Diversity of Brazilian biovar 2 strains of Ralstonia solanacearum

Ralstonia solanacearum is responsible for bacterial wilt disease. Specific and accurate identification of this pathogen is essential for protection of susceptible crops as well as breeding resistant varieties. Historically, R. solanacearum has been classified into biovars based on the use of sugar and alcohol as carbon sources, into races based on its ability to infect different hosts, more recently into phylotypes based on the intergenic transcribed sequence of the ribosomal RNA genes 16S and 23S and into sequevars based on the endoglucanase gene (egl) sequence. Race 3 biovar 2 (R3Bv2) is widespread in South and Central America, and in Brazil it is present in all potato-producing regions as the most prevalent strain. In this study, we classified 53 Brazilian R. solanacearum biovar 2 (Bv2) strains by traditional and molecular methods. PCR with specific primers confirmed all 53 bacterial strains as belonging to the R. solanacearum species complex, and all were classified as biovar 2A or 2T based on acidification of sugars and alcohols. Multiplex phylotype PCR assigned all strains to phylotype II. Phylogenetic analysis of egl sequences showed that most Bv2 strains from Brazil analyzed in this study did not cluster with known sequevars and are less clonal than the R3Bv2 strains reported for other countries. This is the first study to address the diversity of a collection of Brazilian R. solanacearum strains using the phylotype and sequevar classification scheme.     

Potential fungal inhibition by immobilized hydrolytic enzymes from Trichoderma asperellum

The use of cell wall degrading enzymes from Trichoderma asperellum immobilized on biodegradable support is an alternative for food packaging. In this study, hydrolytic enzymes produced by T. asperellum were tested as a fungal growth inhibitor, in free form or immobilized on a biodegradable film composed of cassava starch and poly(butylene adipate-co-terephtalate) (PBAT). The inhibitory activity was tested against Aspergillus niger , Penicillium sp., and Sclerotinia sclerotiorum , microorganisms that frequently degrade food packaging. The use of chitin as carbon source in liquid medium induced T. asperellun to produce N-acetylglucosaminidase, β-1,3-glucanase, chitinase, and protease. The presence of T. asperellun cell wall degradating enzymes (T-CWD) immobilized by adsorption or covalent attachment resulted in effective inhibition of fungal growth. The enzymatic activity of T-CWD was stronger on S. sclerotiorum than on the Aspergillus or Penicillum isolates tested. These results suggest that T-CWD can be used in a free or immobilized form to suppress fungi that degrade food packaging.     

Numerical simulation of atmospheric transport of Phakopsora pachyrhizi urediniospores in South America using the state of Paraná-Brazil as a model

European Journal of Plant Pathology - Phakopsora pachyrhizi is a biotrophic fungus that needs living plant tissue in order to survive. The fungus causes Asian rust on soybean and costs billions of...     

Comparative evaluation of experimental challenge by intraperitoneal injection and cohabitation of Atlantic salmon (Salmo salar L) after vaccination against Piscirickettsia salmonis (EM90‐like)

The Chilean aquaculture has been challenged for years by piscirickettsiosis. A common prophylactic measurement to try to reduce the impact from this disease is vaccination, but the development of vaccines that induce satisfactory protection of the fish in the field has so far not been successful. Experimental challenge models are used to test vaccine efficacy. The aim of this study was to evaluate the performance of experimental vaccines after challenge by the two most widely used challenge routes, intraperitoneal injection and cohabitation. A total of 1,120 Atlantic salmon were vaccinated with non‐commercial experimental vaccines with increasing amounts of an inactivated Piscirickettsia salmonis EM90‐like isolate. Differences in mortality, macroscopic and microscopic pathological changes, bacterial load and immune gene expression were compared after challenge by different routes. The results revealed a similar progression of the diseases after challenge by both routes and no gross differences reflecting the efficacy of the vaccines could be identified. The analysis of the immune genes suggests a possible suppression of the cellular immunity by CD8 T cell and with this stimulation of bacterial survival and replication. Comparative studies of experimental challenge models are valuable with regard to identifying the best model to mimic real‐life conditions and vaccines’ performance.     

Soil Enzymatic Activity in Eucalyptus Grandis Plantations of Different Ages

Eucalyptus plantations have become increasingly common in Latin America. However, because Eucalyptus is an exotic species, its presence has raised concerns about changes in the environment, especially to soil properties. The objective of this study was to investigate possible changes in selected soil enzyme activity after several years of Eucalyptus cultivation. Soil samples were collected from four locations: a native forest (Atlantic Forest) used as a reference for the original soil conditions and three E. grandis plantations aged 2, 3 and 5 years, established in 2008, 2007 and 2005, respectively. The native vegetation had been removed and the soil graded and ploughed to establish these plantations. We evaluated soil enzymatic activities (β‐glucosidase, acid phosphatase, dehydrogenase, urease and arylsulfatase) at each location. The activity of β‐glucosidase, phosphatase, dehydrogenase and urease was improved after 5 years, whereas arylsulphatase was impacted negatively. The multivariate analysis showed that the majority of enzyme activities reached the values observed in native forest after the third year of reforestation. The activity of β‐glucosidase was crucial in differentiating the area with 2 years of reforestation from the native forest. The removal of native vegetation in order to establish commercial plantations raises concerns about the real impacts of this practice on the soil. In the present study, plantations of Eucalyptus improved most of the selected enzyme activities after the third year of reforestation. Copyright © 2015 John Wiley & Sons, Ltd.     

