What is Spawn ?
Spawn means the vegetative mycelial network of a mushroom developed after the germination of one or more than one fungal spore (s) grown on a convenient medium.
SPAWN PRODUCTION OF MUSHROOMS
◦ Preparation of master culture or mother spawn is carried out under completely sterile conditions.
◦ Pure culture raised either from tissue or spores is inoculated in a suitable substratum (wheat, sorghum or rye) which provides food to the mycelium. Ten kg. of wheat grains are boiled in 15 liters of water for 20 minutes. Water is then drained off and the grains are put over the sieve or on a wire mesh tray for 8-10 hours to dry or remove excess of water. Grains are now mixed with gypsum (calcium sulphate) and chalk powder (calcium carbonate) at the rate of 2% and 0.5%, respectively on dry weight basis. 10 Kg of dry wheat grains will require about 200g gypsum and 50g chalk powder.
This will help to check the pH of the medium and also prevent sticking of grains with one another. The grains are filled into half or one liter glucose bottles or PP bags which are plugged with nonabsorbent cotton and sterilized at 22 lbp.s.i pressure for 1.5-2 hours. Sterilized bottles are allowed to cool down overnight. Next day bottles are inoculated with the bits of agar medium colonized with the mycelium of pure culture.
Inoculated bottles are incubated at 25± 1oC. After 7 days of inoculation, bottles are shaken vigorously so that mycelial threads are broken and become well mixed with the grains. Two week after inoculation, the bottles are ready as stock culture for further multiplication of spawn. One bottle of stock culture or master culture or mother spawn is sufficient to multiply 30-40 grain bottles or pp bags.
MULTIPLICATION OF SPAWN FROM STOCK / MASTER CULTURE
➢ Master spawn or master culture bottles / bags are further used for inoculation of large number of other grain bags / bottles prepared by the same technique and resultant is the commercial spawn.
➢ Generally few mycelial coated grains from one master culture bottle / bag will be inoculated into 30– 40 grain bags aseptically in front of the HEPA (High Efficiency Particulate Air ) filters of a Laminar flow and then incubated in a room at 25 ± 1 ° C for12-15 days. The commercial spawn thus prepared is used for inoculating the compost beds as seed.
PRECAUTIONS TO BE OBSERVED :
❑ Avoid overcooking of grains as it may lead to splitting of grains.
❑ Don’t dry the cooked grains on the floor. Always dry over hessian cloth spread ona raised platform or on a wire mesh tray .
❑ Use only recommended dose of CaCO3 for mixing with the cooked grains. Mixing over dose reduces the fungal growth in the inoculated bags.
❑ Avoid further sub culturing of the second generation spawn. This leads to loss of vigour of the spawn which again leads to reduced yield.
❑ Repeated sub culturing leads to complete loss of vigour. In such cases the fungal growth may be noted in the compost beds but buttoning may be completely arrested.
CHARACTERS OF GOOD SPAWN
➢ There should be proper coating of the mycelium around every grain used as substrate for spawn.
➢ The growth of the mycelium in the spawn bottles should not be cottony or fluffy type but it should be strandy .
➢ The growth of fresh spawn is more or less white. Brown coloration develops as spawn grows.
➢ There should not be any slimy growth in the spawn bottles which is an indication of bacterial contamination.
➢ There should not be any greenish or blackish spot in the spawn bottles. Such type of spots indicate that the spawn is contaminated with molds.