Potato Late Blight and Tuber Yield: Results from 30 Years of Field Trials     

Lars Wiik 《Potato Research》2014,57(1):77-98

During 1983–2012, three field trials per year were performed in each of the three southernmost counties in Sweden to test different fungicide programmes aiming to control late blight, primarily in the very susceptible potato cultivar Bintje. A dataset with results from these field trials was used (i) to examine possible changes in the appearance and behaviour of late blight attack over the years, (ii) to investigate the relationship between late blight in foliage and tuber blight, (iii) to investigate the relationship between late blight and tuber yield and (iv) to identify any correlations between different variables in the dataset. Late blight reached epidemic proportions, i.e. 75% disease severity in the untreated control, in the majority of the field trials. The estimated first attack of late blight was earlier in many field trials after 1998. Differences between years and regions were great in terms of date of the first attack and how the attack developed during the season. For example, in 2002–2005 and 2007, the first attack occurred 40–55 days after planting (DAP), compared with 95–108 DAP in 1994 and 1996. In 1994, 2006 and 2009–2011, the attacks increased from first symptoms to 65% disease severity in the untreated control within 16–21 days, compared with 35–40 days in 1995, 1999 and 2002. The relationship between foliage late blight and tuber blight was weak with the best match found at high disease severity late in the growing season (r?=?0.33; p?<?0.001). The relationship between blight-free tuber yield and start of the first attack indicated a yield increase of 287 kg/day (R ²?=?0.27) for every day’s delay in first attack. Using the DAP for 65% disease severity in the untreated control improved the correlation (R ²?=?0.64) and indicated a yield increase of 534 kg/day for every day’s delay in first attack. The later the onset of attack, the higher the blight-free tuber yield in treated plots. In general, significant correlations were found between blight-free tuber yield, size fractions of tuber yield, date of first late blight attack, date of different degrees of disease severity, disease severity, date of treatment, treatment measures and maintenance.  相似文献   

Nonlocal wind-driven fjord–coast advection and its potential effect on plankton and fish recruitment     

Lars Asplin  Anne Gro Vea Salvanes  & Jon Bent Kristoffersen 《Fisheries Oceanography》1999,8(4):255-263

The Bergen Ocean Model (BOM), a three-dimensional physical coastal ocean model, was used for a numerical simulation experiment to investigate short-term effects of wind-generated coastal upwelling and downwelling on the dynamics of adjacent large outer and smaller inner fjords. The effect of the real alongshore wind regime on advection for an idealized fjord topography, resembling Masfjorden, western Norway, is used as an example. This modelling exercise is a supplement to, and its predictions support, the various hypotheses investigated in ecosystem simulation studies of the Masfjorden. The model predicts that coastal winds from the north cause upwelling and transport the upper water layer out from the fjords. Winds from the south cause downwelling and transport the upper water layer into the fjords. The transport is rapid and ≈50% of the upper water layer may be replaced within 1–2 days. Implications of these physical processes for the dispersal and retention of planktonic organisms and the early life stages of fish are discussed. If strong southerly winds occur frequently, this will transport planktonic organisms into the fjord and may increase the carrying capacity for planktivorous fish. In contrast, frequent strong northerly winds may reduce the abundance of planktonic organisms, including the early life stages of marine fish, and thus possibly reduce recruitment to fjord fish populations. Frequent shifts between southerly and northerly winds would cause an exchange of early life stages between neighbouring fjords and thus enhance genetic exchange.  相似文献   

The influence of anaerobic muscle activity,maturation and season on the flesh quality of farmed turbot     

Bjorn Roth  Albert Imsland  Lars Helge Stien  Rian Schelvis-Smit  Snorri Gunnarsson  Atle Foss 《Aquaculture International》2010,18(3):461-474

In order to test seasonal, rearing, maturing and anaerobic muscle activity effect on the flesh quality of turbot (Scophthalmus maximus) a total of 80 farmed turbot from three different strains from reared under natural or continuous light were killed by a percussive blow to the head in November (winter, Icelandic strain), March (spring, Portuguese strain) and June (summer, domesticated strain (France turbot)). To test the effect of anaerobic muscle activity, 10 fish were on each occasion pre rigor filleted, where one fillet was used as a control, while the other fillet was electrically stimulated using a squared 5 Hz, 10 V pulsed DC for 3 min. All pre rigor fillets were measured for pH, weighed, wrapped in aluminum foil and stored in polystyrene boxes with ice. After 7 days of storage the fillets were measured instrumentally for pH, drip loss, colour (CIE L* a* b*) and texture properties such as hardness and shear force, while fillet shrinkage and colour (RBG) were evaluated with computer imaging on photographs from a standard lightbox. Results showed that softness of the flesh was mainly influenced by factors associated with growth, such as season, photoperiod and maturation. Anaerobic muscle activity simulated with electrical stimulation caused an increase in drip loss (<1%) and loss of shear force (<4%), but had no effect on hardness or fillet shrinkage. Computer imaging revealed that muscle contractions related to the electrical stimulus forced out blood from the fillet causing less reddishness for the entire storage period. We conclude that a pH drop upon slaughter associated with anaerobic muscle activity has a minor effect on the flesh quality in the short run, while seasonal/alternatively genetic effects are predominant.  相似文献   

