Toxins active against pests

Details Toxins active against pests Toxins active against pests

2000-06-07

2003-05-27

Navarro, Mark (Department: 1645)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carbohydrates or derivatives

C536S023500, C514S012200, C435S243000, C435S252200, C435S252300, C435S252310, C435S419000, C800S301000, C800S302000

Reexamination Certificate

active

06570005

ABSTRACT:

BACKGROUND OF THE INVENTION
The black cutworm (
Agrotis ipsilon
(Hufnagel); Lepidoptera: Noctuidae) is a serious pest of many crops including maize, cotton, cole crops (Brassica, broccoli, cabbages, Chinese cabbages), and turf. Secondary host plants include beetroots, Capsicum (peppers), chickpeas, faba beans, lettuces, lucerne, onions, potatoes, radishes, rape (canola), rice, soybeans, strawberries, sugarbeet, tobacco, tomatoes, and forest trees. In North America, pests of the genus Agrotis feed on clover, corn, tobacco, hemp, onion, strawberries, blackberries, raspberries, alfalfa, barley, beans, cabbage, oats, peas, potatoes, sweetpotatoes, tomato, garden flowers, grasses, lucerne, maize, asparagus, grapes, almost any kind of leaf, weeds, and many other crops and garden plants. Other cutworms in the Tribe Agrotini are pests, in particular those in the genus Feltia (e.g.,
F. jaculifera
(Guenée); equivalent to
ducens subgothica
) and Euxoa (e.g.,
E. messoria
(Harris),
E. scandens
(Riley),
E. auxiliaris
Smith,
E. detersa
(Walker),
E. tessellata
(Harris),
E. ochrogaster
(Guenée). Host plants include various crops, including rape.
Cutworms are also pests outside North America, and the more economically significant pests attack chickpeas, wheat, vegetables, sugarbeet, lucerne, maize, potatoes, turnips, rape, lettuces, strawberries, loganberries, flax, cotton, soybeans, tobacco, beetroots, Chinese cabbages, tomatoes, aubergines, sugarcane, pastures, cabbages, groundnuts, Cucurbita, turnips, sunflowers, Brassica, onions, leeks, celery, sesame, asparagus, rhubarb, chicory, greenhouse crops, and spinach. The black cutworm
A. ipsilon
occurs as a pest outside North America, including Central America, Europe, Asia, Australasia, Africa, India, Taiwan, Mexico, Egypt, and New Zealand.
Cutworms progress through several instars as larvae. Although seedling cutting by later instar larvae produces the most obvious damage and economic loss, leaf feeding commonly results in yield loss in crops such as maize. Upon reaching the fourth larval instar, larvae begin to cut plants and plant parts, especially seedlings. Because of the shift in feeding behavior, economically damaging populations may build up unexpectedly with few early warning signs. Their nocturnal habit and behavior of burrowing into the ground also makes detection problematic. Large cutworms can destroy several seedlings per day, and a heavy infestation can remove entire stands of crops.
Cultural controls for
A. ipsilon
such as peripheral weed control can help prevent heavy infestations; however, such methods are not always feasible or effective. Infestations are very sporadic, and applying an insecticide prior to planting or at planting has not been effective in the past. Some baits are available for control of cutworms in crops. To protect turfgrass such as creeping bentgrass, chemical insecticides have been employed. Use of chemical pesticides is a particular concern in turf because of the close contact the public has with treated areas (e.g., golf greens, athletic fields, parks and other recreational areas, professional landscaping, home lawns). Natural products (e.g., nematodes, azadirachtin) generally perform poorly. To date,
Bacillus thuringiensis
products have not been widely used to control black cutworm because highly effective toxins have not been available.
The soil microbe
Bacillus thuringiensis
(B.t.) is a Gram-positive, spore-forming bacterium. Most strains of B.t. do not exhibit pesticidal activity. Some B.t. strains produce, and can be characterized by, parasporal crystalline protein inclusions. These “&dgr;-endotoxins” are different from exotoxins, which have a non-specific host range. These inclusions often appear microscopically as distinctively shaped crystals. The proteins can be highly toxic to pests and specific in their toxic activity. Certain B.t. toxin genes have been isolated and sequenced, and recombinant DNA-based B.t. products have been produced and approved for use. In addition, with the use of genetic engineering techniques, new approaches for delivering B.t. toxins to agricultural environments are under development, including the use of plants genetically engineered with B.t. toxin genes for insect resistance and the use of stabilized intact microbial cells as B.t. toxin delivery vehicles (Gaertner, F. H., L. Kim [1988
] TIBTECH
6:S4-S7). Thus, isolated B.t. endotoxin genes are becoming commercially valuable.
Commercial B.t. pesticides were originally used against only 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 crystalline &dgr;-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.
Various subspecies of B.t. have been identified, and 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 B.t. crystal protein genes into four major classes. 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 other pests has been reported (Feitelson, J. S., J. Payne, L. Kim [1992
] Bio/Technology
10:271-275). CryV has been proposed to designate a class of toxin genes that are nematode-specific. Lambert et al. (Lambert, B., L. Buysse, C. Decock, S. Jansens, C. Piens, B. Saey, J. Seurinck, K. van Audenhove, J. Van Rie, A. Van Vliet, M. Peferoen [1996
] Appl. Environ. Microbiol
62(1):80-86) and Shevelev et al. ([1993
] FEBS Lett.
336:79-82) describe the characterization of Cry9 toxins active against lepidopterans. For example, as stated in the abstract of Lambert et al., the Cry9Ca1 crystal protein has the typical features of the Lepidoptera-active crystal proteins such as five conserved sequence blocks. Also, it is truncated upon trypsin digestion to a toxic fragment of 68.7 kDa by removal of 43 amino acids at the N terminus and the complete C-terminal half after conserved sequence block 5. Published PCT applications WO 94/05771 and WO94/24264 also describe B.t. isolates active against lepidopteran pests. Gleave et al. ([1991] JGM 138:55-62) and Smulevitch et al. ([19911
]FEBS Lett.
293:25-26) also describe B.t. toxins. A number of other classes of B.t. genes have now been identified.
PCT application WO96/05314 discloses PS86W1, PS86V1, and other B.t. isolates active against lepidopteran pests. B.t. proteins with activity against members of the family Noctuidae are described by Lambert et al., supra. As a result of extensive research and investment of resources, other patents have issued for new B.t. isolates and new uses of B.t. isolates. See Feitelson et al., supra, for a review. See also WO 98/18932 and WO 99/57282. WO 94/21795 and Estruch, J. J. et al. ([1996
] PNAS
93:5389-5394) describe toxins obtained from Bacillus microbes. These toxins are reported to be produced during vegetative cell growth and were thus termed vegetative insecticidal proteins (VIP). These toxins were reported to be distinct from crystal-forming &dgr;-endotoxins. Activity of these toxins against certain lepidopteran pests was reported.
Notwithstanding the foregoing, the discovery of new B.t. isolates, pesticidal proteins, genes that encode pesticidal proteins, and new uses of known B.t. isolates and toxins remains an empirical art.
BRIEF DESCRIPTION OF THE INVENTION
The subject invention concerns materials and methods useful in the control of non-mammalian pests and, particularly, plant pests. In a specific embodiment, the subject invention provides new toxins useful for the control of lepidopterans

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