Effect of drought stress on content and composition of seed alkaloids in narrow-leafed lupin, Lupinus angustifolius L.

The effect of drought stress at three growth stages on seed alkaloid content in two sweet (W26 and Polonez) and one bitter variety (Zubr) of spring sown Lupinus angustifolius L. was investigated in a lysimeter experiment on sandy soil in Denmark. Full irrigation resulted in medium alkaloid content. Drought stress during the vegetative phase increased alkaloid content to 0.094, 0.192 and 2.55% of seed dry matter, respectively. At the flowering stage alkaloid content decreased to 0.070, 0.152 and 1.99%, while drought stress during pod-filling increased alkaloid content for the determinate variety W26 to 0.097%, but decreased it to 0.161 and 1.98% for the two indeterminate varieties Polonez and Zubr, respectively. Drought during either flowering or pod-filling resulted in an increased mean seed weight and a reduced number of seed per square metre. Alkaloid content was negatively correlated to seed weight. The alkaloid composition differed for the three genotypes, and was affected by drought treatment. Compared to the bitter variety the sweet varieties were characterized by reduced concentrations of lupanin, 13-hydroxylupanin and angustifolin, whereas spartein, isolupanin and isoangustifolin were little affected.     

Observed and predicted changes over eight years in frequency of barley powdery mildew avirulent to spring barley in France and Denmark

Aerial populations of Blumeria graminis f.sp. hordei were studied in two French and two Danish regions from 1991 to 1999, at a time of year when only winter barley was present. A high frequency of genotypes not able to grow on the spring-sown crop of the previous growing season (denoted 'spring-avirulent') was observed in most years and regions. This frequency increased with increasing proportion of winter barley; it was highest in France and decreased in general over the 8-year period. Most of the spring-avirulent genotypes possessed the V _{a 22} virulence gene, matching a resistance that has never been present in barley cultivars grown in Europe. A hypothetical cropping system, including winter- and spring-sown crops with three resistance genes altogether, was constructed to mimic the utilization of host cultivars in the four regions. Results from a mathematical model simulating changes in the composition of the pathogen population in this system, demonstrated that selection solely due to host resistance genes, i.e. without assuming any cost of virulence, might lead to such results as those observed. The changes in frequency of spring-avirulent genotypes and the frequency of unnecessary virulence genes may be predicted from the proportion of the barley area sown with winter barley, the use of resistance genes in the cultivars, the initial composition of the pathogen population, and hitch-hiking due to gametic disequilibria.     

Nematode migration and nutrient diffusion between vetch and barley material in soil

This paper deals with migration of nematodes along nutrient gradients in soil. Portions of barley straw and green vetch leaves were mixed with soil and buried at 6, 12, 18, and 50 mm distance from each other in soil. During the following 12 weeks respiration activity, microbial (SIR) biomass, nitrogen limitation of respiration activity in soil slurries all indicated that nitrogen was transferred in the soil from the nutrient rich vetch to the nutrient poor barley at least during the first 3 weeks of the experiment. Twelve out of 39 taxonomic groups of nematodes showed different growth in the two plant material-soil mixtures. Only one of these taxonomic groups (long rhabditid larvae) suggested that migration could have contributed to population development; for three other groups (short rhabditid larvae, Aphelenchoides, and Bursilla) nutrient transport through the soil was the likely mechanism for a distance-dependant population development. We suggest that for most microbivorous nematodes, except larvae of fast growing bacterivores, migration over distances exceeding one centimetre does not contribute markedly to population development even when cues such as nutrient gradients to stimulate the activity exist.     

Escape‐related behaviour of Atlantic cod,Gadus morhua L., in a simulated farm situation

Cultured fish escaping from farms represent an economic loss as well as a potential problem for wild fish populations. This study investigated the escape‐related behaviour of farmed Norwegian coastal and northeast Arctic cod (NEAC), Gadus morhua L. Six groups of fish were observed during three replicate trials in a large tank that was split into two equal parts by a net wall. The fish could move freely through an opening in the net during the trials. Three groups were not fed during the trials. The first escape occurred shortly after producing the net opening (11±10.5 min; mean±standard deviation). Norwegian coastal cod were more prone to escape than the NEAC. A starvation period of 9 days increased the number of fish on the escape side of the tank. Net biting and net inspection by the fish were frequently observed, irrespective of whether the fish were fed or not. The same fish were repeatedly found on the escape side of the tank, but the propensity for recurrent escape behaviour was not related to genotype, feeding status or size. The results suggest that other factors, such as individual variation in boldness or exploration behaviour, could affect the willingness to escape.     

Application of anti-BCG antibody for rapid immunohistochemical detection of bacteria, fungi and protozoa in formalin-fixed paraffin-embedded tissue samples

The applicability of an anti-Mycobacterium bovis (BCG) antibody-based immunohistochemistry (IHC) procedure was investigated using everyday veterinary pathological samples collected from 13 different animal species. Fifty-one formalin-fixed and paraffin-embedded tissue samples were selected for this study. Forty, 4 and 7 tissue samples contained different species of bacteria, fungi and protozoa, respectively. Three serial sections were prepared in each case. Two sections were pre-treated with enzyme and heat, respectively, while the last section was not pre-treated. In seven cases the sensitivity of histochemical staining (HSM), IHC and bacteriological culture were compared. Heating of the sections in a microwave oven was the most effective method in the case of almost all pathogens used. Strong or moderate positive reactions were observed for 26 bacterial species, all fungal and 2 protozoal species, while weak reactions occurred for 2 bacterial and 1 protozoal species. Only 4 protozoal and 12 bacterial species, including Leptospira and all the five Mycoplasma species examined, showed no reaction in this test. IHC had almost the same sensitivity as bacteriological culture and was more sensitive than HSM. The IHC method presented here should be preferred to HSM as a general screening tool in cases where pathological lesions suspicious for infections are evident and no microorganism can be cultured in vitro or only formalin-fixed tissue samples are available for the laboratory examination.