Carbon substrate optimization for cultivation of pleurotus ostreatus and wild indigenous mushroom contherellus densifolius.

Abstract

The yield and quality of mushrooms are largely dependent on the substrate composition. Many Zimbabweans are venturing into mushroom farming with inadequate knowledge on substrate formulation for maximized yield.The yield and quality of mushrooms are largely dependent on the substrate composition. The main objective of the study was to determine the effect of different individual substrates and substrate combinations on the growth and sustainable development, perfomance during the cultivation of exotic P.ostreatus and wild Cantherellus in under constant conditions in a mushroom house. This study was carried out during the rainy seoson however these conditions do not have any implications on the results since we controlled the inernal environment of the mushroom.There is low published material related to oyster mushroom cultivation in Zimbabwe. Most of the substrates used in the literature review, highlighted substrates such as rice straw and palm kernek cake are agricutural wastes of crops not cultivated in Zimbabwe.Various substrate combinations in the ratio 1:1 used as treatments were cotton hulls -wheatstraw, cotton hulls-sawdust, cotton hullsmaizecobs, and cotton hulls-banana fronds. These substrates are commonly available in Zimbabwe. The combination producing the highest biological efficiency was used to cultivate wild indigenous C.densifolius. Fruition of C.densifolius was evaluated on hardwood sawdust and cotton hulls individually and in combination. Each combination weighed 1kg and was replicated 4 times.Compound substrates perfomed much better in terms of biological efficiency and spawn run compared to individual substrates. The highest biological efficiency (76%) and spawn run(17 days) for P.ostreatus were obtained from combining cotton hulls and sawdust followed by cotton hulls and maize cobs with biological efficiency of 50% and spawn run of 13 days. Consequently combining cotton hulls with a substrate that has a wide C:N ratio such as sawdust increases the biological efficiency as a result of the boost in the carbon component. Analysis in terms of economic return revealed that mushroom production was most profitable using cotton hulls and sawdust as substrate with a benefit-cost ratio of 5.7, followed by cotton hulls(4.2), cotton hulls-maizecobs(3.7), cotton hulls-banana fronds(2.4) and lastly cottonhulls-wheatstraw(2). The optimised substrate combination was then tested on the indigenous mushroom in an attempt to cultivate that wild and known to be naturally growing in the woods but instead under laboratory conditions. C. densifolius mycelia grew best on potato dextrose agar with a pH of 7 cultured in plates incubated in dark conditions, at room temperature (28 C), with no aeration. Mycelia of C.densifolius exhibited a higher rate of growth on Potato dextrose agar at a rate of 22.5mm/day obtained after 4 days, compared to Malt Extract agar that produced 12.9mm/day after 7days, to completely cover the petri plates and exhibited a tendency to change colour from white to green after 10 days of incubation. The phenomenon observed on the petri plates was deduced to be a spore print colouration. It took mycelia 6 days to completely cover Sorghum bicolor grains at 280C. Wheatstraw, banana fronds and maizecobs failed initiate fruiting. Cotton hulls produced green pinheads after 31 days of incubation. Sawdust and cotton hulls combination stimulated pinhead formation and maturation into fruiting bodies. The biological efficieny attained was 9% and the spawn run took 32 days. High yield and economic return can be obtained using sawdust and cotton hulls combination. The same combination can sustain growth and fruit formation of C.densifolius. We recommend use of this combination in the cultivation of P.ostreatus. We also recommend further studies into domestication of C.densifolius to increse the biological efficiency of C.densifolius.