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At least 1,135 records · Page 63Linked to original sources
PubMed2003

Transgenic expression of trypsin inhibitor CMe from barley in indica and japonica rice, confers resistance to the rice weevil Sitophilus oryzae.

Indica and japonica rice (Oryza sativa L.) plants were transformed by particle bombardment with the Itr1 gene encoding the barley trypsin inhibitor BTI-CMe, under the control of its own promoter that confers endosperm specificity, and the maize ubiquitin promoter. From 38 independent transgenic lines of indica (breeding line IR58) and 15 of the japonica (cv Senia) selected, 22 and 11, respectively, expressed the barley inhibitor at detectable levels. The transgene was correctly translated as indicated by western blot analysis with a level of expression in R3 seeds up to 0.31% (IR58) and 0.43% (Senia) of the total extracted protein. The functional integrity of BTI-CMe was confirmed by trypsin activity assays in liquid media and by activity staining gels, performed with seed extracts. The significant reduction of the survival rate of the rice weevil (Sitophilus oryzae, Coleoptera: Curculionidae) reared on homozygous transgenic indica and japonica rice seeds expressing the BTI-CMe, compared to non-transformed controls, and the decrease in the trypsin-like activity of insect crude midgut extracts, confirmed the utility of this proteinase inhibitor gene for the control of important storage pests.

Animals↗
PubMed2001

Association of PCR and feeding bioassays as a large-scale method to screen tropical Bacillus thuringiensis isolates for a cry constitution with higher insecticidal effect against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae.

AIMS: To verify whether the presence of any of the cry1C, 1D, 1E and 1F genes could be associated with high toxicity against fall armyworm. METHODS AND RESULTS: A sample of 60 strains from a large collection of tropical Bacillus thuringiensis (B.t.) isolates was subjected to feeding bioassays and gene-specific PCR. Positive amplification of cry-specific fragments, so confirmed by sequencing, revealed that cry1C was ubiquitous and distributed among high and low mortality classes, cry1D was underrepresented and showed no clear association to high toxicity, and cry1F was not detected. The presence of cry1E significantly correlated to high levels of insecticidal activity, as estimated by linear regression analysis. CONCLUSION: The PCR amplification of cry1E-specific fragments alone appears to be sufficient to identify B.t. strains with high mortality levels against tropical armyworm. SIGNIFICANCE AND IMPACT OF THE STUDY: The approach presented is promising as a simple and efficient method for first-tier, marker-assisted screening of environment-specific B.t. germplasm effective in controlling a single target pest.

Animals↗
PubMed1996

Construction of an improved mycoinsecticide overexpressing a toxic protease.

Mycoinsecticides are being used for the control of many insect pests as an environmentally acceptable alternative to chemical insecticides. A key aim of much recent work has been to increase the speed of kill and so improve commercial efficacy of these biocontrol agents. This might he achieved by adding insecticidal genes to the fungus, an approach considered to have enormous potential for the improvement of biological pesticides. We report here the development of a genetically improved entomopathogenic fungus. Additional copies of the gene encoding a regulated cuticle-degrading protease (Pr1) from Metarhizium anisopliae were inserted into the genome of M. anisopliae such that Pr1 was constitutively overproduced in the hemolymph of Manduca sexta, activating the prophenoloxidase system. The combined toxic effects of Pr1 and the reaction products of phenoloxidase caused larvae challenged with the engineered fungus to exhibit a 25% reduction in time of death and reduced food consumption by 40% compared to infections by the wild-type fungus. In addition, infected insects were rapidly melanized, and the resulting cadavers were poor substrates for fungal sporulation. Thus, environmental persistence of the genetically engineered fungus is reduced, thereby providing biological containment.

Amino Acid Sequence↗
PubMed1991

Control of Culex quinquefasciatus in Myanmar (Burma) and India: 1960-1990.

During the past 30 years three major programmes of research have been carried out in Myanmar (Burma) and India on the ecology and control of Culex quinquefasciatus. To differing degrees the programmes have employed environmental, chemical, biological and genetic control strategies, but none has been an unqualified success. Results have been good when well-trained staff with substantial resources were employed, but much poorer when less-well-equipped general health workers took over the programmes. Overall, it would seem most cost-effective for health workers to concentrate their efforts on the elimination of the limited number of larval habitat categories which commonly contribute a large fraction of the adult population. Insecticides and biological control agents should serve as supplements, not as alternatives, to environmental management. Genetic control strategies have currently no place in C. quinquefasciatus programmes.

Animals↗
PubMed2003

Efficacy of VectoBac (Bacillus thuringiensis variety israelensis) formulations for mosquito control in Australia.

