Showing papers on "Bacillus thuringiensis published in 1990"
TL;DR: The results suggest that the potential for resistance development in pest populations is an important consideration for deployment of B. thuringiensis toxin genes in genetically-engineered crop plants and use in related tactics.
Abstract: Foliar applications of commercial formulations of the insecticidal spore-crystal protein complex of Bacillus thuringiensis subsp. kurstaki caused development of resistance in field populations of a major lepidopteran pest of vegetables, diamondback moth, Plutella xylostella (L.). Laboratory bioassays of larvae showed that the LC50 and LC95 for a field population of diamondback moth treated repeatedly with B. thuringiensis were 25 to 33 times greater than the respective LC50’s and LC95’s for two susceptible laboratory colonies. Mortality at the field rate of B. thuringiensis was 34-35% in two resistant populations compared with 90-100% in two susceptible laboratory colonies. The results suggest that the potential for resistance development in pest populations is an important consideration for deployment of B. thuringiensis toxin genes in genetically-engineered crop plants and use of B. thuringiensis in related tactics.
765 citations
TL;DR: A method for expressing insecticidal protein structural genes in cotton plant genomes by utilizing an Agrobacterium tumefaciens Ti plasmid-based transformation system and the modified Ti Plasmid is used to transform recipient plant cells.
Abstract: We have expressed truncated forms of the insect control protein genes of Bacillus thuringiensis var. kurstaki HD-1(cryIA(b) and HD-73 (cryIA(c) in cotton plants at levels that provided effective control of agronomically important lepidopteran insect pests. Total protection from insect damage of leaf tissue from these plants was observed in laboratory assays when tested with two lepidopteran insects, an insect relatively sensitive to the B.t.k. insect control protein, Trichoplusia ni (cabbage looper) and an insect that is 100 fold less sensitive, Spodoptera exigua (beet armyworm). Whole plants, assayed under conditions of high insect pressure with Heliothis zea (cotton bollworm) showed effective square and boll protection. Immunological analysis of the cotton plants indicated that the insect control protein represented 0.05% to 0.1% of the total soluble protein. We view these results as a major step towards the agricultural use of genetically modified plants with insect resistance in this valuable, high acreage crop.
588 citations
TL;DR: The statement that differences in midgut ICP receptors are a major determinant of differences in the insecticidal spectrum of the entire lepidopteran-specific ICP family is supported.
Abstract: To investigate the biochemical basis of the differences in the insecticidal spectrum of Bacillus thuringiensis insecticidal crystal proteins (ICPs), we performed membrane binding and toxicity assays with three different ICPs and three lepidopteran species. The three ICPs have different toxicity patterns in the three selected target species. Binding studies with these 125I-labeled ICPs revealed high-affinity saturable binding to brush border membrane vesicles of the sensitive species. ICPs with no toxicity against a given species did not bind saturably to vesicles of that species. Together with previous data that showed a correlation between toxicity and ICP binding, our data support the statement that differences in midgut ICP receptors are a major determinant of differences in the insecticidal spectrum of the entire lepidopteran-specific ICP family. Receptor site heterogeneity in the insect midgut occurs frequently and results in sensitivity to more than one type of ICP.
373 citations
TL;DR: Receptor binding studies show that resistance of a laboratory-selected Plodia interpunctella strain to a Bacillus thuringiensis insecticidal crystal protein is correlated with a 50-fold reduction in affinity of the membrane receptor for this protein.
Abstract: Receptor binding studies show that resistance of a laboratory-selected Plodia interpunctella strain to a Bacillus thuringiensis insecticidal crystal protein (ICP) is correlated with a 50-fold reduction in affinity of the membrane receptor for this protein. The strain is sensitive to a second type of ICP that apparently recognizes a different receptor. Understanding the mechanism of resistance will provide strategies to prevent or delay resistance and hence prolong the usefulness of B. thuringiensis ICPs as environmentally safe insecticides.
365 citations
TL;DR: The host range and relative efficacy of three purified Bacillus thuringiensis insect control proteins were determined against 17 different agronomically important insects representing five orders and one species of mite to determine the amount of B. kurstaki protein required to inhibit larval growth by 50%.