Performance and welfare of Atlantic salmon,Salmo salar L. post-smolts in recirculating aquaculture systems: Importance of salinity and water velocity     

Trine Ytrestøyl  Harald Takle  Jelena Kolarevic  Sara Calabrese  Gerrit Timmerhaus  Bjørn O. Rosseland  Hans C. Teien  Tom O. Nilsen  Sigurd O. Handeland  Sigurd O. Stefansson  Lars O. E. Ebbesson  Bendik F. Terjesen 《Journal of the World Aquaculture Society》2020,51(2):373-392

Producing a larger post-smolt in recirculating aquaculture systems (RAS) could shorten the production time in sea cages and potentially reduce mortality. Knowledge of the biological requirements of post-smolts in closed-containment systems is however lacking. In the present study, the effects of salinity and water velocity on growth, survival, health, and welfare of Atlantic salmon reared in RAS were examined. Salmon smolts were stocked in three separate RAS with salinities of 12, 22, and 32‰ and subjected to high (1.0 body lengths per s⁻¹) or low (0.3 body lengths second⁻¹) water velocity. Growth performance, survival, welfare, and physiological stress responses were monitored until the fish reached a bodyweight of around 450 g. Growth rate was higher at lower salinity and higher water velocity generally had a positive effect on growth in all salinities. Feed conversion ratio was lower at 12‰ compared to the 22 and 32‰ when the fish were between 250 and 450 g. Higher mortality, elevated plasma cortisol levels, higher incidence of cataract, and a higher expression of stress-induced genes in the skin (iNOS, Muc5ac-like) indicated a negative effect of higher salinity on fish welfare. Male maturation was low (<1%), and not affected by salinity or water velocity.  相似文献   

The importance of Southern Ocean frontal systems for the improvement of body condition in southern elephant seals     

Samantha A. Gordine  Michael A. Fedak  Lars Boehme 《水产资源保护:海洋与淡水生态系统》2019,29(Z1):283-304

DNA‐analysis to monitor fisheries and aquaculture: Too costly?     

Jann Th. Martinsohn  Paul Raymond  Trey Knott  Kevin A. Glover  Einar Eg Nielsen  Lars Bonde Eriksen  Rob Ogden  John Casey  Jordi Guillen 《Fish and Fisheries》2019,20(2):391-401

Evidence from DNA‐analysis is commonplace in human criminal investigations, and while it is increasingly being used in wildlife crime, to date, its application to control and enforcement activities in fisheries and aquaculture has only been sporadic. Contemporary DNA‐analysis tools are capable of addressing a broad range of compliance issues, species identification, mislabelling of fish products, determining the origin of catches and the farm of origin of aquaculture escapees. Such applications have the potential to ensure traceability along the fish product supply chain and to combat consumer fraud and Illegal, Unreported and Unregulated fishing. Nevertheless, DNA‐analysis is not yet used routinely in investigations into compliance with fisheries and aquaculture legislation. One potential reason for this is that DNA‐analysis techniques may have been regarded as too expensive. However, costs have plummeted over the past decade prompting us to objectively assess whether the costs associated with routine use of DNA‐analysis techniques for fisheries and aquaculture control and enforcement activities do constitute an impediment. Based on a number of recent fisheries and aquaculture compliance investigations that incorporated DNA‐analysis, our results indicate that the use of genetic analysis was justified and worthwhile in all cases examined. We therefore conclude that the costs associated with DNA‐analysis do not represent a barrier to the routine adoption of DNA‐analysis techniques in fisheries and aquaculture compliance investigations. Thus, control and enforcement agencies should be encouraged to use such techniques routinely.  相似文献   

The effect of cell density on biomass and fatty acid productivity during cultivation of Rhodomonas salina in a tubular photobioreactor     

Christina Thoisen  Jakob Skov Pedersen  Lars Jrgensen  Anker Kuehn  Benni Winding Hansen  Sren Laurentius Nielsen 《Aquaculture Research》2020,51(8):3367-3375