Laboratory bioassays were conducted on the efficacy of a water-dispersible granule (WG) formulation of Bacillus thuringiensis variety israelensis (VectoBac WG; active ingredient [AI]: 3,000 Bti international toxic units [ITU]/mg) against third instars of six common Australian mosquito species, Aedes aegypti (L.), Ochlerotatus vigilax (Skuse), Ochlerotatus notoscriptus (Skuse), Culex sitiens Wiedemann, Culex annulirostris Skuse, and Culex quinquefasciatus Say. The normal model for log-linear mortality data was used to determine laboratory 48-h LC50 and LC95 values. The target mosquito species tested were extremely sensitive to the VectoBac WG formulation, with the most sensitive species (Cx. annulirostris and Cx. quinquefasciatus, LC95 value of 0.019 ppm) being twice as susceptible as the most tolerant (Oc. notoscriptus, LC95 value of 0.037 ppm). Cx. annulirostris was selected as a target species for a small-plot evaluation of VectoBac WG and VectoBac 12 aqueous solution (AS) ([AI]: 1,200 Bti ITU/mg) efficacy over time, in freshwater in southeastern Queensland, Australia. Replicated cohorts of caged third instars were exposed weekly to six concentrations of WG formulation (0.004-0.13 ppm) and three concentrations of the 12AS formulation (0.04-0.13 ppm). In water with high organic content, treatment concentrations of 0.008 ppm WG and 0.04 ppm 12AS and above produced significant larval control (> or = 96%) at 48 h posttreatment, with no residual control at week 1. Water quality was not affected by treatment with either formulation.

Aedes↗
PubMed2004

Bacillus thuringiensis variety kurstaki x aizawai applied to spruce flowers reduced Dioryctria abietella (Lepidoptera: Pyralidae) infestation without affecting seed quality.

We investigated the effects of Bacillus thuringiensis variety kurstaki x aizawai (Bt) on infestation levels of two lepidopteran insects as well as on seed quality in Norway spruce, Picea abies L. (Karst.) in central Sweden. Spruce flowers (female strobili) were sprayed with a 0.2% suspension (wt:wt) of the Bt preparation Turex 50 WP, 25,000 IU/mg in water. To expose even those lepidopteran larvae that feed exclusively embedded within the cone tissue, the Bt treatment was applied to open flowers, before they closed and developed into cones. The experimental design included three main factors: treatment (untreated control, water, or Bt), spruce genotype (three clones), and spraying time (spraying before, during, and after the phase of highest pollen receptivity). The Bt treatment reduced the proportion of cones infested by the cone worm Dioryctria abietella Den. et Schiff. (Lepidoptera: Pyralidae) from approximately 30 to 15%. There was no statistically significant treatment effect on the infestation rate of Cydia strobilella (L.) (Lepidoptera: Tortricidae). The Bt variety kurstaki x aizawai treatment caused no reduction in seed quality as measured by seed weight or percentage of nonfilled seeds. There was no difference in number of seeds per cone between the Bt-treated and untreated control cones. There was a significant effect of genotype on insect infestation rates, as well as on number of seeds per cone and seed weight. Neither level of insect damage nor any seed quality parameters were affected by time of application of the treatments.

Animals↗
PubMed2004

Molecular monitoring and evaluation of the application of the insect-pathogenic fungus Beauveria bassiana in southeast China.

AIMS: To monitor the fate of inundatively applied strains of Beauveria bassiana against Masson's pine caterpillar, Dendrolimus punctatus, in Magushan Forest, southeast China, and evaluate the potential environmental risks of biocontrol introduction. METHODS AND RESULTS: Filed samplings of mycosed cadavers were carried out continuously for more than one year after the inundative applications of two exotic B. bassiana strains. By employing four complementary molecular markers, the purified cultures from collections were characterized and the two released strains Bb17 and Bb13 were recovered with respective frequencies of 9.1 and 5.2%. The released strains were isolated from nontarget hosts. The genetic diversity of the population of B. bassiana in the trial plot changed dynamically over time and no single genotype strain dominated throughout the sampling period or at different seasons. The indigenous strains were observed to be predominant in the local environment. Co-infection and/or genetic recombination might occur between strains under natural conditions. CONCLUSION: Field applications of the biocontrol agent B. bassiana appear to pose no major risk to the environment. There was no evidence of displacement of indigenous strains of B. bassiana. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicate that the introduction of exotic B. bassiana strains can persist in local environment and infect nontarget insect hosts, highlighting the importance of safety assessment of the large-scale application of fungal biocontrol agents.

Animals↗