The hymenopterous parasites of Nitidulidae

The known information on hymenopterous parasites of Nitidulidae was consolidated in this article. Species of parasites, nitidulid hosts and, where possible, plant host of the nitidulids are provided along with citations to sources of information. Thirty-three species of hymenopterous parasites are recorded in nine different families. Since nomenclature of several of the parasites has changed, it was updated with the assistance of specialists.     

Control and monitoring: control strategies for Plum pox virus in Canada

In 2000, Plum pox virus (PPV) was discovered in Canada in the provinces of Ontario and Nova Scotia. Delimitation surveys were used to define quarantine areas. An eradication strategy was developed based on a threshold value for virus incidence which triggered removal of the entire orchard block. Each year the threshold value is being lowered until reaching a zero tolerance level. Growers are compensated financially for their losses. A two-tiered certification programme was designed to provide clean replacement trees. Initially, growers planted PPV-tested trees as an interim measure until fully virus-tested stock became available. It is hoped that this eradication programme will eliminate PPV from Canada by 2010.     

The coat proteins and putative movement proteins of isolates of Prunus necrotic ringspot virus from different host species and geographic origins are extensively conserved

A complete sequence for the RNA 3 of Prunus necrotic ringspot virus (PNRSV) is described (Genbank Accession U57046). Primers from this sequence were used to amplify both the movement protein and coat protein genes of 3 other isolates of PNRSV originating from different host species and geographic locations. Comparisons of these sequences with those of other published sequences for PNRSV and the closely related apple mosaic virus (ApMV) showed that both the movement proteins and coat proteins of isolates of PNRSV are extensively conserved irrespective of either the original host or the geographic origin. The movement protein and coat protein of ApMV and PNRSV are sufficiently conserved to suggest that these two viruses may have evolved from a common ancestor. The amino acid sequence of the two coat proteins shows areas of similarity and difference that would explain the serological continuum reported to occur among isolates of these two viruses. Nevertheless, the movement protein and coat protein of the two viruses are sufficiently different so that ApMV and PNRSV should be considered to be distinct viruses.     

Welfare assessment in porcine biomedical research – Suggestion for an operational tool

In recent years, increasing interest in using the pig (Sus scrofa) for biomedical research has become evident. Today, the pig is considered an advantageous alternative animal model for various human diseases and conditions. However, even though a considerable amount of biomedical research has been done on pigs, hardly any studies include systematic welfare assessment. Still, it is essential to assess welfare of laboratory pigs, both domestic pig breeds and smaller purpose-bred breeds, as (1) scientific obligations entail responsibility to ensure and document a fair welfare standard for animals used for experimental purposes; and (2) the scientific outcome can be dependent upon the welfare state of the animals. In order to be able to quantify and control laboratory pig welfare, a practical tool is needed. The purpose of the present paper is to provide an overview of the current status of the extent of welfare assessment in pigs used in biomedical research and to suggest a welfare assessment standard for research facilities based on an exposition of ethological considerations relevant for the welfare of pigs in biomedical research. The tools for porcine welfare assessment presented suggest a method for monitoring the welfare status of individual laboratory pigs, intended to relieve the practical scoring of the welfare of individual pigs as well as the interpretation of the findings.     

The periderms of three North American conifers

Summary The anatomy of periderms in three North American conifers are described and compared. The phellems of balsam fir and eastern hemlock consist of tangential bands of thin-walled phellem (TnP) separated by one, or sometimes more, cell layers of thick-walled phellem (TkP). The phellem of white spruce contains tangential bands of TnP and TkP, as well as one to several cell layers of crystalliferous phellem (CP) abaxially adjacent to every TkP zone. The TkP, and to a lesser extent the TnP, are distinctive for each of the three conifers.The terminations of phellem growth cycles in fir and hemlock are delineated by thickened adaxial suberinic walls in the last-formed layer of TnP cells. In spruce, the adaxial suberinic walls of the last-formed layer of CP cells are thickened. TkP marks the geginning of phellem growth cycles in all three conifers.TkP cells are true suberized phellem cells, not phelloids.     

The optimal stability `window': a mechanism underlying decadal fluctuations in North Pacific salmon stocks?

While recent evidence suggests that North Pacific salmon stocks are influenced by decadal variability in atmospheric forcing of the ocean, the actual combination of physical and biological processes that determines this linkage has not been identified. This paper describes a possible scenario in which water column stability is the primary factor by which the physical environment influences phytoplankton production, the basis for production at higher trophic levels. Variation in the strength of the wintertime Aleutian Low pressure area affects water column stabilities, hence primary production, along the entire eastern boundary of the North Pacific. The `optimal stability window' explains the qualitative relationship between fish stocks and the strength of the winter Aleutian Low, as well as the observed out-of-phase variation between northern and southern salmon stocks.     

Soil inoculation method determines the strength of plant–soil interactions

There is increasing evidence that interactions between plants and biotic components of the soil influence plant productivity and plant community composition. Many plant–soil feedback experiments start from inoculating relatively small amounts of natural soil to sterilized bulk soil. These soil inocula may include a variety of size classes of soil biota, each having a different role in the observed soil feedback effects. In order to examine what may be the effect of various size classes of soil biota we compared inoculation with natural field soil sieved through a 1 mm mesh, a soil suspension also sieved through a 1 mm mesh, and a microbial suspension sieved through a 20 μm mesh. We tested these effects for different populations of the same plant species and for different soil origins.Plant biomass was greatest in pots inoculated with the microbial suspension and smallest in pots inoculated with sieved soil, both in the first and second growth phase, and there was no significant population or soil origin effect. Plant-feeding nematodes were almost exclusively found in the sieved soil treatment. We show that processing the soil to obtain a microbial suspension reduces the strength of the soil effect in both the first and second growth phase. We also show that the results obtained with inoculating sieved soil and with a soil suspension are not comparable. In conclusion, when designing plant–soil feedback experiments, it is crucial to consider that soil inoculum preparation can strongly influence the observed soil effect.