Action of natural phytosanitary products on Bacillus thuringiensis subsp. kurstaki S-1905.

The objective of this study was to evaluate the effects of natural phytosanitary products (NPs) on spores and crystals of Bacillus thuringiensis subsp. kurstaki S-1905 (Btk S-1905). For the spore assay, NPs and bacteria were applied in combination and individually. For the combined application, Btk S-1905 + NP mixtures were inoculated on nutrient agar (NA), and for the separate applications, the NPs were spread on NA plates, which were later inoculated with the pathogen. The number of colony-forming units (CFU) per milliliter was quantified after 18 h of incubation. For the crystal protein degradation assay, the Btk S-1905 + NP mixtures were added to the diet of Anticarsia gemmatalis (Lepidoptera: Erebidae), and mortality was evaluated at the following time points: 12, 24, 48, and 72 h. Scanning electron microscopy and agarose gel electrophoresis were carried out. Biogermex and Ecolife® reduced the CFU ml-1 in both combined and separate applications. Biogermex, Ecolife®, and Planta Clean were antagonistic to the action of bacterial toxins, and no product affected the morphology or resulted in the degradation of the crystal proteins. The remaining products evaluated did not reduce the CFU ml-1 and had additive effect when combined with the crystal toxin.

Genotoxic evaluation in Oreochromis niloticus (Fish: Characidae) of recombinant spore-crystal complexes Cry1Ia, Cry10Aa and Cry1Ba6 from Bacillus thuringiensis.

Bioinsecticides from Bacillus thuringiensis (Bt) are widely used around the world in biological control against larval stages of many insect species. Bt has been considered a biopesticide that is highly specific to different orders of insects, non-polluting and harmless to humans and other vertebrates, thus becoming a viable alternative for combating agricultural pests and insect vectors of diseases. The family of Bt δ-endotoxins are crystal-protein inclusions showing toxicity to insects' midgut, causing cell lysis leading to starvation, septicemia and death. The aim of this study is to evaluate the genotoxic potential of recombinant Bt spore-crystals expressing Cry1Ia, Cry10Aa and Cry1Ba6 on peripheral erythrocyte cells of Oreochromis niloticus, through comet assay, micronucleus (MN) test and nuclear abnormalities (NA) analysis. Fish (n = 10/group) were exposed for 96 h at 10(7) spores 30 l(-1), 10(8) spores 30 l(-1) or 10(9) spores 30 l(-1) of Bt spore-crystals. Cry1Ia showed a significant increase in comet cells at levels 1 and 2, but not at levels 3 and 4, so it was not mutagenic nor did it induce MN or NA. These three spore-crystals showed some fish toxicity at only the highest exposure level, which normally does not occur in the field.

Recombinant Cry1Ia protein is highly toxic to cotton boll weevil (Anthonomus grandis Boheman) and fall armyworm (Spodoptera frugiperda).

AIMS: To evaluate the activity of cry1Ia gene against cotton pests, Spodoptera frugiperda and Anthonomus grandis. METHODS AND RESULTS: Had isolated and characterized a toxin gene from the Bacillus thuringiensis S1451 strain which have been previously shown to be toxic to S. frugiperda and A. grandis. The toxin gene (cry1Ia) was amplified by PCR, sequenced, and cloned into the genome of a baculovirus. The Cry1Ia protein was expressed in baculovirus infected insect cells, producing protein inclusions in infected cells. The Cry1Ia protein has used in bioassays against to S. frugiperda and A. grandis. CONCLUSIONS: Bioassays using the purified recombinant protein showed high toxicity to S. frugiperda and A. grandis larvae. Molecular modelling of the Cry1Ia protein translated from the DNA sequence obtained in this work, showed that this protein possibly posses a similar structure to the Cry3A protein. Ultrastructural analysis of midgut cells from A. grandis incubated with the Cry1Ia toxin, showed loss of microvilli integrity. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicate that the cry1Ia is a good candidate for the construction of transgenic plants resistant to these important cotton pests.

Biology of Diadegma sp. (Hymenoptera: Ichneumonidae), a parasitoid of Plutella xylostella (L. ) (Lepidoptera: Yponomeutidae), from Reunion Island / Biologia de Diadegma sp. (Hymenoptera: Ichneumonidae), um parasitóide de Plutella xylostella (L. ) (Lepidoptera: Yponomeutidae), da Ilha Reunião

O gênero Diadegma compreende espécies capazes de parasitar larvas de Plutella xylostella (L.) (DBM). Foram realizados estudos de laboratório com uma população de Diadegma sp. oriunda da Ilha da Reunião, para determinar sua capacidade de parasitismo e a influência da temperatura na sua fecundidade, longevidade, oviposição e o consumo foliar de larvas parasitadas de DBM. A taxa de parasitismo foi de 70 por cento de larvas de segundo e terceiro estádios e 53 por cento de quarto estádio. A 15°C, não houve parasitismo. A 20°C e 25°C, a porcentagem de parasitismo foi próxima a 70 por cento. A 29°C, a porcentagem de parasitismo foi similar (70 por cento), mas houve maior produção de machos. Larvas parasitadas de DBM consomem 35 por cento menos superfície foliar do que larvas não parasitadas. Essa espécie de Diadegma é um possível candidato para ser introduzido em áreas tropicais, onde nenhuma espécie adaptada é conhecida, e onde pode ser usada como complemento às aplicações de Bacillus thuringiensis.

The genus Diadegma have some species able to parasite Plutella xylostella (L.) (DBM). Laboratory studies were carried out on a Diadegma sp. from Reunion Island to elucidate its ability to parasite DBM larvae, and to determine the influence of the temperature on its fecundity, longevity, oviposition and the consumption of cabbage leaves by parasitized DBM larvae. Parasitism rates were close to 70 percent for the L2 and L3 instar, and 53 percent for the L4. At 15°C, there were no progeny. At 20°C and 25°C, the percentage of parasitism was near 70 percent. At 29°C, the percentage parasitism was similar but the number of males produced was higher. Parasitized DBM larvae consumed 35 percent less leaf surface than non parasitized larvae. This Diadegma sp. is a possible candidate for introduction into tropical areas, where no tropically adapted Diadegma species are known and could complement Bacillus thuringiensis treated systems.