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Seminar on biopesticides

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biopesticides are pesticides derived from such natural materials as animals, plants, bacteria and certain minerals

Publicado en: Ciencias

Seminar on biopesticides

  1. 1. Presented by- Panchali das M.Sc Biotechnolgy 3rd sem, BBAU 1 Biopesticides – Bacillus thuringiensis
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  3. 3. Introduction  As defined by the United States Environmental Protection Agency (EPA), biopesticides are pesticides derived from such natural materials as animals, plants, bacteria and certain minerals. 3
  4. 4. Types  Divided into three main groups:  Microbial Pesticides: Their active ingredient is a microorganism that occurs naturally. The microorganisms used in microbial biopesticides are bacteria, fungi, nematodes, protozoa, yeast and viruses.  Biochemical Pesticides: Naturally occurring substances that control pests by non-toxic mechanisms.  Include substances, such as insect sex pheromones, that interfere with mating, as well as various scented plant extracts that attract insect pests to traps.  Plant Pesticides: Pesticidal substances that plants produce from genetic material that has been added to the plant. 4
  5. 5. Microbes used as Biopesticides  Bacteria- Bacillus thuringiensis, commonly referred to as “Bt.”  Certain strains of Bacillus subtilis, Bacillus pumilus, Pseudomonas spp. and Streptomyces spp. increase yield and prevent plant diseases by outcompeting plant pathogens in the rhizosphere, producing anti-fungal compounds, and by promoting plant and root growth.  Viruses- Cydia pomonella granulosis virus (CpGV), cytoplasmic polyhedrosis virus {Cypovirus (CPV)}  Protozoan- Nosema ceranae  Fungi- Aschersonia aleyrodis , Metarhizium anisophliae  Require a wide host range , can cause allergies in man , in few cases they can infect man. 5
  6. 6. Table:11 Summary of desirable characteristics required by microbial pesticides Characteristic Bacteria Fungi Viruses Protozoa Time to kill Good Poor Poor Poor Easy to apply Yes Yes Yes Yes Storage Characteristics Good Poor Good Poor Environmental stability Poor Poor Poor Poor Safe to non target organisms Yes Yes Yes Yes Easy to produce Yes Yes Poor Poor 6
  7. 7. Biopesticide Microbial Pesticides Bacteria Biochemical Pesticides Biological Control Agents Bacillus thuringiensis 7
  8. 8. Bacillus thuringiensis  Bt is an aerobic or anaerobic facultative and sporulating bacterium.  It can remain latent in the environment even in adverse conditions for its development.  Bt can be found in soil, insects and their habitats, stored products, plants, forest, and aquatic environments.  B. thuringiensis can also serve as a source of toxic genes that can be expressed in plants and thus confer toxic property against different species of insect pests.  They have no toxicity to human & there is no withholding period on produce sprayed with Bt. 8
  9. 9. Contd..  Bt is used mainly to control larvae of insects in the Lepidoptera order (butterflies and moths).  It should be applied to the underside of leaves because:  most larvae feed on the underside of the leaves.  Bt breaks down faster in sunlight which will reduce its effectiveness.  This bacterium differs from other species belonging to this genus by the presence of a parasporal inclusion body (crystal) of protein origin, formed during sporulation.  These crystals are predominantly comprised of one or more proteins (Cry and Cyt toxins), also called δ- endotoxins. 9
  10. 10. What are Cry proteins?  Cry proteins are a large family of crystalline toxins produced by Bacillus thuringiensis.  Each Bt species/ strain produces a unique set of CRY proteins.  Genes that express the delta- endotoxins are called “cry genes” due to their crystalline phenotype.  Located on plasmids of large molecular weight.  Similarly, Cyt proteins are parasporal inclusion proteins from Bacillus thuringiensis that exhibits hemolytic (Cytolitic) activity.  Bt Cry and Cyt toxins belong to a class of bacterial toxins known as pore-forming toxins (PFT) or δ- endotoxins. 10
  11. 11. Contd..  There are two main groups of PFT: (i) the α-helical toxins,(includes Cry proteins) to this the α-helix region of the protein form a pore in the membrane and (ii) the β-barrel toxins,(includes Cyt proteins) these insert into the membrane by forming a β-barrel composed of βsheet hairpins from each monomer. In general, PFT producing-bacteria secrete their toxins and these toxins interact with specific receptors located on the host cell surface. 11
  12. 12. Diversity and Structure of Cry toxins  Cry proteins are specifically toxic to the insect orders:  Lepidoptera (butterflies and moths)  Diptera (flies and mosquitoes)  Orthoptera (grasshoppers and crickets)  Homoptera (aphids)  Coleoptera (beetles).  Cyt toxins are mostly found in Bt strains active against Diptera. 12
  13. 13. Contd..  Primary sequence identity among different gene sequences is the bases of the nomenclature of Cry and Cyt proteins and within each family there may be further levels or ranks of subfamily.  The cry genes were classified into four major classes based on their protein toxicity. Cry I : Lepidopteran specific. Cry II : Lepidopteran and Dipteran specific. Cry III : Coleopteran specific. Cry IV : Dipteran specific. Cry v & vi : Nematodes  The members of the three-domain family, the larger group of Cry proteins, are globular molecules containing three structural domains connected by single linkers. 13
  14. 14. Contd.. 1 2 3 Activated Toxin .. . . . . . ... . . . . Cry 1A Cry 1B Cry 3A Truncated forms in transgenic plants 0 600 1200 Amino acid residues 14 Comparison of the structures of different classes of Cry protein
  15. 15. 15 Structure of activated toxin demonstrating three distinct domains. Contd..
  16. 16. Mode of action 16 Anticarsia gemmatalis
  17. 17. Application of Bt technologies  Bt products- 17 Monterey Bt (Bacillus thuringiensis) is a naturally occurring soil bacteria ideal for controlling cabbageworm, tent caterpillars, gypsy moth, tomato hornworm and other leaf eating caterpillars. Safer Garden Dust is a highly selective biological pesticide containing Bacillus thuringiensis to control leaf-eating caterpillars and worms. After ingesting a treated portion of the leaf, caterpillars stop feeding within a few hours. Death occurs in a few days.
  18. 18. Contd..  Bt Plants- 18
  19. 19. Advantages  Difficult for insects to develop resistance to these pesticides.  Ability to multiply in the target cells.  No problem of toxic residue.  Permanent control of pest or long persisting effect.  No fear of environment pollution and hence ecofriendly. 19 Unprotected Cabbage Bt-protected Cabbage
  20. 20. Disadvantages  Rapidly degraded by UV light so residual action is slow.  Difficulty of culturing in large quantities.  All products applied followed by growers have not been scientifically verified.  Biopesticide is more costly and less readily available than conventional pesticide. Farmers with large crops may find it difficult to consistently use Biopesticide. 20
  21. 21. References  www.ncbi.com  Plant Biotechnology - The genetic manipulation of plants , Second Edition-Adrian Slater, Nigel Scott, and Mark Fowler  http://www.biology.50webs.com/bt.htm  en.wikipedia.org/wiki/Bacillus_thuringiensis 21
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