Induction of systemic resistance to Agrobacterium tumefaciens by endophytic bacteria in grapevine

Crown gall disease of grapevine, caused by Agrobacterium tumefaciens, often results in severe economic loss to grape production worldwide. This study demonstrated the ability of the endophytic bacteria Pseudomonas sp. Sn48 and Pantoea sp. Sa14 isolated from domesticated and wild grapevines to induce resistance in both above- and belowground tissues of grapevines infected with A. tumefaciens. Our results provide evidence that both strains can colonize roots and/or shoots. We showed that the strains Pseudomonas sp. Sn48 and Pantoea sp. Sa14 are capable of inducing stilbenic phytoalexin production in grapevine tissues and to further prime plantlets for enhanced phytoalexin production after A. tumefaciens inoculation. We also showed that in the majority of treatments, polyamine accumulation remained unchanged or slightly increased in plantlets treated with Pseudomonas sp. Sn48 and Pantoea sp. Sa14 compared with the control. Our findings indicated that the levels of polyamines remain unchanged or significantly decrease in plantlets treated with endophytic bacteria after A. tumefaciens challenge compared to the control and plantlets treated with individual endophytic bacterial strains. PR1, PR2, and PR4 gene expression levels of plantlets treated with Pseudomonas sp. Sn48 and Pantoea sp. Sa14 significantly increased after A. tumefaciens inoculation. The findings revealed the efficacy of the selected endophytic bacteria in triggering grapevine resistance against A. tumefaciens and the possible use of these strains as an alternative to chemical control methods in grapevine crown gall disease management.     

Cross-resistance patterns to ACCase-inhibiting herbicides conferred by mutant ACCase isoforms in Alopecurus myosuroides Huds. (black-grass), re-examined at the recommended herbicide field rate

BACKGROUND: Target‐site‐based resistance to acetyl‐CoA carboxylase (ACCase) inhibitors in Alopecurus myosuroides Huds. is essentially due to five substitutions (Isoleucine‐1781‐Leucine, Tryptophan‐2027‐Cysteine, Isoleucine‐2041‐Asparagine, Aspartate‐2078‐Glycine, Glycine‐2096‐Alanine). Recent studies suggested that cross‐resistance patterns associated with each mutation using a seed‐based bioassay may not accurately reflect field resistance. The authors aimed to connect the presence of mutant ACCase isoform(s) in A. myosuroides with resistance to five ACCase inhibitors (fenoxaprop, clodinafop, haloxyfop, cycloxydim, clethodim) sprayed at the recommended field rate. RESULTS: Results from spraying experiments and from seed‐based bioassays were consistent for all mutant isoforms except the most widespread, Leucine‐1781. In spraying experiments, Leucine‐1781 ACCase conferred resistance to clodinafop and haloxyfop. Some plants containing Leucine‐1781 or Alanine‐2096 ACCase, but not all, were also resistant to clethodim. CONCLUSION: Leucine‐1781, Cysteine‐2027, Asparagine‐2041 and Alanine‐2096 ACCases confer resistance to fenoxaprop, clodinafop and haloxyfop at field rates. Leucine‐1781 ACCase also confers resistance to cycloxydim at field rate. Glycine‐2078 ACCase confers resistance to all five herbicides at field rates. Only Glycine‐2078 ACCase confers clethodim resistance under optimal application conditions. It may be that Leucine‐1781 and Alanine‐2096 ACCases may also confer resistance to clethodim in the field if the conditions are not optimal for herbicide efficacy, or at reduced clethodim field rates. Copyright © 2008 Society of Chemical Industry     

Hydrogen peroxide scavenging mechanisms are components of Medicago truncatula partial resistance to Aphanomyces euteiches

The biochemical processes underlying the expression of resistance in the roots of Medicago truncatula against Aphanomyces euteiches infection was investigated, with emphasis on oxidative stress. The levels of H₂O₂, superoxide dismutase, peroxidase, ascorbate peroxidase, catalase, soluble phenolics and lignin were measured in the roots of two lines, A17 partially resistant and F83005.5 susceptible to A. euteiches at three infection stages; penetration of the epidermis (1 dpi), colonization of the cortex (3 dpi) and invasion of the root stele (6 dpi). A rapid and large decrease of the H₂O₂ levels in A17 roots occurred. However, in F83005.5 roots, the decrease in H₂O₂ levels was delayed until 3 dpi. In A17 roots, the activities of ascorbate peroxidase, peroxidase and catalase were induced as early as 1 dpi, whereas a general decrease in the activity of the four antioxidant enzymes was observed in F83005.5 roots. The levels of soluble phenolics and lignin were increased in A17 roots at 3 and 6 dpi, respectively. The H₂O₂ levels were negatively correlated to ascorbate peroxidase, catalase and lignin production at 1, 3 and 6 dpi, respectively in A17 roots. Physiological concentrations of H₂O₂ found in M. truncatula infected roots had no detrimental effect on the in vitro growth of this oomycete. Our data suggest that H₂O₂ does not have a direct antimicrobial effect on M. truncatula resistance to A. euteiches, but is involved in cell wall strengthening around the root stele, preventing pathogen invasion of the vascular tissues.     

