Pesquisa | SciELO

Bathycoelia distincta is one of the most dominant stink bug pests associated with macadamia orchards in South Africa. Understanding the toxicity and sublethal effects of insecticides on this pest is essential for its effective management. This study tested four commercial insecticide formulations, consisting of one organophosphate (acephate) and three pyrethroids (lambda-cyhalothrin, beta-cyfluthrin and tau-fluvalinate). The toxicity of these insecticides and their behavioural effects on mobility were assessed. The sublethal effects of lambda-cyhalothrin on the biological parameters of parent B. distincta (F0) and offspring generations (F1) were also determined by treating B. distincta adults with sublethal concentrations (LC10 and LC30). In toxicity bioassays, acephate was more toxic to B. distincta than lambda-cyhalothrin, beta-cyfluthrin and tau-fluvalinate. Behavioural changes were only observed in bugs exposed to pyrethroids, resulting in an increase in the distance walked and decrease of angular velocity. In the F0 generation, LC30 reduced the fecundity whereas the LC10 and LC30 accelerated development of the F1 generation. These results suggest that pyrethroids may enhance the dispersal of this pest and stimulate the growth of offspring populations. Further experiments should be conducted to confirm these results and understand the mechanism of action of pyrethroids on B. distincta.

Some of the most significant breakthroughs in the biological sciences this century will emerge from the development of next generation sequencing technologies. The ease of availability of DNA sequence made possible through these new technologies has given researchers opportunities to study organisms in a manner that was not possible with Sanger sequencing. Scientists will, therefore, need to embrace genomics, as well as develop and nurture the human capacity to sequence genomes and utilise the 'tsunami' of data that emerge from genome sequencing. In response to these challenges, we sequenced the genome of Fusarium circinatum, a fungal pathogen of pine that causes pitch canker, a disease of great concern to the South African forestry industry. The sequencing work was conducted in South Africa, making F. circinatum the first eukaryotic organism for which the complete genome has been sequenced locally. Here we report on the process that was followed to sequence, assemble and perform a preliminary characterisation of the genome. Furthermore, details of the computer annotation and manual curation of this genome are presented. The F. circinatum genome was found to be nearly 44 million bases in size, which is similar to that of four other Fusarium genomes that have been sequenced elsewhere. The genome contains just over 15 000 open reading frames, which is less than that of the related species, Fusarium oxysporum, but more than that for Fusarium verticillioides. Amongst the various putative gene clusters identified in F. circinatum, those encoding the secondary metabolites fumosin and fusarin appeared to harbour evidence of gene translocation. It is anticipated that similar comparisons of other loci will provide insights into the genetic basis for pathogenicity of the pitch canker pathogen. Perhaps more importantly, this project has engaged a relatively large group of scientists including students in a significant genome project that is certain to provide a platform for growth in this important area of research in the future.

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