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51.
Partho Pratim Debnath Jerome Delamare-Deboutteville Mona Dverdal Jansen Kornsunee Phiwsaiya Afsana Dalia Md. Abir Hasan Saengchan Senapin Chadag Vishnumurthy Mohan Ha Thanh Dong Channarong Rodkhum 《Journal of fish diseases》2020,43(11):1381-1389
Tilapia lake virus (TiLV) is an emerging pathogen in aquaculture, reportedly affecting farmed tilapia in 16 countries across multiple continents. Following an early warning in 2017 that TiLV might be widespread, we executed a surveillance programme on tilapia grow-out farms and hatcheries from 10 districts of Bangladesh in 2017 and 2019. Among farms experiencing unusual mortality, eight out of 11 farms tested positive for TiLV in 2017, and two out of seven tested positive in 2019. Investigation of asymptomatic broodstock collected from 16 tilapia hatcheries revealed that six hatcheries tested positive for TiLV. Representative samples subjected to histopathology confirmed pathognomonic lesions of syncytial hepatitis. We recovered three complete genomes of TiLV from infected fish, one from 2017 and two from 2019. Phylogenetic analyses based on both the concatenated coding sequences of 10 segments and only segment 1 consistently revealed that Bangladeshi TiLV isolates formed a unique cluster within Thai clade, suggesting a close genetic relation. In summary, this study revealed the circulation of TiLV in 10 farms and six hatcheries located in eight districts of Bangladesh. We recommend continuing TiLV-targeted surveillance efforts to identify contaminated sources to minimize the countrywide spread and severity of TiLV infection. 相似文献
52.
Alberto Pea‐Rodríguez Zo Pelletier‐Morreeuw Jazmín García‐Lujn María del Carmen Rodríguez‐Jaramillo Laura Guzmn‐Villanueva Cristina Escobedo‐Fregoso Dariel Tovar‐Ramírez Ana Gisela Reyes 《Aquaculture Research》2020,51(4):1336-1345
Agave lechuguilla is a succulent plant species, mainly distributed in the northeast of Mexico and south of the United States of America. The main use for this plant is the fibre´s extraction (known as Tampico fibres), resulting in 15% of fibres and 85% of a by‐product waste named guishe. The lechuguilla collectors, normally incinerate the guishe, thus causing environmental contamination. Interestingly, recent studies showed that guishe contains molecules with nutritional properties, such as saponins, flavonoids and sugars. Therefore, in this work, we evaluated the effect of the crude extract of guishe as a feed additive in whiteleg shrimp diets. According to that, MS‐HPLC analysis of the extract showed the presence of saponins such as diosgenin, smilagenin, hecogenin, manogenin, tigogenin hexose, yucagenin, chlorogenin, diosgenin diglucoside and the flavonol, quercetin. After chemical analysis, the crude extract was included into an experimental diet in four levels; 0% (L0%), 0.1% (L0.1%), 0.3% (L0.3%) and 0.6% (L0.6%). Dietary incorporation of the extract was evaluated by zootechnical performance, haemolymph biochemistry, histomorphology and digestive enzyme activity of shrimps. After 5‐week feeding, the L0.3% diet showed significantly higher growth and better feed utilization among treatments. A significant increase in tubule epithelium height and tubule coverage area from hepatopancreas in shrimp under L0.3% diet compared with the control diet suggest an improvement of the health and nutritional status of the shrimp. Inclusion of L0.3% and L0.6% of the crude extract resulted in a reduction in amylase activity, without effect in glucose levels in the haemolymph. Thus, we suggest that lechuguilla guishe crude extract contains nutritional molecules that may be used as a feed additive to promote shrimp productivity. 相似文献
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Homozygous mlo -barley plants are resistant to barley powdery mildew but hypersusceptible to the rice blast fungus Magnaporthe oryzae . A mutational analysis was performed in the barley back-cross line BCIngrid mlo5 which led to the identification of two mutants with enhanced capacity to resist infections by M. oryzae , referred to as enhanced M. oryzae resistance mutants emr1 and emr2 . Here, we report on the characterization of emr2 mutant plants which not only show an almost complete reduction in disease severity after inoculation with M. oryzae but are also resistant to the necrotrophic fungi Drechslera teres and Rhynchosporium secalis . Histological analysis revealed that resistance to M. oryzae was based mainly on the formation of papillae at sites of attempted penetration into epidermal cells. There was no progression of fungal growth into the mesophyll. Additionally, because of the presence of the mlo -allele, emr2 -plants retained resistance to powdery mildew. The emr2 -conditioned broad spectrum resistance was inherited as in a recessive manner. Monitoring of PR -gene expression and enzymatic activity of peroxidases revealed a constitutively activated defence in emr2 . 相似文献
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Laurent J. Lamarque Déborah Corso José M. Torres-Ruiz Eric Badel Timothy J. Brodribb Régis Burlett Guillaume Charrier Brendan Choat Hervé Cochard Gregory A. Gambetta Steven Jansen Andrew King Nicolas Lenoir Nicolas Martin-StPaul Kathy Steppe Jan Van den Bulcke Ya Zhang Sylvain Delzon 《Annals of Forest Science》2018,75(3):88
Key message
