Unit 2: Cultivation Techniques

Infrastructure

This includes all the basic equipment and facilities needed for mushroom cultivation, from small-scale home growing to a larger operation.

Growing Structures

• Mushroom Unit (Thatched House): A low-cost, traditional structure made from bamboo and thatch (like paddy straw). It helps maintain humidity and protects from direct sunlight and rain.
• Culture Rack: Shelves (usually made of bamboo or wood) inside the mushroom house to hold the mushroom beds or polybags in tiers, maximizing the use of space.

Substrates

• Locally Available Substrates: The bulk organic material that the mushroom mycelium will grow on and use as food. Common examples are paddy straw, wheat straw, sugarcane bagasse, sawdust, and banana leaves.

Equipment for Preparation and Growing

• Low-cost Stove / Drum: Used for boiling water and pasteurizing (partially sterilizing) the substrate (e.g., boiling straw to kill competitor molds).
• Sieves: For draining water from the substrate after boiling.
• Vessels: Large pots or tubs for soaking and boiling the substrate.
• Polythene Bag: The most common container for growing oyster mushrooms. The substrate and spawn are packed inside.
• Small polythene bag: Can be used for preparing or storing spawn.
• Tray: Used for growing button mushrooms (Agaricus) on compost beds.
• Water Sprayer: Essential for maintaining high humidity (80-90%) in the mushroom house by misting the air and bags.

Tools for Inoculation

• Inoculation Hook / Inoculation Loop: Tools used in a sterile lab environment to transfer the pure fungal culture (mycelium) from one petri dish or test tube to another, or to the spawn substrate. They are sterilized in a flame before each use.

Pure-culture: Medium and Sterilization

Pure Culture

A pure culture is a laboratory culture that contains only a single, known species of fungus (e.g., Pleurotus ostreatus), free from all contaminants like bacteria or other molds.

Starting with a pure culture is essential for successful cultivation. If you start with a contaminated culture, the contaminants will out-compete the mushroom, and the crop will fail.

Medium

A medium (or growth medium) is the nutrient-rich substance used in the laboratory to grow the pure culture. A common medium for fungi is Potato Dextrose Agar (PDA).

• Potato: Provides starch and minerals.
• Dextrose (Glucose): Provides a simple sugar for energy.
• Agar: A gelatin-like substance from seaweed, used to make the medium solid (like in a Petri dish).

Sterilization

Sterilization is the process of killing all forms of life and their spores (e.g., bacteria, fungi, endospores) from the medium or equipment.

This is a critical step. The nutrient-rich medium will grow contaminants much faster than the mushroom mycelium if it is not sterile.

• Method: The medium (e.g., PDA in a flask) and glassware are sterilized using an Autoclave.
• Parameters: The autoclave uses high-pressure steam at 121°C and 15 psi (pounds per square inch) pressure for 15-20 minutes. This is the only reliable way to kill heat-resistant bacterial endospores.
• Aseptic Technique: After sterilization, all transfers (e.rowing the pure culture) must be done using aseptic technique (e.g., using a flame-sterilized loop, working near a flame or in a Laminar Air Flow hood) to prevent re-contamination.

Preparation of Spawn and Multiplication

What is Spawn?

Spawn is the "seed" for mushroom cultivation. It is a substrate (like grain or sawdust) that has been completely colonized by the pure mushroom mycelium.

Instead of trying to grow the mushroom from microscopic spores, farmers use spawn, which is already a vigorous, established network of mycelium. This gives the mushroom a huge head start against any potential contaminants.

Preparation of Spawn

The most common type is grain spawn.

1. Select Grains: Wheat, rye, sorghum (jowar), or millet are commonly used.
2. Prepare Grains: The grains are washed and boiled in water until they are hydrated (swollen) but not split.
3. Dry and Mix: The grains are drained well. Chalk (calcium carbonate) is often added to balance the pH and prevent grains from sticking.
4. Bag and Sterilize: The prepared grains are filled into heat-resistant polypropylene bags or glass bottles, plugged, and then sterilized in an autoclave (121°C, 15 psi, for 1-2 hours) to kill all contaminants.
5. Inoculation: Once the sterile grain has cooled, a small piece of the pure culture (from the PDA dish) is transferred aseptically into the bag of grain.
6. Incubation: The bags are sealed and left in a dark, clean room for 2-4 weeks. The mycelium will grow out from the agar piece and spread, completely covering all the grains in a white, fluffy mass. This final product is the spawn.

Multiplication

Spawn can be "multiplied" to create more spawn. Instead of using the PDA culture (which is slow), a spawn-maker can simply take a handful of the fully colonized grain spawn and transfer it to a new, sterile bag of grains. This is called a Grain-to-Grain (G2G) transfer and is much faster, as the mycelium is already adapted to growing on grain.