278 citations
Patent•
09 May 1990
TL;DR: In this paper, the Bacillus thuringiensis genes encoding toxins which are active against lepidopteran insects have been cloned from novel lepticopteran-active B. thuringienis microbes.
Abstract: Novel Bacillus thuringiensis genes encoding toxins which are active against lepidopteran insects have been cloned from novel lepidopteran-active B. thuringiensis microbes. The DNA encoding the B. thuringiensis toxins can be used to transform various prokaryotic and eukaryotic microbes to express the B. thuringiensis toxins. These recombinant microbes can be used to control lepidopteran insects in various environments.
232 citations
TL;DR: Theδ-endotoxin fromBacillus thuringiensis subspecieskurstaki strain HD1-9 is almost 400 times more potent than the δ- endotoxins from strain HD-73 as a gypsy moth larvicide.
Abstract: The delta-endotoxin from Bacillus thuringiensis subspecies kurstaki strain HD1-9 is almost 400 times more potent than the delta-endotoxin from strain HD-73 as a gypsy moth larvicide. The two delta-endotoxins compete for a high-affinity binding site on the brush border membrane of larval gypsy moth midguts. The affinity for the delta-endotoxin from strain HD-73 is much greater than the affinity for the delta-endotoxin from strain HD1-9.
163 citations
152 citations
Patent•
11 Apr 1990
TL;DR: In this paper, the authors provide a process for transforming a corn plant to be transformed using a microprojectile bombardment of friable embryogenic callus from the plant to transform it.
Abstract: Fertile transgenic Zea mays (corn) plants which stably express heterologous DNA which is heritable are provided along with a process for producing said plants. The preferred process comprises the microprojectile bombardment of friable embryogenic callus from the plant to be transformed. The process may be applicable to other graminaceous cereal plants which have not proven stably transformable by other techniques.
118 citations
TL;DR: Data indicate that the expression of the B. thuringiensis delta-endotoxin gene by a baculovirus in insect cells produces material with insecticidal activity, which is significant for the genetic engineering of virus insecticides.
Abstract: The δ-endotoxin gene from Bacillus thuringiensis subsp. kurstaki HD-73 was inserted into Autographa californica nuclear polyhedrosis virus (AcMNPV) using two transfer vector systems. In the first, the δ-endotoxin gene was placed under the control of the polyhedrin gene promoter in lieu of the polyhedrin coding sequences, thus deriving a polyhedrin-negative virus. In the second, it was inserted under the control of a copy of the AcMNPV p10 promoter positioned upstream of the polyhedrin gene to produce a polyhedrin-positive virus. Analysis of infected cell extracts showed that the δ-endotoxin was expressed in insect cells as 130K, 62K and 44K proteins, with peak syntheses at 18 h post-infection. Each of these products reacted with antisera specific for the complete protoxin and the cleaved, active form. When extracts from the cells infected with the polyhedrin-negative virus were fed to Trichoplusia ni larvae, feeding by the insects was inhibited and deaths occurred that were inconsistent with virus infection. This effect was also observed after the inoculum had been treated with detergents to inactivate virus particles prior to feeding to the larvae. These data indicate that the expression of the B. thuringiensis δ-endotoxin gene by a baculovirus in insect cells produces material with insecticidal activity. The biological activities of the two recombinant viruses were assessed in conventional bioassay tests by feeding virus particles or occlusion bodies to the insects. The polyhedrin-negative virus preparation appeared to be contaminated with endotoxin which inhibited feeding of the insects and prevented determination of the LD50 value. The polyhedrin-positive virus had an LD50 value about twofold higher than that of unmodified AcMNPV. The significance of these data for the genetic engineering of virus insecticides is discussed.
115 citations
TL;DR: Two commercially important strains (NRD-12 and HD-1) of the entomopathogenic bacterium Bacillus thuringiensis subsp.
