Process for controlling lepidopteron pests

Details Process for controlling lepidopteron pests Process for controlling lepidopteron pests

1992-09-08

2001-09-25

McKelvey, Terry (Department: 1636)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

C435S243000, C435S471000, C536S023100

Reexamination Certificate

active

06294184

ABSTRACT:

BACKGROUND OF THE INVENTION
The soil microbe
Bacillus thuringiensis
(B.t.) is a Gram-positive, spore-forming bacterium characterized by parasporal crystalline protein inclusions. These often appear microscopically as distinctively shaped crystals. The proteins are highly toxic to pests and specific in their activity. The toxin genes have been isolated and sequenced, and recombinant DNA-based B.t. products produced and approved. In addition, with the use of genetic engineering techniques, new approaches for delivering B.t. endotoxins to agricultural environments are under development, including the use of plants genetically engineered with endotoxin genes for insect resistance and the use of stabilized intact microbial cells as B.t. endotoxin delivery vehicles (Gaertner, F. H., L. Kim [1988] TIBTECH 6:S4-S7). Thus, isolated B.t. endotoxin genes are becoming commercially valuable.
Bacillus thuringiensis
produces a proteinaceous paraspore or crystal which is toxic upon ingestion by a susceptible insect host. Over the past 30 years, commercial use of B.t. pesticides has been largely restricted to a narrow range of lepidopteran (caterpillar) pests. Preparations of the spores and crystals of
B. thuringiensis
subsp.
kurstaki
have been used for many years as commercial insecticides for lepidopteran pests. For example,
B. thuringiensis
var.
kurstaki
HD-1 produces a crystal called a delta endotoxin which is toxic to the larvae of a number of lepidopteran insects.
In recent years, however, investigators have discovered B.t. pesticides with specificities for a much broader range of pests. For example, other species of B.t., namely
israelensis
and
san diego
(a.k.a.
B.t. tenebrionis,
a.k.a. M-7), have been used commercially to control insects of the orders Diptera and Coleoptera, respectively (Gaertner, F. H. [1989] “Cellular Delivery Systems for Insecticidal Proteins: Living and Non-Living Microorganisms,” in
Controlled Delivery of Crop Protection Agents
, R. M. Wilkins, ed., Taylor and Francis, New York and London, 1990, pp. 245-255). See also Couch, T. L. (1980) “Mosquito Pathogenicity of
Bacillus thuringiensis
var.
israelensis,” Developments in Industrial Microbiology
22:61-76; Beegle, C. C., (1978) “Use of Entomogenous Bacteria in Agroecosystems,”
Developments in Industrial Microbiology
20:97-104. Krieg, A., A. M. Huger, G. A. Langenbruch, W. Schnetter (1983)
Z. ang. Ent.
96:500-508, describe a B.t. isolate named
Bacillus thuringiensis
var.
tenebrionis,
which is reportedly active against two beetles in the order Coleoptera. These are the Colorado potato beetle,
Leptinotarsa decemlineata,
and
Agelastica alni.
Recently, many new subspecies of B.t. have been identified, and many genes responsible for active &dgr;-endotoxin proteins have been isolated (Höfte, H., H. R. Whiteley [1989]
Microbiological Reviews
52(2):242-255). Höfte and Whiteley classified 42 B.t. crystal protein genes into 14 distinct genes, grouped into 4 major classes based on amino-acid sequence and host range. The classes were CryI (Lepidoptera-specific), CryII (Lepidoptera- and Diptera-specific), CryIII (Coleoptera-specific), and CryIV (Diptera-specific). The discovery of strains specifically toxic to protozoan pathogens, animal-parasitic liver flukes (Trematoda), or mites (Acari) has broadened the potential B.t. product spectrum even further. With activities against unique targets, these novel strains retain their very high biological specificity; nontarget organisms remain unaffected. The availability of a large number of diverse B.t. toxins may also enable farmers to adopt product-use strategies that minimize the risk that B.t.-resistant pests will arise.
The cloning and expression of a B.t. crystal protein gene in
Escherichia coli
has been described in the published literature (Schnepf, H. E., H. R. Whitely [1981]
Proc. NatL Acad. Sci. USA
78:2893-2897). U.S. Pat. No. 4,448,885 and U.S. Pat. No. 4,467,036 both disclose the expression of B.t. crystal protein in
E. coli
. U.S. Pat. No. 4,853,331 discloses
B. thuringiensis
strain
san diego
(a.k.a.
B.t. tenebrionis,
a.k.a. M-7) which can be used to control coleopteran pests in various environments. U.S. Pat. No. 4,849,217 discloses
Bacillus thuringiensis
isolates active against the alfalfa weevil. One of the isolates disclosed is
B. thuringiensis
PS86A1 (NRRL B-18400).
BRIEF SUMMARY OF THE INVENTION
The subject invention concerns a novel process for controlling lepidopteran pests. This process results from the unexpected discovery that certain coleopteran-active B.t. isolates also have activity against lepidopteran pests, e.g., the diamondback moth (
Plutella xylostella
). This discovery was particularly surprising because known coleopteran-active isolates such as
Bacillus thuringiensis
var.
tenebrionis
(Krieg et al., supra) (hereinafter referred to as M-7) are not toxic to Lepidoptera.
More specifically, the subject invention process uses B.t. microbes, or variants thereof, and/or their toxins, to control lepidopteran pests. Specific B.t. microbes useful according to the invention are B.t. PS86A1, B.t. PS50C, and B.t. PS43F. Further, the subject invention also includes the use of variants of the B.t. isolates of the invention which have substantially the same lepidopteran-active properties as the specifically exemplified B.t. isolates. Procedures for making mutants are well known in the microbiological art. Ultraviolet light and nitrosoguanidine are used extensively toward this end.
The subject invention also includes the use of genes from the B.t. isolates of the invention which genes encode the lepidopteran-active toxins.
Still further, the invention also includes the treatment of substantially intact B.t. cells, and recombinant cells containing the genes of the invention, to prolong the lepidopteran activity when the substantially intact cells are applied to the environment of a target pest. Such treatment can be by chemical or physical means, or a combination of chemical and physical means, so long as the technique does not deleteriously affect the properties of the pesticide, nor diminish the cellular capability in protecting the pesticide. The treated cell acts as a protective coating for the pesticidal toxin. The toxin becomes available to act as such upon ingestion by a target insect.
Finally, the subject invention further concerns plants which have been transformed with genes encoding lepidopteran-active toxins.


REFERENCES:
patent: 4849217 (1989-07-01), Soares
patent: 4996155 (1991-02-01), Sick
patent: 5126133 (1992-06-01), Payne

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