Susceptibility of the common root rot causal agent of cereals Bipolaris sorokiniana to fungicides of different chemical composition

The aim of research is to study the susceptibility of Bipolaris sorokiniana, isolated in the Sukhobuzimsky District of the Krasnoyarsk Region, to fungicides of different chemical compositions. The following fungicides were tested: Vitaros (carboxin 198 g/l + tyram 198 g/l), Lamador (prothioconazole 250 g/l + tebuconazole 150 g/l), Oplot (difenoconazole 90 g/l + tebuconazole 45 g/l), Maxim (fludioxonil 25 g/l) and Vial TrasT (tebuconazole 60 g/l + thiabendazole 80 g/l). A decrease in the germination of B. sorokiniana conidia in the presence of various concentrations of fungicides was used as an indicator of antifungal activity. It was found that the drug Vitaros exhibits the maximum fungicidal activity against B. sorokiniana, which provides 100 % suppression of conidia germination even when the working solution is diluted 16 times. In second place in terms of efficiency is Lamador, for which a 100 % inhibitory effect on the germination of conidia is retained when the working solution is diluted by 2 times. Fungicide Maxim provided 100 % suppression of the germination of conidia in the working solution, however, it lost efficiency when the working solution was diluted 2 times. The fungicides Oplot and Vial TrasT were ineffective against B. sorokiniana. Germination of conidia in the working solution was 64 and 95 % of the control, respectively. Curves "dose-effect" for Vitaros and Lamador drugs are adequately described by the Michaelis-Menten equation (coefficients of determination, respectively, 0.992, 0.999 and more than 0.999). The dose-effect curve for Maxim is adequately described by a linear equation (coefficient of determination 0.982). The results of the study show that the regional population of B. sorokiniana is resistant to difenoconazole, tebuconazole, and thiabendazole, but is sensitive to carboxin, thiram, and prothioconazole.