Abstract: Two commercially important strains (NRD-12 and HD-1) of the entomopathogenic bacterium Bacillus thuringiensis subsp. kurstaki each contain three genes of partially identical sequence coding for three classes of 130-135 kDa protoxins (termed the 4.5, 5.3 and 6.6 protoxins) that display toxicity towards various lepidopteran larvae. These gene products combine to form the intracellular bipyramidal P1 crystal. Each of the genes from both strains was cloned and expressed in Escherichia coli. Analysis of the cloned genes at the restriction-endonuclease level revealed no detectable differences among genes within a particular gene class. The composition of the P1 crystal from both strains was quantitatively analysed by CNBr cleavage of the purified P1 crystal, with the purified recombinant gene products as reference proteins. Independent verification of the presence of high 6.6-protoxin gene product in the P1 crystal was provided by a rapid in vitro lawn cell toxicity assay directed against a Choristoneura fumiferana (CF-1) insect cell line. The results indicate that, although all three gene products are represented within the P1 crystal of either NRD-12 or HD-1, only the contents of the 4.5 and 5.3 protoxins vary between the two crystals, whereas the 6.6 protoxin contents are similar and represent approximately one-third of the P1 crystal in either strain.
TL;DR: It is concluded that the N- and C-terminal regions of the protoxin are two multidomain regions which give unique structural and biological properties to the molecule.
Abstract: Trypsin is shown to generate an insecticidal toxin from the 130-kDa protoxin of Bacillus thuringiensis subsp. kurstaki HD-73 by an unusual proteolytic process. Seven specific cleavages are shown to occur in an ordered sequence starting at the C-terminus of the protoxin and proceeding toward the N-terminal region. At each step, C-terminal fragments of approximately 10 kDa are produced and rapidly proteolyzed to small peptides. The sequential proteolysis ends with a 67-kDa toxin which is resistant to further proteolysis. However, the toxin could be specifically split into two fragments by proteinases as it unfolded under denaturing conditions. Papain cleaved the toxin at glycine 327 to give a 34.5-kDa N-terminal fragment and a 32.3-kDa C-terminal fragment. Similar fragments could be generated by elastase and trypsin. The N-terminal fragment corresponds to the conserved N-terminal domain predicted from the gene-deduced sequence analysis of toxins from various subspecies of B. thuringiensis, and the C-terminal fragment is the predicted hypervariable sequence domain. A double-peaked transition was observed for the toxin by differential scanning calorimetry, consistent with two or more independent folding domains. It is concluded that the N- and C-terminal regions of the protoxin are two multidomain regions which give unique structural and biological properties to the molecule.
TL;DR: The genes encoding the toxic determinants of Bacillin sphaericus have been expressed in a nontoxic and a toxic strain of Bacillus thuringiensis subsp.
Abstract: The genes encoding the toxic determinants of Bacillus sphaericus have been expressed in a nontoxic and a toxic strain of Bacillus thuringiensis subsp. israelensis. In both cases, the B. sphaericus toxin proteins were produced at a high level during sporulation of B. thuringiensis and accumulated as crystalline structures. B. thuringiensis transformants expressing B. sphaericus and B. thuringiensis subsp. israelensis toxins did not show a significant enhancement of toxicity against Aedes aegypti, Anopheles stephensi, and Culex pipiens larvae.
TL;DR: Southern and Western blots show that InA‐related sequences are common among other B. thuringiensis subspecies, and culture filtrates from subspecies expressing InA were toxic when injected in Trichoplusia ni larvae, whereas filtrate from a strain negative in Western blot had no effect when injected.
Abstract: Summary
The gene for the secreted neutral metalloprotease, immune inhibitor A (InA), from Bacillus thuringiensis var. alesti has been cloned and sequenced. The deduced amino acid sequence has been confirmed by partial amino acid sequencing. The central part of the amino acid sequence showed similarity to the active site in thermolysin. Southern and Western blots show that InA-related sequences are common among other B. thuringiensis subspecies. In Western blots, 17 out of 25 tested species gave a positive signal. Culture filtrates from subspecies expressing InA were toxic when injected in Trichoplusia ni larvae, whereas filtrate from a strain negative in Western blot had no effect when injected. The LD50 dose of purified InA protein injected in T. ni larvae was 12.5 ± 2.5 ng per mg of larval body weight.
