Sensitivity of eight fungi in rice paddy soil to four fungicides

Based on sequence of the internal transcribed spacer (ITS)-5.8s rDNA region, eight dominant fungal strains were isolated and preliminarily identified. The growth rate method was used to measure the inhibition activity of four representative fungicides including prochloraz, carbendazim, triadimefon and jingangmycin to the eight fungi, and the joint action of carbendazim and prochloraz on Puccinia gramiris, Aspergillus niger and Trichoderma longibrachitum. The results showed that prochloraz strongly inhibited the mycelial growth of eight species of fungi with the EC50 values ranged from 0.091 to 3.1 mg/L, while the EC50 values of carbendazim and triadimefon ranged from 0.15 to 1.8 mg/L and from 0.57 to 8.5 mg/L, respectively. However, the fungi showed low sensitivity to jingangmycin, with EC50 values ranged from 12 to 94 mg/L. SSDs curve-based analysis of the fungicide indicated that there were significant differences between the sensitivity of different fungi to fungicides. When the mixed ratios of carbendazim and prochloraz were 3:2, 1:1 and 7:3(V/V), the synergistic coefficient were 1.615, 1.039 and 1.042, respectively, suggesting carbendazim and prochloraz have synergistic or additive effect on the fungi to some extent. The results of present study primarily provides basis for further elucidation of ecological influence of fungicide in situ and rational use of fungicide in rice paddy eco-system.