Pranab Dutta and BC Das
Biocontrol offers safe, inexpensive and environmentally friendly management of plant diseases and avoids or minimizes the use of harmful fungicides. In the biological control of plant diseases, fungal antagonists like Trichoderma spp. Are widely used for the control of several soil-borne diseases and also have the added benefit of a growth-promoting effect. Numerous commercial formulations in solid form based on these antagonists have been developed throughout the world.
Trichoderma is a genus of asexually reproducing fungi found in almost all temperate and tropical soils. The genus is a potent, fast growing saprophyte, prolific spore producers and potent antibiotic producers. These properties make these fungi ecologically diverse and can be used to produce a wide range of products of commercial and ecological interest. Trichoderma has become a model biocontrol agent in plant disease management outside of IDM due to the following characters:
· Produces high yield, high quality conidia biomass.
· Possess a rhizosphere skill.
· Ability to thrive in a wide range of stressful conditions.
· Have a mycoparasitic capacity against a large number of soil-borne pathogens.
· Stimulates plant resistance and defense mechanism.
· Compatible with a large number of parasites.
· Easy to multiply in mass.
· The final product has a shelf life of more than 6 months.
MODE OF ACTION
· Mycoparasitism by production of enzymes and coiling.
· Antibiosis by production of antibiotics.
· Competition for food advertising space.
TRICHODERMA STRAIN SELECTION
Over the past 19 years, we have searched for a suitable biological control agent to use as a seed and soil treatment agent, we have successfully identified a strain of T. harzianum (DPP-105). With this, a “Biogaurd” formulation was formulated to meet the demand of farmers.
The various processes involved in the production of “Biogaurd” are
Selection of culture medium
Mass growth and multiplication
Harvesting and drying
· Scaling and
Three methods viz. solid fermentation, liquid fermentation and deep tank fermentation technology are followed for the multiplication of Trichoderma. Among these solids, fermentation is easy, popular and widely used by farmers.
SOLID FERMENTATION PROCESS
Improved selective media have been developed for the cultivation of Trichoderma spp. Solid media are prepared comprising readily available organic materials such as wheat bran, sawdust, grain bran, wheat straw, rice straw, sorghum grain, banana leaves, skin peeled banana, farmyard manure (FYM). Currently, FYM and wheat bran sawdust are widely used to produce biological control agents against T. harzainum and T. viride. Well-decomposed powdered FYM mixed with 1% peptone and 1/2 part water is autoclaved at 30 pounds pressure for 1 hour intermittently for 2 times and heaped in a clean, shaded area. The stock culture of Trichoderma spp. Multiplied on potato agar medium (PDA) for 15 days inoculated under aseptic conditions, 500 ml of homogeneous suspension of spores prepared in a mixer are used for 10 kg of FYM. The piles are then covered with polythene sheets (to prevent moisture loss) for 30 days. The piles are thoroughly mixed at a 7 day interval. After 30 days of incubation this preparation is ready to be applied.
This process involves the production of large numbers of conidia primarily for seed treatment, soil application and foliar spraying. The liquid bioformulation based on Trichoderma developed at the AAU, i.e. Org-Trichojal with a shelf life of 16 months, has been shown to be very effective in farmers’ fields for the management of pathogens of plants and improve plant growth parameter and plant defense metabolite. The product was marketed by a private entrepreneur.
DEEP TANK LIQUID FERMENTATION TECHNOLOGY
This involves the massive production of mushrooms. In this technique Trichoderma spp. Are mass cultured in inexpensive commercially available ingredients (molasses and brewer’s yeast). Rapid mass production of antagonists for seed treatment formulation, mainly used deep tank liquid fermentation.
GROWTH AND MASS MULTIPLICATION:
The fermentation medium used to cultivate and mass multiply Trichoderma spp. Consists of molasses (30 kg) + brewer’s yeast (5 g) + 1 liter of water (the fermentation medium of the above concentrations is used. The procedure for the mass production of Trichoderma spp. is given below below:
Autoclave the starter and the fermented medium for 1 hour
Inoculate the starter medium with an effective strain of Trichoderma and shake on a rotary shaker
Inoculate the fermented media with the starting inoculum and supply regularly for 10 to 15 days by shaking/bubbling
Strain through cotton muslin using a funnel
Air dry or freeze dry the mat for 3 days, then grind it into powder, it contains mycelium and chlamydospores.
The powder is diluted with different diluents and used as dusts, granules, tablets, wettable powders, emulsifiable concentration
The product is viable for 6 months if stored at 50°C and 3 months if stored at 200°C
The maximum biomass is generally obtained after 15 days of inoculation.
Different formulations are available and prepared for use as shown below.
1. Powder formulation: It is made by mixing the biomass of the fermenter with talcum powder as carrier.
2. Encapsulation in an organic polymer such as sodium alginate.
3. Granulation of biomass and bran with sodium alginate.
(To be continued)