01 Jan 1990
TL;DR: The results suggest that plasmid transfer between strains of B. thuringiensis occurs in nature, resulting in the production of new combinations of delta-endotoxins within populations of the bacteria.
Abstract: To determine the possibility of plasmid transfer occurring between strains of Bacillus thuringiensis in infected lepidopterous larvae, Galleria mellonella and Spodoptera littoralis were infected with two or more strains of B. thuringiensis and the resulting bacteria from the dead insects were examined for plasmid transfer. Transfer rates of plasmids coding for crystal production and tetracycline resistance were high, reaching levels similar to those obtained in laboratory broth cultures. Transfer was higher in G. mellonella than S. littoralis, probably due to the greater ability of B. thuringiensis to colonize the larvae. In broth cultures, B. thuringiensis was also able to transfer plasmids into sporeforming bacteria present in soil samples. The results suggest that plasmid transfer between strains of B. thuringiensis occurs in nature, resulting in the production of new combinations of delta-endotoxins within populations of the bacteria.
TL;DR: The CryIIB protein was found to be highly toxic to Lymantria dispar, Heliothis virescens and Trichoplusia ni, and was not toxic to Aedes aegypti.
Abstract: DNA hybridization with the insecticidal crystal protein gene cryllA (formerly cryBl) of Bacillus thuringiensis supspecies kurstaki has shown that subspecies kurstaki contains a cryllA-related sequence in addition to the cryllA gene (Donovan et al., 1988a). We have cloned the cryllA-related sequence and have determined that the sequence, which has been designated cryllB, is 89% identical to the cryllA gene. Recombinant B. thuringiensis cells harbouring the cloned cryllB gene produced very little CryllB protein. A high level of production of the CryllB protein was achieved by fusing the regulatory region of the crylllA crystal protein gene to the cryllB gene. The CryllB protein was found to be highly toxic to Lymantria dispar, Heliothis virescens and Trichoplusia ni, and was not toxic to Aedes aegypti.
TL;DR: Seven replication origins from resident plasmids of Bacillus thuringienis subsp.
Abstract: Seven replication origins from resident plasmids of Bacillus thuringienis subsp. kurstaki HD263 and HD73 were cloned in Escherichia coli. Three of these replication origins, originating from plasmids of 43, 44, and 60 MDa, were used to construct a set of compatible shuttle vectors that exhibit structural and segregational stability in the Cry- strain B. thuringiensis HD73-26. These shuttle vectors, pEG597, pEG853, and pEG854, were designed with rare restriction sites that permit various adaptations, including the construction of small recombinant plasmids lacking antibiotic resistance genes. The cryIA(c) and cryIIA insecticidal crystal protein genes were inserted into these vectors to demonstrate crystal protein production in B. thuringiensis. Introduction of a cloned cryIA(c) gene from strain HD263 into a B. thuringiensis subsp. aizawai strain exhibiting good insecticidal activity against Spodoptera exigua resulted in a recombinant strain with an improved spectrum of insecticidal activity. Shuttle vectors of this sort should be valuable in future genetic studies of B. thuringiensis as well as in the development of B. thuringiensis strains for use as microbial pesticides. Images
TL;DR: The nucleotide sequence analysis and the toxicity studies showed that this novel crystal protein gene falls into a new cryl gene subclass, and it is proposed that this subclass be referred to as cryIE.
Abstract: Only one of the four lepidoptera-specific crystal protein subclasses (CryIC) Bacillus thuringiensis was previously shown to be highly toxic against several Spodoptera species. By using a cryIC-derived nucleotide probe, DNA from 25 different strains of B. thuringiensis was screened for the presence of homologous sequences. A putative crystal protein gene, considerably different from the cryIC gene subclass, was identified in the DNA of strain 4F1 (serotype kenyae) and cloned in Escherichia coli. Its nucleotide sequence was determined and appeared to contain several features typical for a crystal protein gene. Furthermore, the region coding for the N-terminal part of the putative toxic fragment showed extensive homology to subclass cryIA sequences derived from gene BtII, whereas the region coding for the C-terminal part appeared to be highly homologous to the cryIC gene BtVI. With an anti-crystal protein antiserum, a polypeptide of the expected size could be demonstrated in Western immunoblots, onto which a lysate of E. coli cells harboring the putative gene, now designated as BtXI, had been transferred. Cells expressing the gene appeared to be equally toxic against larvae of Spodoptera exigua as recombinant cells expressing the BtVI (cryIC)-encoded crystal protein. However, no toxicity against larvae of Heliothis virescens, Mamestra brassicae, or Pieris brassicae could be demonstrated. The nucleotide sequence analysis and the toxicity studies showed that this novel crystal protein gene falls into a new cryl gene subclass. We propose that this subclass be referred to as cryIE.