Usefulness of restriction fragment length polymorphism and spoligotyping for epidemiological studies of Mycobacterium bovis in Madagascar: description of new genotypes

Tuberculosis is highly prevalent in cattle in Madagascar. An epidemiological study based on genotyping of Mycobacterium bovis and its transmission to humans was carried out. The restriction fragment length polymorphism (IS6110 and DR markers) and spoligotyping were used to assess the genetic diversity of strains from different regions of Madagascar. One of these strains was isolated from goat, the other strains were isolated from zebu cattle. Nine IS6110 profiles, 20 DR profiles and 12 spoligotypes were obtained. About 90% of all isolates gave a single IS6110 band at about 1.8 kb. Most strains had the same spoligotype. M. bovis strains commonly lack spacers 39-43, and all Malagasy strains also lacked spacers 3-5, 8-10 and 16. This pattern has not been reported elsewhere. DR was the most discriminatory of the three markers. The patterns obtained with the three markers were combined to identify 34 different genotypes, one of which was found in 35% of the strains. No region-specific M. bovis genotype was identified, but the genotyping of 18 M. bovis strains isolated from patients showed that the human and bovine strains were identical, suggesting possible human contamination from zebu cattle.     

CORRELATION OF RADIOGRAPHIC, ECHOCARDIOGRAPHIC, AND ELECTROCARDIOGRAPHIC SIGNS OF LEFT HEART ENLARGEMENT IN DOGS WITH MITRAL REGURGITATION

Thoracic radiographs of 40 dogs with mitral regurgitation were evaluated for signs of left heart enlargement and classified into three groups based on the degree of left atrial enlargement (mild = group A, moderate = group B, and severe = group C). Echocardiographic enlargement ratios were calculated for the left atrium (LAE_echo), the left ventricle (LVE_echo), and the aorta (AOE_echo) by dividing the measured dimension with the expected dimension normalized for body weight. The incidence of LVH patterns and p-mitrale was recorded on electrocardiograms. With advanced stages of the disease, there was good agreement of the radiographs and echocardiograms with significant differences of the left atrial enlargement ratio between groups. Nine of the 16 dogs from groups A and B, however, had LAE_echo ratios within the normal range. Sixteen dogs with radiographic signs of left ventricular enlargement had normal LVEecho ratios. These disagreements were interpreted as either cardiac enlargement not manifest in the dimensional change measured by the echocardiogram or as overreading of radiographs. The left ventricular wall thickness did not vary significantly between groups. The incidence of p-mitrale was 30%, but this ECG abnormality, when present, reliably identified enlarged left atrial dimensions. Left ventricular hypertrophy patterns of the ECG did not correlate with either the radiographic diagnosis of left ventricular enlargement or the echocardiographic enlargement ratios.     

Diagnosis of gastrointestinal parasites in reptiles: comparison of two coprological methods

Background

Exotic reptiles have become increasingly common domestic pets worldwide and are well known to be carriers of different parasites including some with zoonotic potential. The need of accurate diagnosis of gastrointestinal endoparasite infections in domestic reptiles is therefore essential, not only for the well-being of captive reptiles but also for the owners. Here, two different approaches for the detection of parasite stages in reptile faeces were compared: a combination of native and iodine stained direct smears together with a flotation technique (CNF) versus the standard SAF-method.

Results

A total of 59 different reptile faeces (20 lizards, 22 snakes, 17 tortoises) were coprologically analyzed by the two methods for the presence of endoparasites. Analyzed reptile faecal samples contained a broad spectrum of parasites (total occurence 93.2%, n = 55) including different species of nematodes (55.9%, n = 33), trematodes (15.3%, n = 9), pentastomids (3.4%, n = 2) and protozoans (47.5%, n = 28). Associations between the performances of both methods to detect selected single parasite stages or groups of such were evaluated by Fisher''s exact test and marginal homogeneity was tested by the McNemar test. In 88.1% of all examined samples (n = 52, 95% confidence interval [CI] = 77.1 - 95.1%) the two diagnostic methods rendered differing results, and the McNemar test for paired observations showed highly significant differences of the detection frequency (P < 0.0001).

