Many fungi have been reported to enhance the plant responses and degradation of several persistent pollutants in soils. In this study, five dominant fungi strains were identified from a pesticides polluted soil in Nigeria and screened for the expression of phosphoesterase (opd and mpd) and catechol 1, 2-dioxygenase (afk2 and afk4) genes using Reverse Transcriptase-PCR technique. Their rhizosphere interaction with plant (Panicum maximum) was further studied for the degradation of 2, 2 Dichlorovinyl dimethyl phosphate (dichlorvos). Fungal strains were mixed with Spent Mushroom Compost (SMC) of Pleurotus ostreatus in 1:100 w/w and then applied to a sterilized pesticide polluted soil (5 kg) at increasing concentrations of 10, 20, 30 and 40% with two controls (plant only and fungi-SMC mixture only). Degradation efficiency (DE), degradation rate (K1) and half-life (t1/2) of dichlorvos was calculated in each treatment after 90-day of planting. All the strains were registered at NCBI gene-bank with accession numbers KY693969, KY488464, KY488465, KY693971 and KY693972: they all possess the tested genes although mpd and opd were over-expressed in all the strains while afk2 and afk4 were moderately expressed. The plant-fungi-SMC interaction synergistically sped-up dichlorvos degradation rate in less time period, appreciable loss of dichlorvos at 72.23 and 82.70% DE were observed in 30 and 40% treatments respectively as compared to controls 1 and 2 having 62.20 ± 3.07 and 62.33 ± 4.69% DE respectively. In the same way, the 40% treatment gave the best k1 and t1/2 of 1.755 and 0.40 ± 0.02/day respectively.
Keywords: Degradation rate; Dichlorvos; Fungi; Gene expression; Plant; Spent mushroom compost.
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