Types Suitable for cultivation
At present 3 mushrooms are being cultivated in India. These are : the white mushroom (Agaricus bisporus), the paddy-straw mushroom (Volvariella vovvacea) and the oyster mushroom (Pleurotus sajor-caju). Of these, A. bisporus is the most popular and economically sound to grow and is extensively cultivated throughout the world. However, due to its low temperature requirement, its cultivation is restricted to the cool climatic areas and to the winter in the plains of Northen India. In summer, the tropical paddy-straw mushroom is suitable for growing in most parts of India.
Even then it is less attractive commercially owing to very low yield per unit weight of the substrate and an extremely short shelf-life. But, as a kitchen-garden crop it is preferred because it is very delicious and nutritous.Oyster mushroom can grow at moderate temperature ranging from 220 to 280C. therefore, it is suitable for most of the places of India. It is a familiar item in the menu of most hotels in Bangalore where it is being grown commercially.In north India, the climate conditions prevailing during different seasons can be exploited for growing mushroom throughout the year. To this a year-wise production schedule is suggested :Mid-November to Mid-March : Agaricus bisporusFebruary to Mid-April : Pleurotus sajor-cajuMid-June to Mid-September : Volvariella volvaceaSeptember to November : Pleurotus sajor-caju
1. Selection of StrainsFor successful mushroom production, it is necessary for each grower to produce as economically and efficiently as possible the highest quality of mushrooms. This can be accomplished among other requirements, by selecting the best strains which should be high yielding , visually attractive, having desirable flavour, and resistance to adverse climate and pests and diseases. Presently, there are many strains of white, cream and brown varieties in cultivation. The brown variety is the natural mushroom and considered to be the most vigorous form. It tolerates and adverse conditions better than the white variety. A snow white mushroom first appeared amongst a bed of mushroom in the USA and ever since the variety has dominated the mushroom industry throughout the world, although it has a very high limited shelf-life. Where growing conditions tend to be on the dry side and humidity cannot be correctly controlled the brown mushroom should be grown. New superior strains are through selection, hybridization and induced mutations continually introduced by mushroom research laboratories and spawn makers. In India, S 11, S 649 and S791 are the good strains available. These strains were originally introduced from reowned commercial spawn makers, Somycel and darlington. Now these strains are well adapted in the Indian climate and are very popular with the growers.
2. Maintenance of Strains.Three methods are known by which strains can be propagate. these are multispore culture, tissue culture and mycelium transfer. By periodic subculturing of the mycelium on a suitable agar medium, the span strains can be kept for many years in a fairly good state. However, the frequent subculturing of the strain may result in its degeneration. Maintenence of strain by multisporous culture is only possible if new multispore cultures are compared with the original strain before the original multisporous culture would show much genetic variation. In the tissue culture, small pieces of fruit bodies are cut under sterile conditions and inoculated on a nutrient medium. Mycelium growing out of these tissue can provide the starting point for subsequent spawn production. However, it is commonly observed that tissue cultures often give lower yields than the original cultures. Of these 3 methods, mycelium transfer is most reliable but it is essential that the performance of the mycelium is continually checked in order to detect any degeneration-like slow-growing matted mycelium or fluffy mycelium with abnormal growth rate.
The propogating material used by the mushroom growers for planting beds is called spawn. The spawn is equivalent to vegetative seed of higher plant. Quality of spawn is basic for the successful mushroom cultivation.At present, the pure culture spawn has been the basis of modern spawn production units all over the world. The manufacture of the pure culture spawn is done under scientifically controlled conditions which demand a standard of hygiene as in a hospital operation theatre. Equipment and substrate used for spawn are autoclaved and filtered air is passed during the inocluation ensures complete freedom from contamination.(a) Manure spawnBoth composted horse-dung or synthetic compost may be used. The composted manure is thoroughly washed to remove such substance in compost which retard growth. The excess water is squeezed out and moisture content adjusted to 60%. The manure is packed in half-litre milk bottles or heat-resistant polypropylene bags os suitable size. The bottles or bags plugged with non-absorbant cotton-wool and sterlized in an autoculave at 1210C for 2 hr or on 2 consecutive days for an hour each. They are then inoculated with a large bit of agar-containing mycelium and incubated at 220-240C in a dark place. the spawn can be used to inoculate fresh bottles or bags to obtain the second generation spawn.(b) Grain spawnTen kilograms of wheat grains are boiled for 15 min in 15 litres of water and then allowed to soak for another 15 min without heating. the excess water is drained off and the grains are colled in sieves. Turn the grains several times with a spoon for quick cooling. The colled grains, are mixed with calcium carbonate. the gypsum (CaSO4.2H2O) and 30 g fo calcium carbonate. The gypsum prevents the grains from sticking together and calcium carbonate is necessary to correct the pH. the prepared grains are filled into half-litre milk bottles or polypropylene bags (at the rate of 150-200 g per bottle or bag) and autocalved for 2 hr at 1210C. After sterlization, the material should have a pH value of 6.5 to 6.7. the bottles are inoculated with grains spawn or with bits of agar medium colonized with mycelium and incubated at 220-240C in a dark place. the mycelium completely permeates the grains in about 2 weeks. Other grains like sorghum and pearlmillet can also be used for spawn making.(c)Perlite spawnThis was developed by Lemke (1971). Perlite is a mineral which expands at temperature more than 10000C. The ingredients, of the spawn are : Perlite (1,450 g), wheat-bran (1,650 g), gypsum (200 g), calcium carbonate (50 g), and water (665 cc). The gredients are mixed, filled in bottles and sterlized. Thereafter, the process is the same as for grain spawn. Perlite spawn is easy to disperse and can be produced at a cheaper cost. This spawn can be stored for a long time.
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