Further properties of black raspberry latent virus, and evidence for its relationship to tobacco streak virus

Purified preparations of an isolate of black raspberry latent virus (BRLV) contained quasispherical particles with a mean diameter of 28·5 nm; these particles were resolved into three sedimenting components (s_{20, w}= 82S, 95S and 104S), but when centrifuged to equilibrium in caesium chloride solution they formed a single infective band (σ= 1·35 g/cm³). During electrophoresis in polyacrylamide gels, virus particles separated into three classes, and virus RNA was resolved into three major (mol. wt 1·35, 1·10 and 0·85 × 10⁶) and one minor (mol. wt 0·4 × 10⁶) component. The protein from virus particles had an estimated mol. wt of 28000. Isolates of BRLV were found to be serologically related but not identical to some strains of tobacco streak virus. No symptoms developed in black raspberry seedlings infected with BRLV by mechanical inoculation, nor in eight red raspberry cultivars infected by graft inoculation. However, graft inoculation of BRLV to Rubus henryi, R. phoenicolasius and Himalaya blackberry induced symptoms typical of necrotic shock disease.     

The use of supplementary foods by Australian magpies Gymnorhina tibicen: Implications for wildlife feeding in suburban environments

Abstract The provision of foods to wild birds is an extremely common practice among householders throughout the Western world. Nonetheless, concerns over potential impacts of the practice are currently being raised, including the possibility that some species may become reliant on human‐provided food. We compared the foraging and breeding ecology of pairs of fed and unfed Australian magpies Gymnorhina tibicen living in suburban environments in Brisbane, Queensland, Australia. Detailed behavioural observations of both foraging and chick provisioning were made for males and females of both groups throughout the breeding season. Natural foods dominated the diets of both fed and unfed magpies, making up 76% and 92% of all items consumed respectively. During the morning, fed magpies obtained fewer food items during ground foraging than did unfed birds, apparently because they visited suburban feeding stations more often during the early part of the day. At other times, the amount of food items obtained during foraging was similar for both fed and unfed birds. Magpies utilizing suburban feeding stations started all breeding activities significantly earlier than unfed magpies, except during the fledgling phase. Both fed and unfed magpie parents provisioned their chicks predominantly with natural food. Magpies were not reliant or dependent on supplementary food provided by wildlife feeders at any time during the breeding season. Although many magpies did utilize suburban feeding stations extensively, they continued to forage for and provision their chicks with natural food.     

SLUG FEEDING BEHAVIOUR IN RELATION TO CONTROL WITH MOLLUSCICIDAL BAITS

The feeding behaviour of Deroceras reticulatam (Müller)presented with molluscicidal baits in laboratory and terrariatrials is described and discussed in relation to pest slug control.Both metaldehyde and Methiocarb appears to be more effectivein wet conditions and less repellent to slugs allowing moreactive ingredient to be consumed before termination of feeding (Received 16 November 1987; accepted 15 February 1988)     

The Effects of Moisture on Acetylene Reduction by Mats of Blue-green Algae in Sub-tropical Grassland

During the dry winter months desiccation is the main factorpreventing nitrogen fixation by mats of blue-green algae inkikuyu lawns. In the wetter summer months a few days of sunshinewithout rain will dry out the algal mats and depress nitrogenfixation unless the algae are protected by swards of grass.Dry mats resume nitrogen fixation within an hour of becomingdamp and attain their normal rate of fixation within 5 h. Maximumfixation rates occur at 100 per cent relative humidity and withsoil moisture contents of 22 to 42 per cent. Dry algal matsare unable to take up sufficient water as vapour (even in saturatingconditions) to permit resumption of acetylene reduction. Algal-dominatedsoils show greater water retention than adjacent bare soils.     

The fecundity of dace, Leuciscus leuciscus (L.) in Emral Brook, Clwyd, North Wales

SUMMARY. Estimates of the fecundity of dace were made on 105 mature females using the dry method of Simpson (1959). The reliability of the counting procedure was assessed and found to be satisfactory. Fecundity was examined in relation to fork length (cm), somatic weight (g), ovary weight (g) and age (years). Logarithmic multiple regressions of fecundity on these variables showed that neither log fork length nor log somatic weight contributed significantly towards explaining the observed variations in fecundity. The best prediction equation for fecundity, incorporated both log ovary weight and log age. Incidents of extensive follicular atresia were found in the ovaries of 19% of the female dace examined and the frequency of occurrence of this phenomenon increased with age.     

Differential Transport of Boron in Tomato (Lycopersicon esculenlum Mill.)

Two tomato cultivars, T3238 (B-inefficient) and Rutgers (B-efficient), were grown in solution cultures with increasing concentrations of B. Rutgers was about 15 times more efficient than T3238 in utilizing the B in the growth medium. Rutgers translocated more B to top leaves than the inefficient T3238. When plants developed B-deficiency symptoms, there was no evidence of B redistribution between tissues. Reciprocal grafts of T3238 and Rutgers demonstrate root control of B transport.     

Effects of powdery mildew at different growth stages on grain yield of barley

Pot-grown barley plants (cv. Proctor) were exposed to infection by powdery mildew during four stages of development, G.S. 2–6, G.S. 7–9, G.S. 10-10-5 and G.S. 11 (Feekes scale, Large, 1954). All combinations were examined (i.e. 2⁴ factorial). The numbers of fertile tillers at harvest were significantly reduced by mildew during periods G.S. 2–6 and G.S. 7–9. Numbers of grains per head and grain size (1000 grain weight) were significantly reduced by mildew only during G.S. 2–6. Effects, on components of yield, of the four mildew treatments were found to be almost entirely additive. The only significant interactions found were for grain size: in this instance there was some interaction between treatments at G.S. 2–6 and G.S. 10-10-5 and between treatments at G.S. 2–6, G.S. 7–9 and G.S. 10-10-5.