range of selectivity amongst agriculturally important plant species, studies were made on the uptake and metabolism of a representative compound, N-(2,6-dichlorophenyl)-5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine- 2-sulfonamide. This compound is much more phytotoxic to dicots than to monocots. Experiments showed that variations in leaf morphologies and geometries relative to spray applications resulted in different herbicide dosages applied to plant species used in selectivity evaluations. However, this parameter did not have a statistically significant correlation to herbicide selectivity measurements. Characterization of the metabolic pathways showed that the major herbicide metabolites involved methyl hydroxylation or hydroxylation of the aniline ring followed by glucose conjugation. Since these metabolites were not exclusive to either monocots or dicots, herbicide selectivity does not appear dependent on the pathway of metabolism. Studies on the kinetics of metabolism suggest instead that metabolic rate was important. Monocots metabolized the herbicide rapidly and generally were tolerant while the opposite was true of dicots.     

Classification, nomenclature, and plant pathogenic bacteria - a clarification

ABSTRACT In a recent Letter to the Editor of Phytopathology, proposals were made for endorsement and for rejection of selected names of plant pathogenic Pseudomonas spp. and Xanthomonas spp. We believe that support for, and rejection of, several names was based on misconceptions concerning the Approved Lists of Bacterial Names and entails misinterpretations of several Rules of the International Code of Nomenclature of Bacteria. This letter aims to clarify those misconceptions and misinterpretations.     

Beschadiging door natriumchloraat

Samenvatting Een beschrijving wordt gegeven van de beschadigingsbeelden, die door natriumchloraat worden veroorzaakt bij druif, sla, komkommer, tomaat en bloemkool. Het meest opmerkelijke beeld is een lichter worden van de nerven (vein clearing), later gevolgd door grijs- of bruinkleuring. De gevoeligheid van de verschillende gewassen loopt uiteen. Komkommer is gevoeliger dan de overige gewassen. In het najaar zijn jonge planten gevoeliger dan in de zomer. Verschillende mogelijkheden, waardoor natriumchloraat in de bodem kan terechtkomen, worden besproken. Men kan het herstel van de planten bevorderen door het natriumchloraat zo goed mogelijk uit te spoelen door veel water te geven.Summary In this paper the damage caused by sodium chlorate on grape, lettuce, cucumber, tomato and cauliflower is described. The most common symptom is vein clearing, followed by a grey or brown discoloration.The crops mentioned differ in their sensitivity to sodium chlorate. Cucumber is more sensitive to the damaging effect than the other crops. In autumn young plants are more sensitive than in summer. Several possibilities of contamination of the soil with sodium chlorate are mentioned. Recovery of the plants may be promoted by washing out the sodium chlorate with as much water as possible     

Control of Fusarium Wilt of Radish by Combining Pseudomonas putida Strains that have Different Disease-Suppressive Mechanisms

ABSTRACT Biological control of soilborne plant pathogens in the field has given variable results. By combining specific strains of microorganisms, multiple traits antagonizing the pathogen can be combined and this may result in a higher level of protection. Pseudomonas putida WCS358 suppresses Fusarium wilt of radish by effectively competing for iron through the production of its pseudobactin siderophore. However, in some bioassays pseudobactin-negative mutants of WCS358 also suppressed disease to the same extent as WCS358, suggesting that an, as yet unknown, additional mechanism may be operative in this strain. P. putida strain RE8 induced systemic resistance against fusarium wilt. When WCS358 and RE8 were mixed through soil together, disease suppression was significantly enhanced to approximately 50% as compared to the 30% reduction for the single strain treatments. Moreover, when one strain failed to suppress disease in the single application, the combination still resulted in disease control. The enhanced disease suppression by the combination of P. putida strains WCS358 and RE8 is most likely the result of the combination of their different disease-suppressive mechanisms. These results demonstrate that combining biocontrol strains can lead to more effective, or at least, more reliable biocontrol of fusarium wilt of radish.