A CAPS marker derived from tomato 12-oxophytodienoate reductase shows putative co-segregation with potato late blight resistance

The jasmonic acid (JA) pathway is involved in the defense mechanisms induced in plants on pathogen attack and the enzyme 12-oxophytodienoate reductase (OPR3) catalyses one of the final steps of JA synthesis. A CAPS marker, OprDM, has been developed using primers designed from the tomato (Solanum lycopersicum)OPR3 cDNA sequence. Sequencing verified that the sequence of the marker derived from potato (Solanum tuberosum) genomic DNA was 98% identical to the corresponding section of that from tomatoOPR3 cDNA. The marker was mapped and examined for association with QTLs for resistance to foliage late blight in potato. OprDM mapped close to marker GP121 on chromosome VII ofS. tuberosum. No marker sequence or clone forOPR3 has previously been mapped in potato or tomato. Results indicated the presence of two putative QTLs for foliage resistance on chromosome VII close to OprDM and CP56. The marker primers could be useful in other studies involving enzymes of the JA synthesis pathway in polymorphicSolanum populations.     

Immunological studies on Vibrio anguillarum

Nineteen strains of Vibrio anguillarum were examined by means of several immunological methods. Nine other strains belonging to the genera Vibrio, Aeromonas and Pseudomonas were also examined for comparison.Lipopolysaccharides were prepared from seven of the V. anguillarum strains. The lipopolysaccharides seem to be species-specific for V. anguillarum, not being detected in any of the other strains examined. Common antigens are also found in V. anguillarum and other species of marine bacteria.The strains of V. anguillarum fall into three different serological groups according to the type of lipopolysaccharide in the cell wall. One of the groups comprises only one strain, this strain being the only one not isolated from diseased fish.The lipopolysaccharides were used in an indirect haemagglutination test. Inhibition of this haemagglutination with tissue extracts from diseased fish can be used for practical purposes in the diagnosis of vibriosis.     

Anesthesia during Vaccination of Atlantic Salmon: Compliance with Recommended Procedures

The preparation and use of two anesthetic agents for fish, a buffered metacaine solution for anesthesia in connection with vaccination procedure, and an available benzocaine solution for minor procedures, were studied at a commercial fish farm producing Atlantic salmon, Salmo salar L., smolts. The procedures were compared with the given recommendations to evaluate compliance with recommended procedures and labels. The personnel were evaluated to be non‐compliant with labels and procedures for both anesthetic agents used and the recommended exposure time in the baths. Five important themes were identified: the preparation and use of the anesthetics, fish welfare, training procedures, and occupational hazard aspects. One important reason for non‐compliance was that the rate of delivery of anesthetized fish to the vaccination table was more dependent on the speed of vaccination, and less on the anesthetic depth of the fish. This may be a management issue. Management decisions may create an environment leading to situations where errors are more likely to occur. Better communication between the fish health‐service team and the personnel, more tailored procedures, and a preprepared anesthetic agent might increase compliance with procedures and may promote fish welfare and welfare of the employees.     

Can timing of spawning explain the increase in egg size with female size in salmonid fish?

A common observation is that egg size increases with maternal size within populations. Several hypotheses have been proposed to explain this phenomenon. Most recently, it was suggested that the optimal egg size depends on female size due to correlations between (i) breeding time and egg size selection and (ii) female size and breeding time, and as such, the positive egg size–maternal size relationship represents an adaptive strategy. Here, we test the second of these two premises in two salmonid species, Atlantic salmon (Salmo salar) and coho salmon (Oncorhynchus kisutch) for which we have detailed breeding and egg size data. The body size of spawning females decreased throughout the season in coho salmon, but not in Atlantic salmon. Furthermore, we did not find a direct correlation between egg size and breeding time, which would also be expected if this premise was correct. Accordingly, breeding date does not appear to be as important as other factors in shaping among female differences in egg size.     

Studies of Didymella bryoniae: The influence of nutrition and cultural practices on the occurrence of stem lesions and internal and external fruit rot on different cultivars of cucumber

Cucumber plants of different cultivars grown under various levels of nutrient supply, climatic conditions and different pruning practices were inoculated withDidymella bryoniae (Auersw.) Rehm. Increased concentration of the nutrient solution in the rockwool, slabs leading to a higher amount of dry matter content in the plant tissue resulted in a lower percentage of internal and external fruit rot in the cultivars Daleva and LD 290/82 (Dæhnfeldt), and in lower percentage of internal fruit rot in cv. Aminex, whereas the effect on cv. Dalibor was insignificant. Differences between cultivars were observed, cv. Dalibor showing the highest level of resistance against internal fruit rot and lowest incidence of nodal and internodal lesions. Separate factors appear to affect the establishment of the pathogen in the nodal tissue and its invasion of the internodal tissue. By raising the temperature to daytime level 3 h before sunrise, the risk of extended periods with high humidity was limited and the incidence of internal fruit rot was reduced. An increased incidence of nodal and internodal lesions and external fruit rot was observed at reduced pruning, leaving wilted leaves and shoots on the plants.     

