Comparison of mobile and stationary spore-sampling techniques for estimating virulence frequencies in aerial barley powdery mildew populations

Gene frequencies in samples of aerial populations of barley powdery mildew ( Erysiphe graminis f.sp. hordei ), which were collected in adjacent barley areas and in successive periods of time, were compared using mobile and stationary sampling techniques. Stationary samples were collected from trap plants in three periods within 1 week at a distance of more than 1000 m from the nearest barley field. At four dates within the same 8-day period, other samples were collected by a mobile spore trap along four sampling routes of a total distance of 130 km around the stationary stand of exposure. The samples were characterized by virulence genotypes defined according to infection types on 12 near-isogenic barley lines, and frequencies of single virulence genes were subsequently calculated. The three samples collected at the stationary site differed significantly with respect to allele frequencies at three loci. The main wind direction was different in the three sampling periods, implying different powdery mildew sources. For the mobile exposure, the differences between routes were not significant for any locus. However, the routes differed most for the loci under direct selection by host resistances genes, indicating a different distribution of source varieties along routes. There was no difference between allele frequencies at different dates, indicating that the proportions of spores from different source varieties were similar at these dates. In conclusion, samples collected by the stationary technique will mainly reflect the source varieties present in the local area, whereas samples collected by the mobile spore trap will mainly reflect sources close to the sampling route. Therefore, sampling sites as well as sampling routes should be defined such that source varieties are representative for the overall varietal distribution in the survey region considered.     

Changes in the glucosinolate content of oilseed rape plants following infection with turnip mosaic virus

Low and high glucosinolate cultivars of oilseed rape were analysed for variation in both individual and total glucosinolate content up to 27 days after inoculation with turnip mosaic virus. Both infected and control plants of the two cultivars differed in the concentration of aliphatic, aromatic and indole glucosinolates. The biggest differences in glucosinolate content between the cultivars were found in the aliphatic and aromatic glucosinolate groups. Infected plants of the high glucosinolate cultivar, Solida, possessed lower amounts of glucosinolates, than did healthy control plants. Similar results were obtained with a low glucosinolate cultivar, S1. No significant difference was found between the two cultivars in resistance to turnip mosaic virus, using qualitative and quantitative ELISA to determine virus content in their tissues.     

Canine Idiopathic Thrombocytopenic Purpura

Canine idiopathic thrombocytopenic purpura (ITP) is a disease in which antibodies bound to the surface of platelets mediate premature platelet destruction by macrophages. ITP in dogs and chronic ITP in humans are analogous diseases. This article draws on information from the literature on ITP in dogs and in humans, and reviews the pathogenesis, diagnosis, and treatment of ITP in dogs. J Vet Intern Med 1996;207–218. Copyright © 1996 by the American College of Veterinary Internal Medicine .     

Amino acid interactions in chick nutrition. 3. Interdependence in amino acid requirements

The quantitative nature of specific interactions between certain indispensable amino acids has been examined in a series of factorial experiments with young chicks.

It was demonstrated that when the dietary concentration of lysine was 1.10 per cent, the arginine requirement of the chick was 0.80 per cent. When the lysine concentration was raised to 1.35, 1.60 or 1.85 per cent of the diet, the arginine requirement was increased to 0.92, 1.04 and 1.15 per cent of the diet respectively. In another experiment, it was found that when due importance had been attached to the interaction between lysine and arginine, the requirements for these amino acids could be lowered to 0.94 per cent and 0.81 per cent respectively. These concentrations are considerably lower than those normally recommended for young chicks.

The interrelationship between leucine and isoleucine has also been defined in quantitative terms. At concentrations of 1.40, 2.15 or 2.90 per cent leucine, the isoleucine requirement was 0.58, 0.62 and 0.65 per cent of the diet respectively.

In a further study, a similar dependence of valine requirements upon the dietary concentration of leucine was observed: at concentrations of 1.40, 2.40 or 3.40 per cent leucine, the valine requirement was shown to be 0.77, 0.89 and 1.01 per cent respectively. The results of the experiment on the threonine‐tryptophan interaction indicated that at concentrations of 0.80, 1.30, 1.80 or 2.30 per cent threonine, the tryptophan requirement was 0.17, 0.18, 0.19 and 0.20 per cent of the diet respectively.

The results of the present study permit the general conclusion that the requirements of amino acids are interdependent.     

Photorefractoriness in broiler breeders: sexual maturity and egg production evidence

1. Photorefractoriness was assessed in two lines of broiler breeders. In one trial, male-line and female-line pullets were reared on the floor and transferred to individual cages at 15 weeks. Birds were either maintained on 8-, 11- or 16-h photoperiods or transferred from 8- to 16-h photoperiods at 67 or 124 d. In the second trial, female-line pullets were concurrently housed in the same rearing facilities as trial 1 and transferred to adult floor-pens at 12 weeks. These birds were either maintained on 11- or 16-h photoperiods or transferred from 8- to 11-h or from 8- to 16-h photoperiods at 140 d. 2. In the cages, male-line and female-line birds responded similarly to the lighting treatments, but with the male-line maturing 1 to 2 weeks later than the female-line in each case. Birds on constant 11-h photoperiods matured 3 to 8 d earlier than constant 8-h birds, but 3 weeks earlier than constant 16-h birds. Birds photostimulated at 67 d matured at a similar time to constant 16-h birds, but almost 7 weeks later than those transferred from 8 to 16 h at 124 d. In the floor facilities, constant 11-h birds matured 3 weeks earlier than constant 16-h birds, but almost 2 weeks later than either of the photostimulated groups. Birds transferred from 8 to 16 h matured 4d earlier than those transferred from 8 to 11 h. 3. Caged birds maintained on 16 h or transferred from 8 to 16 h at 67 d laid at least 24 fewer eggs, and had more hens not laying at 58 weeks, than birds maintained on 11-h days or those transferred from 8 to 16 h at 124 d. In the floor-pens, constant 11-h and both photostimulated groups produced about 20 more eggs to 56 weeks of age than the constant 16-h controls. 4. Collectively, these findings indicate that conventionally managed broiler breeders exhibit photorefractoriness. Additionally, a combination of photorefractoriness and controlled feeding appears to prevent broiler breeders from being photoresponsive until at least 10 weeks of age, and to cause some individuals still to be photoperiodically non-responsive at 18 weeks.