MASS MULTIPLICATION OF ARBUSCULAR MYCORRHIZAE (AM) FUNGI

MASS MULTIPLICATION OF ARBUSCULAR MYCORRHIZAE (AM) FUNGI

• The commercial utilization of AM fungi has become difficult because of the Obligate symbiotic nature and difficulty in culturing on laboratory media.
• Production of AM fungal inoculum has evolved from the original use of infested field soils to the current practice of using Pot culture inoculum derived from the surface disinfected spores of single AM fungus on a host plant grown in sterilized culture medium.
• Several researches in different parts of the world resulted in different methods of production of AM fungal inoculum as soil based culture as well as carrier based inoculum.
• Root organ culture is being used for the production of soil less culture.
• As a carrier based inoculum, Pot culture is widely adopted method for production. The AM inoculum was prepared by using sterilized soil and wide array of host crops were used as host. The sterilization process is a cumbersome one the inert materials such as vermiculite, perlite, montmorillonite clay etc. are utilized for the production.

Mother Culture

• Mother culture can be produced from efficient spores using funnel techniques as well as multiplication in small sized pots.
• Three to four cycles will be made for developing the Mother culture.
• Mother culture should have 100 % root colonization and the minimum of 8 -10 spores per gram of the inoculum.
• Mother culture can also be maintained in Maize (Zea mays L.) roots continuously.

Steps for Mass production of AM Fungi

• Form a trench (1 m × 1 m × 30 cm) is and line with black Polythene sheet to use this as a plant growth tub.
• Mix 50 kg of Vermiculite and 5 kg of sterilized Soil and pack in the trench up to a height of 20 cm.
• Spread 2 kg of AM inoculum (Mother culture) below the surface (2 - 5 cm) of Vermiculite.
• Sow with surface sterilized Maize seeds (5 % Sodium hypochlorite for 2 minutes).
• Apply 2 g Urea, 2 g Super phosphate and 1 g Muriate of Potash for each trench at the time of Sowing seeds. Further apply 10 g of Urea twice on 30^th and 45^th days after sowing for each trench.
• Apply 1 g of micronutrient mixture when there will be a symptom for deficiency.
• Test the quality of the inoculum by estimating the AM fungal spore colonization in plant root samples on 30^th and 45^th day.
• Grow the stock plants for 60 days (8 weeks).
• Pull out the plants and cut the roots into small pieces.
• Mix the roots thoroughly with Vermiculite in the trench.
• The inoculum produced consists of a mixture of Vermiculite, Spores, Pieces of hyphae and Infected root pieces.
• Within 60 days 55 kg of AM inoculum could be produced from 1 sq m area.  This inoculum will be sufficient to treat 550 m² nursery area having 11,000 seedlings.
• Periodical sampling of the AM fungal inoculums should be taken for Root colonization and Spore load.

Figure – 1: Mass production of AM Fungi

Preservation and Precautions for AM Fungal Biofertilizer

• Mycorrhizal biofertilizer can be kept under shade at room temperature. Normally AM fungi can live for 1 - 5 years, depending on the species.
• Avoid using AM Mycorrhizal biofertilizer on plants with root rot or stem rot. Mycorrhizal biofertilizer is more useful when applied prior the infection.
• Avoid using AM Mycorrhiza biofertilizer with some chemical products such as Fosetyl, Metalazyl and Metalaxyl mancozeb since these substances can inhibit growth of AM Mycorrhizal fungi.