Effect of herbicides on cellulolytic activity of soil micromycetes

Abstract

This study examines the effect of different rates of 2,4-D and Paraquat herbicides under in vitro conditions on the cellulolytic activity of 20 strains of cellulolytic fungi isolated from the chernozem soil taken from Mount Fruška Gora. Results showed that high rates of 2,4-D (60, 120 and 240 g/ml) inhibited the cellulolytic activity of Fusarium aquaeductum var. dimerum, Fusarium solani var. argillaceum, Aspergillus candidus, Aspergillus ustus and Fusarium sp. (L-7). Lower rates of 2,4-D (30 and 60 g/ml) stimulated the cellulolytic activity of most Penicillium species. Paraquat exhibited higher toxicity to cellulolytic micromycetes and their cellulose degradation ability. Its inhibitory effect was observed at rates as low as those above 3μg/mL. Inhibition increased with increasing rates of the herbicide, with only eight fungi retaining at least some degree of cellulose degradation ability at 24 μg/mL Paraquat. Most species of the genera Aspergillus and Penicillium showed high sensitivity to Paraquat at rates as low as 6 μg/mL. At 24 μg/mL, none of them had the ability to degrade cellulose. A considerable degree of resistance to Paraquat was exhibited by Fusarium spp. (Fusarium nivale and Fusarium solni var. argillaceum) and Hormodendrum sp. (L-11), which retained their cellulolytic activity even at Paraquat rates of 6 μg/mL, whereas Hormodendrum sp. (L-10) retained its cellulolytic activity even at twofold higher rates of Paraquat (12 μg/mL).