First isolation of hirame rhabdovirus from freshwater fish in Europe

A rhabdovirus was isolated in cell culture inoculated with tissue material from diseased grayling, Thymallus thymallus (L.), originating from a fish farm affected by a mortality episode in Poland. Diagnostics tests showed that the virus was not related to novirhabdoviruses known in Europe, nor to vesiculovirus‐like species, except perch rhabdovirus (PRhV) with which it shared moderate serological relations. However, RT‐PCR with PRhV probes gave negative results. To identify the virus, a random‐priming sequence‐independent single primer amplification was adopted. Surprisingly, two of the obtained sequences exhibited a high identity (>99%) with hirame rhabdovirus (HIRRV), a novirhabdovirus usually found in fish in marine Asiatic countries, for instance Japan, China and Korea. The full‐length sequence of the phosphoprotein gene (P) demonstrated a higher identity of the present isolate with HIRRV from China compared with the Korean isolate. An identical viral sequence was also found in brown trout, Salmo trutta trutta L., affected by mortalities in a second farm in the same region, after a likely contamination from the grayling farm. To our knowledge, this is the first report of HIRRV in Europe, and in two hosts from fresh water that have not been described before as susceptible species.     

Distribution and genetic diversity of rhizobia nodulating natural populations of Medicago truncatula in tunisian soils

A collection of 299 isolates of rhizobia nodulating Medicago truncatula was isolated from 10 Tunisian soils and was characterized by restriction fragment length polymorphism analysis of polymerase chain reaction (PCR/RFLP) of 16S rRNA gene. Results showed that 227 and 72 isolates were assigned, respectively, to Sinorhizobium meliloti and Sinorhizobium medicae. In 9 out of 10 soils S. meliloti was detected, whereas S. medicae was recovered from only 5 out of 10 soils. The cross-nodulation of three populations of M. truncatula grown on Bulla Regia soil, which contained naturally the two Sinorhizobium species, showed that M. truncatula population collected from Amra site was selective to S. meliloti at least in soil conditions. Forty-eight isolates of each Sinorhizobium species trapped by M. truncatula populations collected from Bulla Regia, Soliman and Rhayet sites on Bulla Regia soil were characterized by repetitive extragenic palindromic-PCR (REP-PCR) and showed a clear distinction between the two Sinorhizobium species and a higher diversity for S. meliloti.     

Combined effects of salinity and phosphorus availability on growth,gas exchange,and nutrient status of Catapodium rigidum

The combined effects of NaCl-salinity and phosphorus deficiency on biomass production, nutritional status, and photosynthetic activity were studied in Catapodium rigidum: an annual Poacea with fodder potential. Plants were grown in hydroponic conditions for 55 days under two phosphorus (P) supply: 5 (low) or 180?µmol KH₂PO₄ (sufficient), in the absence or presence of 100?mM NaCl. Obtained results demonstrated that both salinity and P deficiency treatments applied separately reduced substantially plant growth and CO₂ assimilation rate with a more marked impact of salt stress. Salinity has no substantial effect on both shoot P concentrations and phosphorus acquisition efficiency independently of P availability. The highest decrease in plant growth (?91%) was observed in plants simultaneously submitted to both stresses suggesting an additive effect of the two stresses and that P deficiency increased the susceptibility of C. rigidum to salinity. This may be linked to a significant decrease in potassium acquisition (?95%), K/Na selectivity ratio (?73%), stomatal conductance (?66%), CO₂ assimilation rate (?64%), and shoot water content (66%). Furthermore, plants cultivated under combined salinity and sufficient P supply displayed higher stomatal conductance, CO₂ assimilation rate, K/Na selectivity ratio, and plant growth than plants cultivated under combined effects of salinity and P deficiency. These results suggest that adding P to saline soils could be an alternative for alleviating the negative effects of salinity and may ameliorate salinity tolerance.     

Effects of salt treatment on growth,lipid membrane peroxidation,polyphenol content,and antioxidant activities in leaves of Sesuvium portulacastrum L.

Changes in growth, leaf contents of proline, oxidative stress-related parameters, and phenolic compounds, and antioxidant activities were investigated in the halophyte species Sesuvium portulacastrum L. under saline conditions. Rooted cuttings were individually cultivated in sandy soil. After five weeks of pre-treatment, seedlings were submitted during one month to different salt concentrations ranging from 0 to 800?mM NaCl. The plant growth was significantly improved by salt at 200–600?mM concentration. This trend was associated with (i) the stimulation of photosynthetic activity, (ii) the protection of membrane integrity (leaf MDA content 50% lower than the control), and (iii) higher total antioxidant activity, especially at 400?mM NaCl. At this salt concentration plants accumulated high contents of proline, polyphenols, antocyanins, and carotenoids. These compounds could be implied in the protection of the photosynthetic system and in the improvement of growth. Exposure to 800?mM NaCl impaired significantly photosynthesis, proline, polyphenol, antocyanin, and carotenoid accumulation. Yet, the strong antiradical activity (DPPH) observed at this extreme salinity might partly explain the plant survival. S. portulacastrum could be used in the rehabilitation and the stabilisation of saline or saline arid land. Additionally, under saline conditions, S. portulacastrum accumulate a large amount of proline and exhibits important antioxidant potentialities.     

