The effect of wheat straw leachate on growth of oyster mushroom (Pleurotus ostreatus) spawn

Abstract

Wheat straw (Triticum aestivum – Duzi) is known for its growth inhibitor in both field and in vitro experiments. The roots of lettuce and wheat seedlings were particularly inhibited when incubated with leachate of wheat straw. In South Africa, mushroom industry is the only industry that directly converts straw into a protein source for human consumption. Therefore, the objectives of the study was to assess the potential growth inhibition of wheat straw extracts on seed germination and on growth of oyster mushroom; and to investigate (potassium, calcium and magnesium) salt concentrations capable of growth inhibition on stored wheat straw. Two sets of experiments were conducted in a completely randomized design with treatments being dilution levels of wheat straw leachate, replicated four times. The dilution levels used were undiluted leachate (100%); 75% leachate + 25% dH₂0; 50% leachate + 50% dH₂0; 25% leachate + 75% dH₂0 and dH₂0 (control). Wheat straw extracts were collected from recently dried wheat straw, and from wheat straw stored for 3 months or 6 months of storage for the lettuce trial whereas for oyster mushrooms spawn, extracts were collected from recently dried or wheat straw stored for 6 months under shed house temperature. Distilled water (dH₂0) resulted in high germination rate of lettuce seeds for cycle 1, 2 and 3. Undiluted leachate inhibited germination of lettuce seeds by 100% due to the freshness of the wheat straw. Wheat straw stored for 3 months and 6 months resulted in seed germination after 24 hours. Mycelial growth was seen after 24 to 96 hours from leachate of recently dried wheat straw in all dilutions. Therefore, farmers can be advised to store wheat straw to break chemicals capable of inhibiting growth of oyster mushrooms.

Keywords: Dilutions, germination, inhibition, mycelia, storage.