Effect of Soybean Selective Herbicides on Mycelium Growth Rate of Macrophomina phaseolina (Tassi) Goid, Soybean Charcoal Rot in Vitro

Herbicides are widely used in various fields, but the mechanism of all possible interactions between herbicides and plant have hot been well understood yet. Charcoal rot, caused by Macrophomina phaseolina, is one of the most important diseases of soybean. Imazethapyr, trifluralin and metribuzin herbicides are used as soil -applied herbicides in soybean. Experiment arranged as factorial in Completely Randomised Design (CRD) with 6 replications in a laboratory condition in order to study of zero to 7000 mg.l-1 concentrations of imazethapyr, trifluralin and metribuzin herbicides in Potato Dextrose Agar on medium culture phaseolina mycelium growth rate. Fungus disc was placed on the center of 9 cm petri dishes and mycelium growth was measured daily. Growth rate of mycelium was fitted using four parameters logistics dose - response equation. Results showed that different doses of herbicides have significant effect on fungal growth rate. Trifluralin at 4320 and 5760 ppm, imazethapyr at 2300 and 7000 ppm and metribuzin at 5000 and 7000 ppm concentrations completely ceased the growth of fungus. Imazethapyr showed the most inhibitory effects on M. phaseolina isolates in the PDA medium culture followed by metribuzin and trifluralin.