Tailoring of Atlantic salmon (Salmo salar L.) flesh lipid composition and sensory quality by replacing fish oil with a vegetable oil blend

Atlantic salmon (Salmo salar L.) juveniles were fed either 100% fish oil (FO), 75% vegetable oil (VO), or 100% VO throughout their life cycle to harvest weight followed by a finishing diet period when all groups were fed 100% FO. The two experimental VO diets were tested at two different locations (Scotland and Norway) against the same control diet (100% FO). The VO blend was composed of rapeseed oil, palm oil, and linseed oil using capelin oil as a control for fatty acid class compositions. Flesh fatty acid profiles were measured regularly throughout the experiment, with the times of sampling determined by changes in pellet size/lipid content and fish life stage. Growth and mortality rates were not significantly affected by dietary fatty acid compositions throughout the life cycle, except during the seawater winter period in Norway when both growth and protein utilization were increased in salmon fed 100% VO compared to 100% FO. Flesh fatty acid composition was highly influenced by that of the diet, and after the finishing diet period the weekly intake recommendations of very long chain n-3 polyunsaturated fatty acid (VLCn-3 PUFA) for human health were 80 and 56% satisfied by a 200 g meal of 75% VO and 100% VO flesh, respectively. No effect on flesh astaxanthin levels was observed in relation to changing dietary oil sources. Sensory evaluation showed only minor differences between salmon flesh from the dietary groups, although prior to the finishing diet period, flesh from 100% VO had less rancid and marine characteristics and was preferred over flesh from the other dietary groups by a trained taste panel. After the finishing diet period, the levels of typical vegetable oil fatty acids in flesh were reduced, whereas those of VLCn-3 PUFA increased to levels comparable with a 100% FO fed salmon. No differences in any of the sensory characteristics were observed between dietary groups. By blending VOs to provide balanced levels of dietary fatty acids, up to 100% of the fish oil can be replaced by the VO blend without compromising growth or flesh quality. At the same time, 75% of the dietary fish oil can be replaced without compromising flesh VLCn-3 PUFA content, thereby providing a beneficial nutritional profile for human consumption.     

Screening for intrinsic water use efficiency in a potato dihaploid mapping population under progressive drought conditions

A drought screening experiment focusing on intrinsic water use efficiency (WUE_i) was carried out among 132 clones belonging to a dihaploid potato mapping population. The clones were exposed to progressive soil drying during a five-day period in a greenhouse pot experiment. Analysis of the underlying variables was done based on a multivariate data analysis strategy. The strategy successfully divided the clones into WUE_i performance categories. Differences between clonal WUE_i responses were traced back to differences in the net photosynthetic rate. Stomatal conductance (g_s) did not vary significantly between the clones. Leaf abscisic acid (ABA) concentration and leaf water potential were found to reflect known isohydric behaviour for potato, and a non-linear relationship could be established for g_s and leaf ABA concentration across the WUE_i groups. Similarly, a common non-linear relationship between leaf ABA concentration and soil water potential was found. The latter findings suggest that the investigated population did not harbour significant genetic variation as to ABA production as function of soil desiccation level or with respect to the sensitivity of stomatal aperture vis-à-vis leaf ABA concentration and soil water potential.     

Density‐dependent diet composition of juvenile Atlantic salmon (Salmo salar)

Abstract – Decreases in body growth with increasing population density may be caused by reduced prey delivery rate. However, changes in food quality because of an increasing inclusion of suboptimal prey in the diet may also contribute to such effects. Here, we test for density‐dependent diet composition by creating spatial variation in Atlantic salmon young‐of‐the‐year (YOY) density in three replicate streams and obtain detailed information on individual positions (±1 m) and diet. Diet breadth with respect to prey size increased with increasing local density for the two most common prey types (Chironomidae and Ephemeroptera). For the largest prey type (Ephemeroptera), there was also an increase in mean prey size with increasing density, suggesting that YOY salmon preferentially utilise the smaller prey among those available. According to optimal foraging theory, changes in diet with increasing local density are likely to come at an energetic cost and hence may contribute to the commonly observed density‐dependent growth of juvenile salmonids.