Low Cost Materials and Techniques for Production of Oyster (Pleurotus Ostreatus) Mushroom Spawn by Farmers

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Thuranira, S. G.
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Kenyatta University
Mushroom cultivation in Kenya is an emerging sector with great potential but its production is still low. In 1997, the world mushroom production was over 5 million tons. During this period, Kenya produced only 500 tons compared to its potential of 100,000 tons. The situation has not changed much with production estimated at 700 tons in 2010. The low production was due to supply of costly spawn which varied in quality and use of expensive sterilisation techniques. Again, spawn is multiplied in sorghum and other grains which are also used as food by man creating undue competition with producers and escalated spawn prices. Spawn is also produced far from farms which might interfere with mycelia development and compounds the cost of transport. This study was aimed at developing a cheap and simple method of sterilising substrate and cleaning the inoculation bench, and to identify an alternative substrate for multiplying spawn other than food grains. Grains of sorghum, wheat, millet, Sudan and Columbus were soaked overnight to soften, washed with tap water and excess water drained. Calcium carbonate was added to modify pH and fifty grams of each grain placed in plates. Sorghum grain was sterilised by autoclaving, pressure cooking or steaming before inoculation was done with Oyster spawn from Kabete. Similarly, grains were autoclaved and inoculated with spawn from Kabete, JKUAT, Juja community, Organic farm and Chiromo. During inoculation, the bench was cleaned by five different methods which include; open bench, hood with no supplementation, hood supplemented with alcohol spray, hood supplemented with spray and spirit lamp and laminar flow. The inoculated plates were immediately sealed and laid in a complete randomized design in the incubator at 25°C. The number of plates contaminated, type of fungal contaminants by colour and the rate of mycelia spread were recorded. GenStat 8th Edition was used to analyse the results and mean separation carried out at 95% significant level to find out if methods of sterilisation can achieve different results. Two way ANOV A statistics was carried out to establish whether methods of cleaning the bench and grain substrates were different. There was no significant difference between autoclaving and pressure cooking methods of sterilisation (P:s 0.05), but steaming was different from the other two. Contamination was 48.1 % in steamed samples, 39% in pressure cooked and 38% in autoclaved. Methods of cleaning the inoculation bench were also different though laminar flow was not different from hood supplemented with alcohol and spirit lamp (P:S 0.05). High contamination was recorded in open air bench (51 %) and least in laminar flow (33%). Methods of sterilisation and cleaning the bench did not affect mycelia spread. Grass grains were also not significantly different from food grains. Green fungal contaminant was the most common; over 80% and white fungal contam inant was lowest, 10%. The results have shown that pressure cooker can sterilise substrate, wood hood clean the inoculation bench and grass grains used as spawn carrier material. The study recommends that farmers grow sorghum grass to produce spawn and use the straw for mushroom cultivation.
Department of Microbiology, 81p. 2013, SB 353.5 .K4T48