In this course you will learn introductory terms and concepts related to biofertilizers and their production
- Course Structure: Contents and Assessment Pattern
- General Instructions for the course
- Module 1
- Lesson 1: Introduction to Biofertilizer Production
- Quiz on: Lesson 1: Introduction to Biofertilizer Production
- Lesson 2: Nitrogen Fixing Microorganisms
- Lesson 3: Video Demonstration- Biofertilizer production using Nitrogen fixing Microorganisms
- Quiz on Lessons 2 and 3: Nitrogen Fixing Microorganisms and Biofertilizer Production
- Module 1: INQUIRY BASED LEARNING (IBL) Problem I
- Project component 1
- Module 2
- Lesson: Phosphate Solubilising Microorganisms
- Quiz on: Lesson: Phosphate Solubilising Microorganisms
- Module 2: Inquiry Based Learning (IBL) Problem II
- Project component 2
- Module 3
- Lesson: Indole-3-Acetic Acid Producing Microorganisms
- Quiz on Lesson: Indole-3-Acetic Acid Producing Microorganisms
- Module 3: Inquiry Based Learning (IBL) Problem III
- Project component 3
- Module 4
- Lesson: Siderophore Producing Microorganisms
- Quiz on Lesson: Siderophore Producing Microorganisms
- Module 4: Inquiry Based Learning (IBL) Problem IV
- Project component 4
Lesson: Indole-3-Acetic Acid Producing Microorganisms
What is IAA?
- IAA is the main auxin (phytohormone) in plants. It regulates plant growth and developmental processes such as cell division and elongation, tissue differentiation. It governs root elongation and branching [1,2]. It regulates response to pathogens.
- In addition to plants, Indole-3-Acetic Acid is also produced by microorganisms found in rhizospheric soil and by endophytes of plants.
- Structure of IAA can be seen at the following link: https://pubchem.ncbi.nlm.nih.gov/compound/Indole-3-acetic-acid#section=2D-Structure
What is the importance of IAA Producing Microorganisms ?
- If such organisms are included as components of biofertilizers, application of such biofertilizers to seeds or agricultural soil can enhance the growth of the plants/ crops.
What are the examples of Indole-3-Acetic Acid Producing Microorganisms?
- Indole-3-Acetic Acid ProducingMicroorganisms are of the following types:
- Bacteria: e.g. Bacillus sp., Pseudomonas sp., Azotobacter sp. and Rhizobium sp.
- Some plant pathogenic fungi produce IAA: e.g. Fusariun oxysporum, Colletotrichum gloeosporioides, Pleurotus ostreatusand Nectria pterospermi;
- Some mycorrhizal fungi and yeasts also produce IAA.
On which nutrient media would you grow them?
- They can be grown on various media but their activity is detected [1,2] using:
- Nutrient broth supplemented with 5 mg/ mL tryptophan.
What is the composition of Nutrient broth medium ?
- Composition of Nutrient broth medium :
- Ingredients Gms / Litre: Peptone 10.0, Beef extract 10.0, Sodium chloride 5.0 The pH of the medium is adjusted to 7.0-7.2.
- For Nutrient agar, Agar-agar 25 g/ L is added to the medium before autoclaving it.
- Composition of Nutrient broth medium :
How do you sterilize these media?
- Autoclave the medium at 15 PSI (ie lbs/ in2), at 121.6°C for 15-20 min. Cool the medium to room temperature before use. Pour agar containing media into sterile petri plates when they are moderately hot ie 55-60°C. Allow the media to solidify or set.
How would you detect and estimate IAA produced ?
Production of IAA is determined by colorimetric method of Gordon & Weber. The cultures are inoculated in Nutrient broth supplemented with 5 mg/ mL tryptophan, incubated at 30 °C for 24 h under shaking conditions. The broth is then centrifuged at 10,000 rpm for 10 min at 4°C to get cell free supernatant. Two mL of Salkowski’s reagent (2 ml 0.5M FeCl3 added to 98 ml 35% perchloric acid) is added to 1mL of cell free supernatant thus obtained. It is incubated in the dark for 30 min at room temperature. Development of pink color indicates production of IAA. The intensity of pink color that develops is measured at a wavelength of 540 nm and the concentration of IAA produced is estimated by comparison with the standard dose response curve for IAA (10 μg/ mL to 100 μg/ mL) estimation by the method of Gordon & Weber.
Since Salkowski reagent also detects and gives a pink color with indole, indole-3-butyric acid and skatole, the production of IAA can be confirmed by Thin Layer Chromatography (TLC).
- Desai, P & Sayyed, Riyaz (2011). Antifungal And Phytohormone Production Ability Of Plant Growth Promoting Rhizobacteria Associated With The Rhizosphere Of Sugarcane. Journal of Microbial World. 13:112-116.
- Sneha Ogale, Karan Singh Yadav and Shrutika Navale. Screening of endophytic bacteria from the pharmacologically important medicinal plant Gloriosa superbafor their multiple plant growth promoting properties. The Pharma Innovation. 2018; 7(1): 208-214.
- Mohite. ‘Isolation and characterization of indole acetic acid (IAA) producing bacteria from rhizospheric soil and its effect on plant growth’. Journal of Soil Science and Plant Nutrition , 2013, 13(3), 638-649.
- Ogale S., Kulkarni A., Nichit S.and Shah D. ‘Screening Of Endophytes Of Gloriosa superbaFor Their Plant Growth Promoting Potential And Optimization Of Indole-3-Acetic Acid Production. World Journal of Pharmaceutical Research’. 2018. 7 (4): 145-155.
- Gordon SA and Weber RP. Colorimetric Estimation of Indole acetic Acid. Plant Physiology, 1951; 26(1): 192-195.