Role of microorganisms in bio-control and biofertilizers

Introduction

As the organic farming is gaining its traction, bio-control is becoming more and more popular. Instead of using chemicals and chemical fertilizers, many biologically made pesticides and feeds can be used to reduce the adverse effects of the chemicals.  In a biocontrol mechanism, microbes can be killed by natural predators. Biocontrol also helps in bringing the balance through healthy predation. Let us discuss what are the biocontrol agents and the use of  microbes as the biological agents

Table of Contents

1. Introduction

2. Microbes as Biocontrol Agents

3. Microbes as biofertilizers

     3.1  Nitrogen-fixing Bio fertilisers

     3.2 Phosphorus  Solubilizing Bio fertilisers

     3.3 ​​​​​​Phosphorus mobilizers​

     3.4 Growth Promoting Rhizobacteria

Microbes as Biocontrol Agents

A number of biocontrol agents are being used. The use of ladybird and dragonflies help to keep a check against aphids and mosquitoes. Another example is the Bacillus thuringiensis, it can be introduced in order to control butterfly caterpillars in a farmland. Bacillus thuringiensis is sold in sachets as dried spores that can be mixed with water and sprayed onto vulnerable plants like brassicas and fruit trees. The spray sits on leaves is consumed by the insect larvae resulting in their death. The strain of Rhizobium soil bacterium has proved worthy in their ability to develop resistance against root-knot nematode in tomato plants. Caudovirales- a viral colony have effectively controlled columns of salmonella in wastewater. Caudovirales are bacteriophages that attack salmonella and destroy colonies of the pathogen. Fluorescent pseudomonads helps to discourage the growth of virulent bacteria among various plant’s root systems by producing antibiotics. Beauveria bassiana is a fungus demonstrated an ability to control mosquito populations that can cause malaria. The fungus targets and cause high mortality in mosquito larvae particularly in the third instar.

 

Microbes as biofertilizers

The need for this concept is growing as the chemical sprays have already destroyed the wealth of soil, water, air. Consumption of the crops sprayed by chemicals makes us ulnerable to many diseases. Biofertilizers are the preparations of strains of living cells or latent cells of efficient microbes help in enhancing the crop’s ability to uptake the nutrients. Biofertilizers combine along with the rhizosphere ( root system) when applied through seeds and soil.  The artificially multiplied strains of selected combinations of biofertilizers play a vital role in accelerating the microbial processes in soil. Biofertilizers are a cost-effective and renewable source of plant nutrients that replace the chemical fertilizers. Many microbes and their association with crop plants are being exploited in the production of biofertilizers. Some of the biofertilizers and their functional abilities are as follows

 

   Nitrogen-fixing Bio fertilisers

Sl no                   

Groups

Examples

1.

Free-living

Azotobacter, Beijerinkia, Clostridium, Klebsiella, Anabaena, Nostoc, 

2.

Symbiotic

Rhizobium, Frankia, Anabaena azollae

3.

Associative Symbiotic

Azospirillum

 

 Phosphorus  Solubilizing Bio fertilisers

Sl no

Groups

Examples

1.

Bacteria

Bacillus megaterium var. phosphaticum, Bacillus subtilis
Bacillus circulans, Pseudomonas striata

2.

Fungi

Penicillium sp, Aspergillus awamori

 

​​​​​​Phosphorus mobilizers​

Sl          no

Groups

Examples

1.

Arbuscular mycorrhiza

Glomus sp., Gigaspora sp., Acaulospora sp., 
Scutellospora sp. & Sclerocystis sp.

2.

Ectomycorrhiza

Laccaria sp., Pisolithus sp., Boletus sp., Amanita sp.

3.

Ericoid mycorrhizae

Pezizella ericae

4.

Orchid mycorrhiza

Rhizoctonia solani

 

Bio fertilisers as Micronutrients

Sl no

Groups

Examples

1.

Silicate and Zinc solubilizers

Bacillus sp.

 

Growth Promoting Rhizobacteria

Sl no

Groups

Examples

1.

Pseudomonas

Pseudomonas fluorescens

 



img-1

img-1

img-1

Course List