<i>In vitro</i> Evaluation of Growth Inhibition of Some Common Soil Fungi by Selective and Non-selective Herbicides

Abstract

The indiscriminate and excessive use of herbicides being witnessed in recent times portends possible danger to environmental and human health. To gage the likely impacts of herbicides onfungal ecosystem services, the influence of three narrow [selective (atrazine, butachlor and 2,4-D)] and two broad [non-selective (glyphosate and paraquat)] spectrum herbicides at various concentrations of 0, 0.01, 0.1, 0.5 and 1% v/v on the radial mycelial extension growth, mycelial extension growth rate, percentage mycelial growth inhibition and minimum sporulation time of four common soil fungi, Aspergillus niger, A. flavus, Trichoderma viride and Penicillium sp. were investigated on PDA plates for a period of 96 h at 30 ± 2°C (room temperature). The radial mycelial extension growth of fungi decreased with increased concentrations of the herbicides except for T. viride where atrazine did not show any significant difference among all the concentrations tested (P≤0.05). The fastest mycelia extension growth rate for all fungi was recorded in Atrazine at the highest concentration tested, with T. viride being the fastest at 0.44 mm h-1. At 1% v/v, save for atrazine, all the herbicides inhibited at least 66% mycelial growth with 2,4-D showing a 100% inhibition. The minimum sporulation time for all fungi in the presence of the herbicides was 48 h. There was no sporulation in A. flavus and T. viride in presence of paraquat and 2,4-D above 0.1% v/v concentration within the 96 h of investigation. The results of this study suggest that indiscriminate and excessive use of herbicides could negatively affect ecosystem function.