Conclusion

The combination of direct smears/flotation proved superior in the detection of flagellates trophozoites, coccidian oocysts and nematode eggs, especially those of oxyurids. SAF-technique was superior in detecting larval stages and trematode eggs, but this advantage failed to be statistically significant (P = 0.13). Therefore, CNF is the recommended method for routine faecal examination of captive reptiles while the SAF-technique is advisable as additional measure particularly for wild caught animals and individuals which are to be introduced into captive collections.     

Monosaccharide inhibition of adherence by Pseudomonas aeruginosa to canine corneocytes

The effect of d -galactose, d -mannose, l -rhamnose and dextrose on the adhesion to canine corneocytes by three strains of Pseudomonas aeruginosa was studied in six healthy dogs. Canine corneocytes were collected from the inner aspect of the pinna using adhesive discs (D-Squame®). Half millimetre of bacterial suspension in phosphate-buffered saline (PBS) with or without the addition of a monosaccharide was placed over the corneocyte layer and incubated in moist chambers. Image analysis was used to quantify bacterial adherence to corneocytes. The three strains of Pseudomonas adhered well to canine corneocytes. All monosaccharides tested inhibited the adherence of Pseudomonas to canine corneocytes. The mean reduction in adhesion for individual sugars at a concentration of 0.1% was 40.2% (dextrose), 30.8% ( l -rhamnose), 25.6% ( d -galactose) and 19.4% ( d -mannose). When d -galactose, d -mannose and l -rhamnose were used in combination at 0.1% concentration, the mean reduction in adherence was 52.9%. The monosaccharides studied may have a potential role in the management of Pseudomonas infections in dogs.     

Optimal timing of elective caesarean section in Belgian White and Blue breed of cattle: the calf's point of view

The purpose of this study was to evaluate whether the timing of elective caesarean section (ECS) during parturition affects pulmonary and metabolic adaptation to extra-uterine life in healthy Belgian White and Blue (BWB) calves delivered at term. Vaginal palpation was performed and deliveries divided into six categories of timing for ECS: cervix closed (TECS 1); passive and active cervical dilatation (TECS 2 and TECS 3); full cervical dilatation (TECS 4); spontaneous rupture of allantoic (TECS 5) and amniotic (TECS 6) membranes.One hundred and eighteen BWB calves were examined at birth, 5, 15, 30, 45 and 60 min and 2, 3, 6, 12 and 24 h after birth using the following measurements: physical examination (time between birth and sternal recumbency [T-SR]); heart rate (mHR); arterial blood gas analyses (arterial partial pressure in oxygen [PaO(2)], in carbon dioxide [PaCO(2)], arterial haemoglobin oxygen saturation [SaO(2)], alveolo-arterial difference in oxygen [AaDO(2)]); pulmonary function tests using the oesophageal balloon catheter technique (respiratory rate [RR], total pulmonary resistance [R(L)], dynamic lung compliance [C(Ldyn)], tidal volume [V(T)] and minute volume [V(E)]); arterial and venous blood acid-base balance analyses (arterial and venous pH [pHa and pHv], bicarbonate concentration [HCO(3)a and HCO(3)v], base excess [BEa and BEv]); rectal temperature (RT); jugular venous blood sampling for determination of metabolic variables (blood glucose [G], plasma lactate [L], serum cortisol [C], plasma noradrenaline [NA] and adrenaline [A] concentrations); haematological variables (red blood cell count [RBC], total haemoglobin concentration [Hb], Packed Cell Volume [PCV]) and passive immune transfer variables (total serum protein [TP] and beta(2)gammaglobulin [beta(2)gamma] concentrations).TECS significantly (P or =4 calves, TECS< or =3 calves showed lower PaO(2), SaO(2), V(T), C(Ldyn), RT, G, NA, A, RBC, Hb and TP and higher AaDO(2), RR, V(E). TECS differences progressively decreased and disappeared between 6 and 12 h after birth in TECS 2 and 3 calves but remained up to 24 h in TECS 1 calves. Improved postnatal respiratory and metabolic adaptation in TECS> or =4 calves were mainly related to differences in exposure to labour and subsequent hormonal surge: catecholamines, particularly A, enabled more effective removal of lung liquid and/or release of surfactant which contribute to better gas exchanges and induced greater energy mobilization to maintain adequate body temperature.It was concluded waiting for full cervical dilatation before performing CS should be encouraged because it promotes postnatal respiratory and metabolic adaptation in full-term BWB calves.