Abilities of Some Fungi to Use Paraquat Dichloride and Glyphosate Herbicides for In Vitro Growth

Abstract

Herbicides for weed control end up largely in the soil where they may be disadvantageous to the biotic components and pose health hazards if consumed in crops. Paraquat dichloride and Glyphosate were tested singly and in combination at the same concentration in liquid culture for degradation at 30°C for 91 days using seventeen filamentous fungi from agricultural soils. Controls did not contain herbicides.  Paraquat was utilized for mycelium production better than glyphosate. Trichoderma harzianum and Curvularia lunata used the two herbicides best singly and as mixture.  Trichoderma sp. (TrS18) grew well in single herbicides but not in the mixture. Aspergillus sydowii and Stachybotryis sp. (SSF) were inhibited by single herbicides and mixture producing 130mg/193mg and 63mg/160mg mycelium in paraquat/control. They also produced 90mg/193mg and 87mg/160mg in glyphosate/control, while in mixture/control, mycelia were 117mg/193mg and 90mg/160mg respectively for the two fungi. Six other fungal species had good growth but not as much as the Trichoderma species and C. lunata in either or both herbicides singly or in their mixture. Seven species including Rhizopus sp. (RhS18), Rhizopus microsporus, and Mucor sp. ((McS18) did not grow well.  Aspergillus sp. (APS) was inhibited by single herbicide and mixture producing 23mg/33mg, 27mg/33mg; and 17mg/33mg in paraquat/control, glyphosate/control; and mixture/control respectively. Zygorhynchus sp. (ZST) grew well on both herbicides singly, utilizing glyphosate better than paraquat. Diplodia sp. (DST) grew more in paraquat than in glyphosate but the converse was the result for Stachybotryis sp. (SSF). A. sydowii reduced paraquat and glyphosate concentrations in culture media by 7.17% and 10.90% respectively. T. harzianum reduced paraquat and glyphosate in medium by 13.23% and 12.62% respectively. These results imply that some of the fungi could be useful in bioremediation of soils contaminated by either or both herbicides.