Phytotoxicity assay of diesel fuel-spiked substrates remediated with Pleurotus tuberregium using Zea mays

Summary: The remediation of soil contaminated with petroleum based compounds by white rot fungi is well documented. In this study the ability of diesel fuel contaminated soils treated with the fungus Pleurotus tuber-regium to support plant growth was tested. Pleurotus tuber-regium was grown in different levels (2.50, 5.00, 10.00% and control- no fungus for each level of contamination) of diesel fuel contaminated soil and sawdust. The removal of petroleum hydrocarbons was highest in the 5.00% level of contamination where 55.53% of the petroleum hydrocarbons were removed. The least reduction in hydrocarbons was in the 10.00% level of contamination where only 35.53% of the hydrocarbons were removed. After the remediation the toxicity of the soils were tested by growing Zea mays in the treated soils. There was reduction in the toxicity of the soils treated with Pleurotus tuber-regium. Germination of the seeds of the test plant in treated 2.50 and 5.00% diesel fuel contaminated substrates was higher than that in the control. Germination of seeds in the 10.00% diesel fuel contaminated substrates was less than that in the control. The continued growth of the plant in the treated soils however showed no significant difference between them and the control using leaf area, plant height, fresh weight, dry weight and root length indices. The formation of lateral roots was however adversely affected in the treated 10.00% contaminated soil only substrate. The fungus was able to reduce the toxicity of diesel fuel contaminated substrates when compared with control in which there was no remediation. Industrial relevance: Nigeria is an oil producing country with heavy or high reliance on diesel fuel for use in cars and electric power generating sets. The transportation of diesel fuel is by tankers and pipelines. There have been cases of spills which has adverse effect on the environment. The study aims to solve the process of amelioration of the environment biologically by the use of white rot fungi which is more environments friendly and cheaper for a developing country like Nigeria. The assessment of the improvement of contaminated soil by the fungus is tested by using Zea mays easily obtained and cheaper too. The fungus Pleurotus tuber-regium is indigenous to Nigeria and can be used for the remediation of diesel fuel contaminated soils or substrates.