Inoculation of pines with mycorrhizal fungi in natural soils—III: Effect of soil fumigation on rate of infection and response to inoculum density

Pinus radiata seedlings were inoculated with basidiospores of Rhizopogon roseolas and Suillus granulatus, and with chlamylospores of two unidentified but highly effective mycorrhizal fungi in undisturbed cores of natural soil fumigated with methyl bromide. Fumigation stimulated mycorrhizal infection rate and enhanced the response of seedlings to increasing concentrations of both inoculum types, but the effect of chlamydospore inoculum was more favoured by fumigation than that of basidio-spores. Chlamydospore inocula appear more sensitive to competitive and antagonistic soil microorganisms than basidiospores. Soil fumigation appears a necessary adjunct to the use of chlamydospores as inoculants in nurseries and is discussed in relation to nursery culture of pines.     

In vitro experiments simulating the possible fates of aphid honeydew sugars in soil

In vitro intact soil cores were treated with sugar amendments at a rate equivalent to that of honeydew produced by a population of tree dwelling aphids. The priming action induced by such amendments was dependent upon the soil type, nature of sugar added and degree of repetition of amendment. A hypothesis has been proposed to explain the presence of a positive priming effect in a woodland soil and a negative priming effect in a grassland soil after equivalent sucrose additions.     

Evaluation of techniques for quantitative detection of Phytophthora cinnamomi

Three baiting techniques and a sieving technique were evaluated for the quantitative detection zof Phytophthora cinnamomi Rands. Baiting with seedlings of Lupinus angustifolius L. (blue lupins), cotyledons of Eucalyptus sieberi F. Muell. and pear fruits cv. Packham's Triumph, detected one chlamydospore introduced into 50 g of either sand or soil. Sieving detected one chlamydospore in 50 g sand and also in 5 g soil. In naturally-infested soil, diluted with a similar non-infested soil, P. cinnamomi was detected at dilutions of $\text{1}\text{8}$ and $\text{1}\text{128}$ by the sieving and the baiting techniques, respectively. In general, pears were the most satisfactory bait for the detection and isolation of P. cinnamomi. The potential of baiting techniques for estimating numbers of propagules of P. cinnamomi in naturally-infested soil is discussed.     

Effects of organic amendments on evolution of ethylene and other hydrocarbons from soil

Evolution of C₂H₄ from soils under anaerobic conditions was stimulated by amendment with cereal straw, but hay had little effect. Temporary restoration of aerobic conditions resulted in large increases in C₃ and C₄ hydrocarbons, with both straw and hay amendments. Several known products of the fermentative degradation of carbohydrate increased the evolution of hydrocarbons under anaerobic, and to a greater extent, under aerobic conditions. In particular, ethanol and butyric acid promoted the formation of C₂H₄ and propylene, respectively. The association between degradation products and C₂H₄ suggests that both may be implicated when root growth is adversely affected by the anaerobic decomposition of plant residues.     

Studies on Herpesvirus scophthalmi infection of turbot Scophthalmus maximus (L.): Histopathological observations

Abstract. The histological features of the disease caused by infection of turbot by Herpesvirus scophthalmi are described. Infection of epidermal cells of skin and gill resulted in the formation of giant cells showing a variety of nuclear and cytoplasmic changes associated with the replication of the virus. The effects of the condition together with possible control measures are discussed.     

Conservation of the jackass penguin (Spheniscus demersus (L.))

The jackass penguin Spheniscus demersus (L.) is confined to the coastal waters of southern Africa, and breeds on 18 islands predominantly within the region of the cold, nutrient rich Benguella current. Since the early 1900s the species' population has declined in numbers of unknown magnitude. The decline appears to be continuing, although the absence of reliable census data precludes an accurate measurement of the rate of change. The initial fall in numbers was undoubtedly due to severe disturbance of nesting birds and excessive commercial exploitation of eggs. The average annual egg crop for the period 1900-30 exceeded 450,000 eggs from Dassen Island alone. Egg collection has been suspended temporarily, but the species now appears to be threatened by oil pollution, and by competition with a pelagic shoal fish industry. Threats to breeding colonies are posed by harbour developments. These factors are discussed and evaluated. South African marine organisms are considered officially to be an economic resource and are heavily exploited. Legislation governing the control of this resource is the concern of the Ministry for Economic Affairs. There is no provision for any government body to investigate the status and biology of economically insignificant, but yet integral, components of the marine ecosystem. The major priority of conservations is to safeguard the jackass penguin population at its present level. This includes proclamation of several offshore islands and their surroundings as national nature reserves. We consider current efforts to rescue, clean and rehabilitate oiled seabirds as contributing little to conservation in real terms, even though the activity has an important humanitarian and educational function. Research priorities include a comprehensive census of the jackass penguin and other seabird populations in southern Africa; a study of mortality and recruitment, with particular attention to factors affecting the rates of these processes; a study of the dynamics of the penguin/prey interaction, with special reference to the possible effects of competition with the pelagic fishing industry; an evaluation of the degree of disturbance that nesting penguins can tolerate; an investigation into the temporal and spatial patterns of oil pollution incidents, oil slick occurrence and movement, and the development of methods of keeping birds away from oil slicks; and, lastly, an evaluation of the efficacy of rehabilitating oiled penguins as a contribution to maintaining or increasing the current jackass penguin population. The responsibility for these projects rests with the South African government.     

Current status of two endangered Caribbean rodents

Living rodents of the genus Geocapromys of the hutia family have been known during this century on three Caribbean islands (Walker, 1968). Visits were made in 1974 to Jamaica and Little Swan Island to check the current status of two of these endangered populations. It appears from these field investigations that the Swan Island hutia, Geocapromys brownii thoracatus, has been exterminated from Little Swan Island. The main cause may have been predation by cats introduced in the late 1950s and after. The Jamaican hutia, G. b. brownii, remains in three remote areas of Jamaica. It exists at low population levels which have been much reduced from those occurring 30 years ago. The Jamaican hutias are shy and secretive in habits compared to the undisturbed Bahamian hutias, G. i. ingrahami, of East Plana Cay, Bahama Islands.     

Thermal and spectrophotometric analysis of some fungal melanins and soil humic compounds

Seven types of fungal melanins were compared with humic compounds from chernozem and podzol soils and with commercial humic acid. The results indicate some similarities but also distinct differences between the melanins and humic substances in spectral characteristics in the UV and visible regions and in their resistance to thermal degradation.