Book•
01 Jan 1990
TL;DR: Part 1 Bacillus thuringiensis subsp.
Abstract: Part 1 Bacillus thuringiensis subsp. israelensis(B.t.i.): discovery of Bacillus thuringiensis israelensis, Joel Margalit characterizations and prospective view of Bacillus thuringiensis israelensis, Huguette de Barjac parasporal body of Bacillus thuringiensis israelensis - structure, protein composition and toxicity, Brian A.Federici et al mechanism of action of Bacillus thuringiensis israelensis parasporal body, Chris N.Chilcott et al genetics of Bacillus thuringiensis israelensis, Vaithilingam Sekar cloning of Bacillus thuringiensis israelensis mosquito toxin genes, Thomas M. Boyle and Donald H.Dean transfer of the Bacillus thuringiensis israelensis mosquiticidal toxin gene into mosquito larval food, Kathleen C.Raymond et al potential for improved formulations of Bacillus thuringiensis israelensis through standardization and fermentation development, Howard T.Dulmage et al activity, field efficacy and use of Bacillus thuringiensis israelensis against mosquitoes, Mir S.Mulla progress in the biological control of black flies with Bacillus thuringiensis israelensis, with emphasis on temperate climates, Daniel P.Molloy use of Bacillus thuringiensis israelensis for onchocerciasis control in West Africa, Pierre Guillet et al mammalian safety of Bacillus thuringiensis israelensis, Joel P.Siegel and John A.Shadduck. Part 2 Bacillus sphaericus: introduction to the study of Bacillus sphaericus as a mosquito control agent, Samuel Singer classification of Bacillus sphaericus strains and comparative toxicity to mosquito larvae, Huguette de Barjac the mosquito larval toxin of Bacillus sphaericus, Elizabeth W.Davidson and Allan A.Ousten genetics of Bacillus sphaericus, William F.Burke, Jr. and Karen A.Orzech local production of Bacillus sphaericus, Amaret Bhumiratana persistence of formulation of Bacillus sphaericus, Lawrence A.Lacey formulations and persistence of Bacillus sphaericus in Culex quinquefasciatus larval sites in tropical Africa, Jean-Marc Hougard field trials of Bacillus sphaericus for mosquito control, Han Heng Yap mammalian safety of Bacillus sphaericus, Joel P.Siegel and John A.Shadduck. Part 3 The future: the future of bacterial control of mosquito and black fly larvae, Donald J.Sutherland.
TL;DR: An improved high-performance liquid chromatography separation was developed to detect and quantify beta-exotoxin production in Bacillus thuringiensis culture supernatants, and a new exotoxin was discovered, more specific than type I beta-Exotoxin and very active against the Colorado potato beetle, Leptinotarsa decemlineata.
Abstract: An improved high-performance liquid chromatography separation was developed to detect and quantify beta-exotoxin production in Bacillus thuringiensis culture supernatants Exotoxin production was assigned to a plasmid in five strains, from three subspecies (B thuringiensis subsp thuringiensis serotype 1, B thuringiensis subsp tolworthi serotype 9, and B thuringiensis subsp darmstadiensis serotype 10) A new exotoxin, called type II beta-exotoxin in this report, was discovered in B thuringiensis subsp morrisoni serotype 8ab, purified, and partially characterized This material is more specific than type I beta-exotoxin and is very active against the Colorado potato beetle, Leptinotarsa decemlineata
TL;DR: In infected Spodoptera frugiperda cells, the cryIA(b) gene was expressed at a high level without interference with Ac NPV production, and the toxicity of the crystal protein expressed by AcNPV recombinants was comparable with that of the Crystal Protein expressed by a corresponding Escherichia coli recombinant.