Direct, non-invasive X-ray microtomography and optical technique observations applied in stems and leaves of intact seedlings revealed that laurel is highly resistant to drought-induced xylem embolism. Contrary to what has been brought forward, daily cycles of embolism formation and refilling are unlikely to occur in this species and to explain how it copes with drought.Context
There has been considerable controversy regarding xylem embolism resistance for long-vesselled angiosperm species and particularly for the model species for refilling (Laurus nobilis L.).Aims
The purpose of this study was to resolve the hydraulic properties of this species by documenting vulnerability curves of different organs in intact plants.Methods
Here, we applied a direct, non-invasive method to visualize xylem embolism in stems and leaves of intact laurel seedlings up to 2-m tall using X-ray microtomography (microCT) observations and the optical vulnerability technique. These approaches were coupled with complementary centrifugation measurements performed on 1-m long branches sampled from adult trees and compared with additional microCT analyses carried out on 80-cm cut branches.Results
Direct observations of embolism spread during desiccation of intact laurels revealed that 50% loss of xylem conductivity (Ψ50) was reached at ??7.9?±?0.5 and ??8.4?±?0.3 MPa in stems and leaves, respectively, while the minimum xylem water potentials measured in the field were ??4.2 MPa during a moderate drought season. Those findings reveal that embolism formation is not routine in Laurus nobilis contrary to what has been previously reported. These Ψ50 values were close to those based on the flow-centrifuge technique (??9.2?±?0.2 MPa), but at odds with microCT observations of cut branches (??4.0?±?0.5 MPa).Conclusion
In summary, independent methods converge toward the same conclusion that laurel is highly resistant to xylem embolism regardless its development stage. Under typical growth conditions without extreme drought events, this species maintains positive hydraulic safety margin, while daily cycles of embolism formation and refilling are unlikely to occur in this species.58.
John L. Devaney Pádraig M. Whelan Marcel A. K. Jansen 《European Journal of Forest Research》2018,137(1):69-78
Conspecific negative density dependence in tree species can have major consequences for structuring of communities, yet in temperate forests this phenomenon remains largely unexplored. We investigated density-dependent recruitment in the long-lived conifer yew (Taxus baccata L.), for which low levels of regeneration have been linked with reduced light availability beneath conspecific canopies and speculative autotoxic effects. We combined in situ assessment of yew regeneration in a temperate forest in southwest Ireland with ex situ pot experiments to assess whether light and/or beneath conspecific canopy conditions inhibit the germination and early growth of yew. In field experiments, recruitment was related to distance from adult conspecifics, with higher levels of regeneration found in areas not beneath yew canopies. However, reduced light availability beneath the dense yew canopy was not responsible for this pattern, with abundant seedlings found in areas of equivalent or even lower light availability. Pot experiments showed that seedling survival was highest in deep shade treatments. Experiments also demonstrated that the addition of yew needles negatively affected seedling growth, but not seed germination. Together, our results suggest that under natural forest conditions, the absence of regeneration beneath mature yew canopies, often attributed to low light availability, may at least be partly related to substances in yew canopy or leaf leachates. 相似文献
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60.
Knut Wiik Vollset Randi Ingebjørg Krontveit Peder A Jansen Bengt Finstad Bjørn Torgeir Barlaup Ove Tommy Skilbrei Martin Krkošek Pål Romunstad Arnfinn Aunsmo Arne J Jensen Ian Dohoo 《Fish and Fisheries》2016,17(3):714-730
Parasites can, in theory, have large impacts on the survival of fish populations. One method to evaluate such impacts on anadromous species is to apply manipulative field experiments in which parallel groups of antiparasitically treated and non‐treated fish are simultaneously released and then subsequently recaptured as returning adults. A systematic review and meta‐analysis on all such Norwegian studies on Salmo salar provided a data set for the time period 1996 to 2011 on 118 release groups comprising 657 624 fish released and 3989 recaptured. The overall risk ratio (RR) was estimated to be 1.18 (95% CI: 1.07–1.30). The effect varied strongly between groups, (Higgins I2 = 40.1%). Over 70% of this heterogeneity could be explained by the release location, time period and baseline survival. The most important predictor variable was baseline survival. In groups with low recapture in the control group (low baseline survival), the effect of treatment was high (RR = 1.7), while in groups with high recapture in the control group (high baseline survival), there was no effect of treatment (RR ~ 1.00). The most prevalent parasite in the region affected by the drugs administered was Lepeophtheirus salmonis. Hence, the meta‐analysis supports the hypothesis that L. salmonis contributes to the mortality of S. salar during outward migration. However, the effect of treatment was not consistent, but was evidently strongly modulated by other risk factors. The results suggest that the population‐level effects of parasites cannot be estimated independently of other factors affecting the marine survival of S. salar. 相似文献