Generated by Foxit PDF Creator Foxit Software For evaluation only. Biotechnology in Plant Pathology

Transcription

1 Biotechnology in Plant Pathology

2 Plant Biotechnology Definition: The use of tissue culture & genetic engineering techniques to produce genetically modified plants that show improved desirable characteristics. Desirable characteristics include: Better yields & quality Greater resistance to adverse factors such as diseases, pests & environmental conditions Production of beneficial proteins such as plantibodies, vaccines, growth hormones, etc.

3 Plant Biotechnology (cont ) Transgenic plants 1. That tolerate abiotic stresses 2. Transformed with specific plant genes for resistance 3. Transformed with genes coding for antipathogen compounds 4. Transformed with nucleic acids that lead to silencing of pathogen genes 5. Transformed with combinations of resistance genes 6. Producing antibodies against pathogens

4 Plant Biotechnology (cont ) 1. Transgenic plants that tolerate abiotic stresses Example: transgenic eggplants are tolerant against osmotic stress (salinity), drought & low temperatures 2. Transformed with specific plant genes for resistance Example: transgenic hybrid rice display high resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae

5 Plant Biotechnology (cont ) 3. Transformed with genes coding for anti-pathogen compounds Example: groundnut plants transformed with PR proteins reduced disease incidence of blight caused by Sclerotinia minor by 36% 4. Transformed with nucleic acids that lead to silencing of pathogen genes Example: transgenic papaya plants are resistant to papaya ring spot virus (PRSV)

6 Plant Biotechnology (cont ) 5. Transformed with combinations of resistance genes Example: transgenic rice are resistant to rice blast caused by Pyricularia oryzae (teleomorph: Magnaporthe grisea) & abiotic stress such as high salinity 6. Producing antibodies against pathogens Still under research Example: transgenic plants producing antibodies shown to suppress tobacco mosaic virus (TMV), potato virus X, etc.

7 Plant Biotechnology (cont ) Genetic engineering techniques allow the detection, isolation, modification, transfer, & expression of single genes, or groups of related genes, from one organism to another. Genetic engineering technique is effective esp. in producing transgenic plants that are resistant to viral infection. Transgenic plants resistant to viruses include melon, squash, tomato, tobacco & papaya.

8 Genetically Modified Organisms (GMO) Herbicide resistant Insect resistant Note: Percent of total million hectares Source: USDA Economic Research Service, National Agricultural Statistics Service (2001)

9 Genetically Modified Organisms (GMO) Issues involved 1. The fear that foreign genes will get into human diet or animal food chain and cause allergies & other adverse health effects 2. Allergies: New proteins produced may cause allergic reactions in some people

10 GMO (cont ) Issues involved (cont ) 3. Intellectual property: Genetic materials that was previously available for everybody may be monopolized by some parties 4. Losing local varieties: Sustainable local varieties replaced with a few genetically engineered ones, farmers must buy seeds from large companies every year

11 GMO (cont ) Issues involved (cont ) 5. Threaten natural organisms: Due to new proteins produced 6. Threaten ecological balance: Via transfer of new genes to non-target organisms

12 Papaya Ring Spot: A Success Story Transgenic papaya variety resistant to papaya ring spot virus (PRSV) has saved the papaya industry in Hawaii & Middle East. Comparison of papaya ring spot development of susceptible papaya variety (left) and transgenic plants (right). Transgenic papaya plants look healthy (middle block) compared to susceptible variety that are almost destroyed by the virus. Source: Agrios (2005)

13 Transgenic papaya inoculated with PRSV from Hawaii (left) and nontransgenic papaya inoculated with PRSV from Hawaii (right). Note the resistance of transgenic papaya.

14 Papaya Ring Spot (cont ) Mechanism of resistant Gene silencing Addition of PRSV coat protein gene into papaya chromosomes Host defense mechanism will block nucleic acid replication process of the virus Virus unable to spread in host cells

15

16 Application of Biotechnology Breeding of resistant varieties 1. Tissue culture 2. Protoplast fusion 3. Genetic transformation

17 Application of Biotechnology (cont ) 1. Tissue culture The use of callus, single cells, or protoplast (cell without cell wall) Tissue culture plants have high genetic variability, some are resistant to certain pathogens

18

19 Application of Biotechnology (cont ) 2. Protoplast fusion Fusion of 2 or more protoplasts Addition of chromosomes give new characteristics for selection

20

21 Application of Biotechnology (cont ) 3. Genetic transformation ii. The process of inserting foreign genes into plant cells either artificially or naturally Most common used methods: i. Microprojectile bombardment (artificially) Agrobacterium tumefaciens vector system (naturally)

22 Application of Biotechnology (cont ) i. Microprojectile bombardment ii. Plant cells are bombarded with tiny spheres coated with target gene Agrobacterium tumefaciens vector system Incubate plant cells with Agrobacterium Agrobacterium has a plasmid called Ti that functions to insert the bacterial genes into host chromosomes Modified Ti plasmid will transfer target gene into host chromosomes

23 Microprojectile bombardment - gene gun

24 Agrobacterium tumefaciens vector system

25

26 Thank You

27 Techniques of molecular biology DNA and RNA extraction Gel electrophoresis Hybridisation PCR Cloning and Sequencing

28 2. Gel electrophoresis Separation based on size

29 Hybridisation A powerful tool that relies on Transfer and binding of single stranded DNA to a membrane Base-pairing of labeled probe DNA to target DNA (conditions can be varied to suit need) Ability to determine where labeled probe has bound to membrane using X-Ray film

30 Hybridisation Generated by Foxit PDF Creator Foxit Software

31 Plant disease journals Phytopathology Plant disease Journal of Phytopathology Plant pathology

32 reference Journal Wetzel, T., Candresse, T., Ravelonandro, M. and Dunez, J. (1991). A polymerase chain reaction assay adapted to plum pox potyvirus detection. Journal of Virological Methods 33, Books Hanold, D. (1993). Diagnostic methods applicable to viroids. In Diagnosis of Plant Virus Diseases, pp Edited by R.E. F. Matthews. Boca Raton, Florida: CRC Press. Turner, P.D. (1981). Oil Palm Diseases and Disorders, pp Kuala Lumpur: Oxford University Press.

33 Proceedings Vadamalai, G., Rezaian, M.A., Hanold, D. and Randles, J.W. (2004). Ribonuclease protection assay (RPA) as a potential tool for viroid detection. In Proceedings of the 6th Australasian Plant Virology Workshop. Gold Coast, Queensland, Australia. Website MPOPC (2005). Malaysian Palm Oil Promotion Council.