Non-curative, but prophylactic effects of paromomycin in Histomonas meleagridis-infected turkeys and its effect on performance in non-infected turkeys

Histomonosis (blackhead or infectious enterohepatitis) is a disease of gallinaceous birds, especially of turkeys, and is caused by the protozoan Histomonas meleagridis. Since the ban of all chemoprophylactic and chemotherapeutic products against this disease in the European Union, this parasite causes a considerable amount of economical problems in the poultry industry. Research which could ultimately lead to the discovery of new drugs against this disease is thus highly necessary. Hence, in this study, the efficacy of paromomycin against histomonosis in turkeys was investigated.First, the prophylactic and therapeutic efficacy of this drug against H. meleagridis and its effect on the weight gain of turkeys was determined. Adding paromomycin to the feed (400 ppm as well as 200 ppm paromomycin) or to the drinking water (420 mg paromomycin per liter water, added prior to or on the day of challenge) significantly lowered the mortality rate and the caecal and liver lesion scores after an intracloacal infection compared to infected untreated birds. However, when paromomycin was administered to turkeys in the drinking water after the challenge, no significant differences in mortality or in lesion scores could be observed compared to the infected untreated control group. This demonstrates that paromomycin exerts a purely preventive action against histomonosis in turkeys. Additionally, the weight gain of the treated birds was positively influenced by the use of the drug, as the average weight gain of all treated groups (except for the group treated at the day of first mortality) was significantly higher than that of the untreated control group. Finally, the target site of paromomycin was detected in the SS rRNA gene of H. meleagridis. Consequently, the susceptibility to paromomycin can be correlated to the presence of the binding site of the drug at the 3′ end of the small subunit rRNA gene of the parasite. In conclusion, paromomycin can be used as a new prophylactic measure in the control of histomonosis in turkeys.     

Escherichia coli ghosts or live E. coli expressing the ferri-siderophore receptors FepA, FhuE, IroN and IutA do not protect broiler chickens against avian pathogenic E. coli (APEC)

The aim of this study was to investigate if immunization with the ferri-siderophore receptors FepA, FhuE, IroN and IutA could protect chickens against avian pathogenic Escherichia coli (APEC) infection. The antigens were administered as recombinant proteins in the outer membrane (OM) of E. coli strain BL21 Star DE3. In a first immunization experiment, live E. coli expressing all 4 recombinant ferri-siderophore receptors (BL21(L)) were given intranasally. In a second immunization experiment, a mixture of E. coli ghosts containing recombinant FepA and IutA and ghosts containing recombinant FhuE and IroN was evaluated. For both experiments non-recombinant counterparts of the tentative vaccines were administered as placebo. At the time of challenge, the IgG antibody response for BL21(L) and a mixture of E. coli ghosts containing recombinant FepA and IutA and ghosts containing recombinant FhuE and IroN was significantly higher in all immunized groups as compared to the negative control groups (LB or PBS) confirming successful immunization. Although neither of the tentative vaccines could prevent lesions and mortality upon APEC infection, immunization with bacterial ghosts resulted in a decrease in mortality from 50% (PBS) to 31% (non-recombinant ghosts) or 20% (recombinant ghosts) and these differences were not found to be significant.     

Stimulatory effect on pea of Typha Angustifolia L. extracts and their chemical composition

In this study, the influence of aqueous and organic extracts of different plant parts (flowers, leaves, and stems) of Typha angustifolia on the germination and early seedling growth of field pea (Pisum sativum L.) was evaluated. Chemical composition of extracts of different plant parts of Typha was also determined. Aqueous (20, 40, 60, 80, and 100 g L^?1) and organic extracts (at 0.5, 1, and 2 mg mL^?1) were applied to the seeds of two pea cultivars, Douce de Provence and Lincoln, placed in Petri dishes. Application of extracts had a beneficial effect on germination and early seedling growth of both pea cultivars. However, aqueous extract of leaves showed the most beneficial effect at 60 and 40 g L^?1 for the cultivars Douce de Provence and Lincoln, respectively. The effect could be attributed to the allelochemicals present in the aqueous extracts. Petroleum ether and chloroform extracts of leaves had the most stimulating effect on the germination and early seedling growth of pea. Analysis of Typha extracts indicated the presence of vitamin E in leaves, which could be responsible forthis stimulation. Moreover, Typha leaves also had substantial amount of flavonoids. In conclusion, the allelopathic activity of of Typha was dependent on the plant part, the solvent nature, the concentration of the extracts tested, and on the pea cultivar. Application of leaf extract was the most effective in improving the germination rate and early seedling growth of pea.     

Application of chlorophyll fluorescence for the diagnosis of salt stress in tomato “Solanum lycopersicum (variety Rio Grande)”

To study the response of tomato (Solanum lycopersicum cv. Rio Grande) to salinity, the effect on plant growth, water relations, stomatal conductance and Chlorophyll fluorescence was investigated. Tomato plants were grown in peat culture under controlled conditions and submitted during 28 days to saline stress ranging from 0 to 25, 50, 100, 150 and 200 mM of NaCl. At the end of the experiment period, plant growth was significantly decreased with increasing salinity.