The genetic diversity of wild grapes in Mexico

Genetic Resources and Crop Evolution - This is the first report evaluating the genetic diversity of Mexican grape species utilizing DNA-based markers to understand the distribution of grape...     

Comparison of three anaesthetic protocols in Bennett’s wallabies (Macropus rufogriseus)

ObjectiveInvestigate physiological and sedative/anaesthetic effects of xylazine, medetomidine or dexmedetomidine combined with ketamine in free-ranging Bennett's wallabies.Study designProspective clinical trial.AnimalsTwenty-six adult free-ranging Bennett's wallabies.MethodsAnimals were darted intramuscularly with one of three treatments: xylazine and ketamine, 2.0 and 15.0 mg kg^?1, respectively (XK): medetomidine and ketamine 0.1 and 5.0 mg kg^?1 (MK) and dexmedetomidine and ketamine 0.05 and 5.0 mg kg^?1 (DMK). Body weights were estimated. If the animal was still laterally recumbent after 45 minutes of anaesthesia, then an alpha-2 adrenoceptor antagonist, atipamezole, was administered (XK: 0.4 mg kg^?1, MK: 5 mg kg^?1, DMK: 2.5 mg kg^?1). Heart rate (HR) and respiratory rate (f_R) were recorded at 5-minute intervals and temperature at 10-minute intervals. Venous blood was taken 30 minutes after initial injection. Statistical analysis utilized anova. p < 0.05 was considered significant.ResultsAnimals became recumbent rapidly in all groups. XK animals had muscle twitches, responded to external stimuli, and three animals required additional dosing; this was not observed in the MK and DMK groups. HR (mean ± SD beats minute^?1) in XK (81 ± 4) was significantly higher than MK (74 ± 2) and DMK (67 ± 4). There were no differences in f_R, temperature, blood-gas and biochemical values between groups. More animals in MK (9/10) and DMK (5/6) needed antagonism of anaesthesia compared with XK (1/10). There were no adverse effects after anaesthesia.Conclusion and clinical relevanceCardio-respiratory effects were similar in all groups. There were fewer muscle twitches and reactions to external stimuli in MK and DMK. Duration of anaesthesia was shorter in XK; most animals in MK and DMK needed atipamezole to assist recovery. All three treatments provided satisfactory sedation/anaesthesia and are suitable for use in Bennett's wallabies.     

Evaluation of medetomidine-ketamine and dexmedetomidine-ketamine in Chinese water deer (Hydropotes inermis)

ObjectiveTo investigate physiological and sedative/immobilization effects of medetomidine or dexmedetomidine combined with ketamine in free-ranging Chinese water deer (CWD).Study designProspective clinical trial.Animals10 free-ranging adult Chinese water deer (11.0 ± 2.6 kg).MethodsAnimals were darted intramuscularly with 0.08 ± 0.004 mg kg^?1 medetomidine and 3.2 ± 0.2 mg kg^?1 ketamine (MK) or 0.04 ± 0.01 mg kg^?1 dexmedetomidine and 2.9 ± 0.1 mg kg^?1 ketamine (DMK) If the animal was still laterally recumbent after 60 minutes of immobilization, atipamezole was administered intravenously (MK: 0.4 ± 0.02 mg kg^?1, DMK: 0.2 ± 0.03 mg kg^?1). Heart rate (HR) respiratory rate (f_R) and temperature were recorded at 5-minute intervals. Arterial blood was taken 15 and 45 minutes after initial injection. Statistical analysis was performed using Student’s t-test or anova. p < 0.05 was considered significant.ResultsAnimals became recumbent rapidly in both groups. Most had involuntary ear twitches, but there was no response to external stimuli. There were no statistical differences in mean HR (MK: 75 ± 14 beats minute^?1; DMK: 85 ± 21 beats minute^?1), f_R (MK: 51 ± 35 breaths minute^?1; DMK; 36 ± 9 breaths minute^?1), temperature (MK: 38.1 ± 0.7 °C; DMK: 38.4 ± 0.5 °C), blood gas values (MK: PaO₂ 63 ± 6 mmHg, PaCO₂ 49.6 ± 2.6 mmHg, HCO₃^? 30.8 ± 4.5 mmol L^?1; DMK: PaO₂ 77 ± 35 mmHg, PaCO₂ 45.9 ± 11.5 mmHg, HCO₃^? 31.0 ± 4.5 mmol L^?1) and biochemical values between groups but temperature decreased in both groups. All animals needed antagonism of immobilization after 60 minutes. Recovery was quick and uneventful. There were no adverse effects after recovery.Conclusion and clinical relevanceBoth anaesthetic protocols provided satisfactory immobilisation. There was no clear preference for either protocol and both appear suitable for CWD.