Comparative Evaluation of Three Tropical Grass Substrates for Oyster Mushroom (Pleurotus ostreatus var. florida) Cultivation in Southern Nigeria

Identification of cost-effective lignocellulosic substrates is fundamental to expanding small-holder oyster mushroom production in tropical Africa. This study evaluated three tropical grass species — Eleusine indica, Chrysopogon zizanioides and Chromolaena odorata — as cultivation substrates for Pleurotus ostreatus var. florida. Six C. odorata replicates were started; one (16.7%) was lost to bacterial contamination, leaving n = 7, 6 and 5 respectively. Mycelial colonisation, primordium initiation, fruit body number, fresh weight yield and contamination incidence were recorded over two flushes. No casing layer was applied; fructification was induced by cover removal and misting, consistent with P. ostreatus biology. E. indica demonstrated superior performance: full colonisation 12.3 ± 0.8 days; primordium initiation 3.4 ± 0.3 days after cover removal; 104 total fruit bodies (183.9 g); mean 14.9 ± 2.1 fruit bodies per replicate (95% CI: 12.4–17.4). C. zizanioides: 14.2 ± 1.0 days; 3.8 ± 0.4 days; 75 fruit bodies (163.0 g); 12.5 ± 1.8 per replicate. C. odorata (n = 5): 16.5 ± 1.5 days; 4.6 ± 0.5 days; 31 fruit bodies (58.9 g); 5.2 ± 0.9 per replicate. ANOVA confirmed significant treatment effects on fruit body number (F(2,16) = 8.45, p = 0.0035, η² = 0.514) and fresh weight (F(2,16) = 7.32, p = 0.0061, η² = 0.478). Corrected estimated biological efficiency — calculated using 10–15% dry matter after air-drying (50–75 g dry per 500 g wet bag) — was approximately 35–53% for E. indica, 36–54% for C. zizanioides and 16–24% for C. odorata; these replace erroneous original estimates based on an incorrect 20% dry matter assumption, and are explicitly approximate, as dry weights were not directly measured. E. indica is the optimal substrate among the three for small-scale P. ostreatus cultivation in the evaluated tropical setting. Submitted to the African Journal of Biotechnology, March 2026. Currently under peer review.