Question

Define biocontrol agent and write a short note on the mechanism of action of a biocontrol agent?

Write a note on the importance of molecular markers in agriculture?

Answer 1

Biocontrol is the process by which one living organism is used to control another. The agents which are used to control the pest using parasites and other predation are called biocontrol agents.

Eg : Predators, pathogens, bacteria,fungi and viruses.

Mechanism of action of Biocontrol agents.

There are mainly two mechanism.

Direct mechanism

Indirect mechanism

Direct mechanism is the direct killing or lysis of a pathogen by using Biocontrol agent.

Indirect mechanism is the process of exclusion of a plant pathogen as a result of activity, presence or product of a biocontrol agent.

Direct mechanism include :

Antibiosis and parasitism

Indirect mechanism include:

Competition and induced systematic resistance

Antibiotic mediated suppression:

Antibiotics are microbial toxins. At low concentrations antibiotics can kill other microorganisms. There are two types of antibiotics. They are volatile and non volatile antibiotics.

Volatile antibiotics include : hydrogen cyanide, aldehyde, alcohol,ketones, and sulphides.

Non volatile antibiotics include polyketide and heterocyclic compounds.

Parasitism

It is the process by using pathogen. Mycoparasitism is the process in which a parasitic fungus (hyperparasite) live as a parasite to another fungus ( hypoparasite).

Biocontrol agents grows towards the target and identify the receptor. Attachment of the fundi by cell wall degradation and finally penetration.

Competition:

Exclusion of pathogen by a Biocontrol agent by competing for space or nutrients

Induced systematic resistance (INR):

Resistance in plants to pathogen which is induced by the presence or products of a biocontrol agent.

Eg: Necrogenic pathogen which are applied on leaf.

Importance of molecular markers:

Molecular markers are used in agriculture to track desired traits. Markers can be identified by screening of traits.Markers which are linked to desired traits can be used during breeding to select varities of useful combination.