PhD

Paddy straw mushroom (Volvariella spp.) stands third among the commercially cultivated mushrooms in India. Even then its production is very low, compared to the other mushrooms. ICAR has given very much importance in the research on this mushroom under the All India Co-ordinated Mushroom Improvement Project (AICMIP) because of its high nutritive and medicinal values. As a step in improving the biological efficiency of this mushroom a work was conducted in the Department of Plant Pathology, College Agriculture, Vellayani during the period 2000-2003. We could achieve some positive results which will pave way for further improvement and refinement of the techniques.

The cultural studies of the selected cultures were done and found that the most suitable medium for the growth of Volvariella was jack fruit kernel agar. The culture of Volvariella can be stored for the maximum period of 41 days in tapioca agar media, and 30-35 days in other tested media. A temperature level of 34 oC and light conditions namely blue, red, and yellow were equally efficient in enhancing the mycelial growth of Volvariella.

Paddy grain was found to be the most suitable substrate for the spawn production of Volvariella and due to lower percentage of contamination glucose drip bottle method was the most efficient method for spawn production. A temperature level of 34 oC and dark conditions favoured the spawn growth of Volvariella.

Hollow interior method of bed system was the best method in increasing the fruitbody formation of Volvariella. All the native isolates performed better than the isolate obtained from NRCM, Solan. Paddy straw and oil palm bunch wastes were equally effective in enhancing the fruiting of Volvariella. A temperature level of 32-36 oC, Relative Humidity of 80-85 %, and blue light conditions etc. favoured the fruiting of Volvariella. Green gram powder, wheat flour, and black gram powder were equally effective food supplements in promoting the fruiting of Volvariella. Chemical pasteurization was found to be the most efficient substrate pasteurization method. Casing of the bed with a substrate combination containing spent compost, coirpith compost and sand in the ratio 1:1:1 was found efficient one in increasing the fruiting. A substrate formulation containing paddy straw 50%, oil palm bunch waste 50 %, calcium carbonate 5%, gypsum 2.5%, rice bran 20% and urea 1% was found to be most suited for bed preparation with respect to yield. Calcium carbonate based substrate formulation was found to be the best growth medium than the talcum based substrate formulations.

In the strain improvement programme Gamma irradiation was used as source of irradiation and found that the culture irradiated at 0.5 KR levels showed maximum mycelial proliferation in the culture media as well as performed well with respect to yield, compared to the other irradiated isolates at different levels. Three successive progenies of irradiated isolate was evaluated and found that the sporocarp of successive progenies of irradiated isolate showed colour variation on the positive side. Improved cooking quality was also noticed in these successive generations. Single spore isolates of Volvariella out yielded multispore and tissue culture isolates. Hybridization has no significant role in the strain improvement programme of Volvariella.

The use of different coloured light traps in attracting the mushroom flies was studied and found that blue light was very efficient one in attracting them. A new effective way of trapping mushroom flies using hollow interior bed method was standardized. The effect of chemical pasteurization of the substrate in checking the weed mould infestation during spawn run have been proved.

Post harvest preservation technologies for improving the shelf life of Volvariella have been standardized. Among the packaging methods packing in poly propylene cover without air, and packing in perforated polythene cover were found to be the efficient methods to extend the post harvest storage life of Volvariella. Microwave cooking has been proved to be inefficient in the post harvest preservation. Among the drying methods, mushrooms dried in mushroom drier have shown superior qualities than the other methods of drying. In the case of blanching and preservation, blanched mushroom samples in high concentration preservatives and in brine solution at 2% concentration showed maximum shelf life.