Abstract
The objective of this study was to investigate the in vitro influence of glyphosate (Roundup®) on growth and sporulation of Pyrenophora teres and Rhynchosporium secalis in agar petri plate cultures. Agar media amended with glyphosate concentrations of 0, 0.025, 0.050, 0.075, 0.100, 0.125, 0.250, and 0.500 µL/mL were inoculated with a spore suspension of R. secalis or a mycelial plug of P. teres. Colony diameter for P. teres was monitored at 2, 4, and 7 days after inoculation. Sporulation was assessed after 7 days for P. teres and 14 days for R. secalis. The lowest concentration of glyphosate reduced in vitro sporulation of R. secalis by 60% compared with the untreated check. In contrast, glyphosate led to an increase in sporulation of P. teres at concentrations of 0.05–0.250 µL/mL with sporulation decreasing slightly when the concentration reached 0.500 µL/mL. There was a small reduction in P. teres colony growth at the higher concentrations of glyphosate.