The microalga Rhodomonas salina is widely used in aquaculture. There is a need for optimization of the growth of the microalgae and its content of essential fatty acids. Here, the fatty acid profile of Rhodomonas in relation to cell density during cultivation in a tubular PBR is investigated. It is expected that cell density is an important factor in controlling productivity and fatty acid content of the microalgae because cell density is important in determining light availability due to the self‐shading of the algae. The carbon productivity as a function of cell density is described by a saturation curve. The carbon productivity and the productivity of total fatty acids are lowest at the lowest cell density, and independent of cell density at higher cell densities. The relative contribution of the two poly‐unsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increases with increasing cell density and saturates at 1 × 10⁶ cells/ml. We conclude that large‐scale production of Rhodomonas in this tubular PBR should take place at cell densities of 1 × 10⁶ cells/ml, while there are indications for increasing difficulties in maintaining steady‐state production in this PBR at higher cell densities.  相似文献   

Development of Nondestructive Screening Methods for Single Kernel Characterization of Wheat     

Jesper Pram Nielsen  Dorthe Kjr Pedersen  Lars Munck 《Cereal Chemistry》2003,80(3):274-280

The development of nondestructive screening methods for single seed protein, vitreousness, density, and hardness index has been studied for single kernels of European wheat. A single kernel procedure was applied involving, image analysis, near‐infrared transmittance (NIT) spectroscopy, laboratory density determination, single kernel characterization system (SKCS), and finally Kjeldahl protein determination on the crushed single kernels. Single kernel NIT spectroscopy showed excellent ability to determine protein content, and some ability for determination of single kernel vitreousness. Nondestructive determination of single kernel density, either based on NIT spectroscopy or based on image analysis and kernel weight, needs to be further improved for practical use. The use of SKCS hardness index as a true single kernel hardness reference in a NIT prediction model resulted in a poor predictability. However, by applying an averaging approach, in which single seed replicate measurements are mathematically simulated, a very good NIT prediction model was achieved. This suggests that the single seed NIT spectra contain hardness information, but that a single seed hardness method with higher accuracy is needed to achieve a good NIT prediction model for single kernel hardness.  相似文献   

Reconstructing historical trends of small pelagic fish in the Java Sea using standardized commercial trip based catch per unit of effort     

Massimiliano Cardinale  Duto Nugroho  Lars Hernroth 《Fisheries Research》2009,99(3):151-158

Pelagic fish stocks in the Java Sea have been exploited intensively since the beginning of the 1970s. However, due to the effect of increased fishing power of the fleets and the changing nature of spatial and temporal distribution of the fishing effort, assessment of stock trends based on commercial data of catch and effort requires the standardization of both effort and catch data. Here we present the first attempt to reconstruct a standardized time series of commercial catch per unit of effort (CPUE) for the main pelagic species exploited by the purse seine fleet in the Java Sea. The results showed that all the stocks analysed have largely declined since the beginning of the 1990s. For bigeye scad, Indian mackerel and sardine, current estimates are only between 3 and 19% of the maximum observed value while round scads and spotted sardine biomass estimates lie between 18 and 34%. However, our assumptions about the effect of lamp power and level of creeping and the fact that the influence of fish density on catchability and the effect of targeting were not taken into account thus observed decline is a rather conservative estimate of the real decline of the stocks. If effective management actions are not put in place as a matter of urgency in the Java Sea for small pelagic fisheries, one runs the risk of adding those species to the long list of overexploited stocks of the world oceans.  相似文献   

Repeated sublethal freshwater exposures reduce the amoebic gill disease parasite,Neoparamoeba perurans,on Atlantic salmon          下载免费PDF全文

Daniel William Wright  Barbara Nowak  Frode Oppedal  Phil Crosbie  Lars Helge Stien  Tim Dempster 《Journal of fish diseases》2018,41(9):1403-1410

Freshwater bathing is one of the main treatment options available against amoebic gill disease (AGD) affecting multiple fish hosts in mariculture systems. Prevailing freshwater treatments are designed to be long enough to kill Neoparamoeba perurans, the ectoparasite causing AGD, which may select for freshwater tolerance. Here, we tested whether using shorter, sublethal freshwater treatment durations are a viable alternative to lethal ones for N. perurans (2–4 hr). Under in vitro conditions, gill‐isolated N. perurans attached to plastic substrate in sea water lifted off after ≥2 min in freshwater, but survival was not impacted until 60 min. In an in vivo experiment, AGD‐affected Atlantic salmon Salmo salar subjected daily to 30 min (sublethal to N. perurans) and 120 min (lethal to N. perurans) freshwater treatments for 6 days consistently reduced N. perurans cell numbers on gills (based on qPCR analysis) compared to daily 3 min freshwater or seawater treatments for 6 days. Our results suggest that targeting cell detachment rather than cell death with repeated freshwater treatments of shorter duration than typical baths could be used in AGD management. However, the consequences of modifying the intensity of freshwater treatment regimes on freshwater tolerance evolution in N. perurans populations require careful consideration.  相似文献