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  Section: General Biotechnology / Plant Biotechnology
 
 
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Biological Control of Plant Pathogens, Pests and Weeds

 
     
 

Genetic Engineering of Biocontrol Agents

Occurrence of a number of interactions among the microorganisms provides a broad opportunity for genetic engineering of microbial biocontrol agents directed at plant pathogens or other microorganisms against weeds and pests. Several biocontrol agents have been successfully employed for such purposes in experimental or commercial agriculture (Panopoulos, 1986).

 

The effectiveness of biocontrol agents can be intensified by gene splicing, gene cloning and transformations (Papavizas, 1987). It is, however, obvious that bacterial pathogenicity on plant is determined by several genes. Certain genes encode enzymes involved in the biosynthesis of phytotoxins, growth hormones or enzyme capable of degrading plant cell wall or other constituents. Since these genes are positively needed for pathogenesis, their inactivation (e.g. through deletion-replacement technique) would destroy the organisms, their pathogenic potential or reduce virulence (Panopoulos, 1986).

 

Papavizas (1985) has discussed the future prospects of some wild type strains of fungal antagonists (viz., Aspergillus, Chaetomium, Dendrostibella, Gliocladium, Penicillium, Sporidesmium, Talaromyces, Tetraspenna and Trichoderma) for biological control of soil borne diseases.

 

In India, at National Institute of Immunology (Nil), New Delhi some genes of Baculoviruses have been engineered to make them 'suicide' (self destroying) after they have infected and killed the insect pests.

 

Genetic material of Baculoviruses is covered by a protein coat called polyhedrin. It is synthesized by a gene of the viruses. Scientists at Nil have made a suicide squads of Baculoviruses by removing the polyhedrin gene. After application, the genetically engineered Baculoviruses infect and kill the larvae, and millions of viruses, after completing their life cycle, are released into the environment. Soon after release, viruses die within a few hour as they lack polyhedrin, therefore, fail to survive. By making the viruses crippled before application, possible risk’ associated with virus release can be completely eliminated. Field trials of these have also been conducted at Tamil Nadu Agricultural University, Coimbatore.
 

Content

Biological control of plant pathogens 

 

Inoculum

 

Historical background

 

Phyllosphere-phylloplane and rhizosphere-rhizoplane regions

 

Antagonism

 

 

Amensalism (antibiosis and lysis)

 

 

Competition

 

 

Predation and parasit­ism : Mycoparasitism, nematophagy and mycophagy

 

Application of biological control

 

 

Crop rotation

 

 

Irrigation

 

 

Alteration of soil pH

 

 

Organic amendments

 

 

Soil treatment with selected chemicals

 

 

Introduction of antagonists : Seed inoculation, vegetative part inoculation and soil inoculation

 

 

Use of mycorrhizal fungi

 

Genetic engineering of biocontrol agents

Biological control of insect pests

 

Microbial pesticidies

 

 

Bacterial, viral and fungal pesticides

 

 

Viral pesticides

 

 

Mycopesticides

Biological control of weeds

 

Mycoherbicides

 

Insects as biocontrol agents


 
     
 
 
     



     
 
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