Abstract: Baculoviruses are insect pathogens with a relatively slow speed of action, and this has limited their use as control agents of insect pests. Introduction into baculoviruses of genes which code for proteins interfering specifically with insect metabolism or metamorphosis, such as toxins, hormones, and enzymes, may enhance the pathogenicity of these viruses. The complete insecticidal crystal protein gene cryIA(b) of Bacillus thuringiensis subsp. aizawai 7.21 was engineered into the nuclear polyhedrosis virus of Autographa californica (AcNPV) in place of the polyhedrin gene. In infected Spodoptera frugiperda cells, the cryIA(b) gene was expressed at a high level without interference with AcNPV production. The crystal protein was found in the cytoplasm of S. frugiperda cells, mainly as large crystals with an ultrastructure similar to that of B. thuringiensis crystals. Infected-cell extracts inhibited feeding of the large cabbage white Pieris brassicae. The toxicity of the crystal protein expressed by AcNPV recombinants was comparable with that of the crystal protein expressed by a corresponding Escherichia coli recombinant.
TL;DR: Two highly related crystal protein genes from Bacillus thuringiensis subsp.
Abstract: Two highly related crystal protein genes from Bacillus thuringiensis subsp. kurstaki HD-1, designated cryIIA and cryIIB (previously named cryB1 and cryB2, respectively), were used to study host range specificity. Their respective gene products are 87% identical but exhibit different toxicity spectra; CryIIA is toxic to both mosquito and tobacco hornworm larvae, whereas CryIIB is toxic only to the latter. Hybrids of the cryIIA and cryIIB genes were generated, and their resultant gene products were assayed for toxicity. A short segment of CryIIA corresponding to residues 307 through 382 was shown to be sufficient for altering host range specificity-i.e., when this region replaced the corresponding segment of CryIIB, the resulting hybrid protein acquired toxicity against mosquitoes. The CryIIA and CryIIB polypeptides differ by only 18 amino acids in this region, indicating that very few amino acid changes can have a substantial effect on the toxicity spectra of these proteins.
TL;DR: Optimal conditions were found to be low-copy-number plasmid (pBR322 ori), 48 h of growth, in lon+ cells, and a change of the gene's second codon to AAA can improve expression by two to three fold but is undetectable in the presence of a strong E. coli promoter.
TL;DR: From an alignment of the protein delta-endotoxins of Bacillus thuringiensis, certain structural and functional domains can be inferred which may shed light on the mode of action of these toxins.
Abstract: The protein δ-endotoxins of Bacillus thuringiensis are a commercially and environmentally important class of highly specific insecticides. From an alignment of their sequences, certain structural and functional domains can be inferred which may shed light on the mode of action of these toxins.
Patent•
16 Nov 1990TL;DR: In this article, it was shown that Bacillus thuringiensis delta-endotoxins produced by the mutant or variant B. thuringienis will have an activity directed towards the same pest insects as its parent B. tenebrionis, such as against lipidopterans, dipterans, and coleopterans.
Abstract: This invention relates to mutants or variants of Bacillus thuringiensis producing high amounts of active delta-endotoxins. The delta-endotoxins produced by the mutant or variant B. thuringiensis will have an activity directed towards the same pest insects as its parent B. thuringiensis delta-endotoxins, such as against lipidopterans (mutants from B. thuringiensis subsp. kurstaki or subsp. aizawai), dipterans (mutants from B. thuringiensis subsp. israelensis) or coleopterans (mutants from B. thuringiensis subsp. tenebrionis).
TL;DR: Bacillus thuringiensis var.
Abstract: Bacillus thuringiensis var. kurstaki (B.t.-k) is a microbial pesticide which has been widely used for over 30 years. Its safety for a human population living in sprayed areas has never been tested. Surveillance for human infections caused by B.t.-k among Lane County, Oregon residents was conducted during two seasons of aerial B.t.-k spraying for gypsy moth control. Bacillus isolates from cultures obtained for routine clinical purposes were tested for presence of Bacillus thuringiensis (B.t.). Detailed clinical information was obtained for all B.t.-positive patients. About 80,000 people lived in the first year's spray area, and 40,000 in the second year's area. A total of 55 B.t.-positive cultures were identified. The cultures had been taken from 18 different body sites or fluids. Fifty-two (95 percent) of the B.t. isolates were assessed to be probable contaminants and not the cause of clinical illness. For three patients, B.t. could neither be ruled in nor out as a pathogen. Each of these three B.t.-posit...
