Effects of environmental stress on forest crown condition in Europe. Part II: Estimation of stress induced by meteorology and air pollutants

In order to assess the relationship betweenenvironmental stress and crown condition of foresttrees monitored since 1986 in Europe, estimates ofstress factors, including temperature stress, droughtstress and air pollution stress, were derived with thebest data, methods and models currently available.This paper presents information on the methods used toderive such stress factors, and on the overall ranges,the temporal trends, the spatial distribution and thereliability of the calculated stress factors. Thetemperature stress indices did not show much temporalvariation between 1985 to 1995. As expected spatialpatterns were north-south orientated, going fromcolder northern regions to warmer southern regions.The calculated relative transpiration showed a morecomplex pattern, coinciding to a large extend withpatterns of rainfall and temperature. Potential aciddeposition decreased between 1986 and 1992, butremained fairly constant after 1992. The strongdecrease was mainly the result of the decrease inSO_x deposition, and to a small decrease inNO_y deposition. Highest levels of the S and Ndeposition were calculated in Central and WesternEurope. Base cation deposition was largest in coastalareas and in southern Europe. This is mainly due tosoil dust, Sahara dust and sea salt. Base cationdeposition can compensate almost entirely for thepotential inputs in the south of Europe, whereas incentral Europe it equalled about 25% of thepotential acid input. A comparison between sitespecific modelled deposition and deposition derivedfrom throughfall data showed that the total aciddeposition is usually overestimated by the model,whereas the total nitrogen deposition isunderestimated, especially at plots with high nitrogenloads. There is, however, a significant correlationbetween measured and modelled data for all S and Ndeposition, thus allowing their use in a statistical analyses.     

Comparison of microsatellite and SNP DNA markers for pedigree assignment in Black Tiger shrimp,Penaeus monodon

Custom‐built single‐nucleotide‐polymorphism (SNP) marker systems that are compatible with Sequenom^® chemistry are compared with a general purpose microsatellite marker system in their ability to accurately assign Black Tiger shrimp parentage. The microsatellite system consisted of 13 markers, while the SNP systems comprised of 63 (SNPa), 59 (SNPb) or 122 markers (SNPab). Comparisons were made using animals from commercial breeding lines with thresholds for assignment derived using simulated genotypes. Pedigree assignment for commercial lines was highest when panel SNPab was used. Panel SNPa, panel SNPb and Msat functioned with an overall similar level of power for pedigree assignment, however, for some families, the Msat panel was not as powerful. Pedigree assignment for the simulated diploid genotypes was higher for all SNP panels compared with Msat. Overall the three SNP panels provided parentage assignment rates suitable for commercial shrimp breeding programs with assignment rates in the simulated genotypes greater than 96.8% and correct assignments greater than 99.3%. Compared with the microsatellite panel, custom‐built SNP panels, whether they operate as single panels, or as a combined panel, have improved power to perform dam and sire assignment to progeny and provide faster turnaround time as they are compatible with Sequenom^® chemistry.     

Population variation in traits of Deladenus siricidicola that could influence the biocontrol of Sirex noctilio in South Africa

Deladenus siricidicola is the primary biocontrol agent of the invasive woodwasp, Sirex noctilio. The nematode is mass-reared in culture on the S. noctilio symbiotic fungus, A. areolatum, but can also be induced to convert into its infective form in culture. The aim of this study was to explore the level of variation among a collection of D. siricidicola strains to convert into the infective form in culture. In addition, we measured variation in growth of the nematode on a strain of A. areolatum that is commonly used for laboratory rearing. Both traits could influence laboratory rearing and efficiency in the field. The 22 strains from three countries showed significant variation in the frequency of conversion into the infective form in culture. Even genetically uniform strains from South Africa displayed a range of variation in this trait. There was also significant variation in the growth of D. siricidicola on A. areolatum. These results emphasise the importance of considering variation in traits in D. siricidicola that could influence a biological control program. They also provide tools that could be used to screen larger collections of D. siricidicola for variation in traits linked to virulence and reproduction.