TL;DR: Two truncated Bacillus thuringiensis crystal protein genes, belonging to the classes cryIA(b) and cryIC and both coding for insecticidal N-terminal fragments of the corresponding crystal proteins, were translationally fused.
Abstract: Two truncated Bacillus thuringiensis crystal protein genes, belonging to the classes cryIA(b) and cryIC and both coding for insecticidal N-terminal fragments of the corresponding crystal proteins, were translationally fused. Expression of the gene fusion in Escherichia coli showed a biologically active protein with a toxicity spectrum that overlapped those of both contributing crystal proteins.
TL;DR: Results from this study suggest that NRD-12 is not more toxic to S. exigua than HD-1, that different protein types have variable host activity, and that other B. thuringiensis components are not required for T. ni toxicity but that other components such as spores might be required for S.Exigua toxicity.
Abstract: The toxicities to neonate Spodoptera exigua and Trichoplusia ni of lyophilized powders obtained from sporulated liquid cultures (referred to as sporulated cultures) and Escherichia coli-expressed P1 [cryIA(a) cryIA(b) cryIA(c)] protoxins from three-gene strains of NRD-12 and HD-1 of Bacillus thuringiensis subsp. kurstaki were determined by using diet incorporation bioassays. Although sporulated cultures from both strains were more toxic to T. ni than S. exigua, there were no differences in toxicity between NRD-12 and HD-1. Toxicities of the three individual P1 protoxins against S. exigua varied by at least fivefold, with the cryIA(b) protein being the most toxic. These same protoxins varied in toxicity against T. ni by at least 16-fold, with the cryIA(c) protein being the most toxic. However, when tested against either S. exigua or T. ni, there were no differences in toxicity between an NRD-12 P1 protoxin and the corresponding HD-1 P1 protoxin. Comparing the toxicities of individual protoxins with that of sporulated cultures demonstrates that no individual protoxin was as toxic to S. exigua as the sporulated cultures. However, this same comparison against T. ni shows that both the cryIA(b) and cryIA(c) proteins are at least as toxic as the sporulated cultures. Results from this study suggest that NRD-12 is not more toxic to S. exigua than HD-1, that different protein types have variable host activity, and that other B. thuringiensis components are not required for T. ni toxicity but that other components such as spores might be required for S. exigua toxicity.
TL;DR: Starch granules without additives were seldom fed upon by larvae, but it was possible to make the granules even more acceptable to larvae than corn foliage, and the best feeding responses were to mixtures containing lipid, sugar, and protein.
Abstract: A starch formulation of Bacillus thuringiensis Berliner is being developed as a component in a pest management system to control Ostrinia nubi/alis (Hubner). Palatability is one property of starch formulations which must be investigated; this study was done to identify materials that will cause O. nubi/alis larvae to feed readily on starch granules. A two-choice behavioral bioassay was developed for evaluating phagostimulants in starch gran ules (without B. thuringiensis). Various materials were tested: compounds reported in the literature as feeding stimulants, the artificial diet for the species, corn foliage, corn oil, and the commercial feeding stimulant, Coax. Starch granules without additives were seldom fed upon by larvae, but it was possible to make the granules even more acceptable to larvae than corn foliage. The best feeding responses were to mixtures containing lipid, sugar, and protein. Coax was the most effective material tried; for example, in bioassays, the ratio of larvae that chose granules with Coax over those with only starch was 320:1, and the ratio of larvae choosing granules with Coax over corn leaf disks was 11.5:1. In greenhouse tests, phagostimulants increased the effectiveness of granules containing B. thuringiensis for killing O. nubilalis larvae. For example, when Coax was added to the granules, the amount of B. thuringiensis used could be reduced by 75% without reducing mortality.