Antifungal effects of 3‐(2‐pyridyl)methyl‐2‐(4‐chlorphenyl) iminothiazolidine against Sclerotinia sclerotiorum

Abstract BACKGROUND Sclerotinia stem rot (SSR) caused by Sclerotinia sclerotiorum threatens oilseed rape cultivation, and the emergence of fungicide‐resistant strains has led to control failures worldwide. Identifying novel chemical alternatives with different modes of action and high antifungal activities is thus crucial. Herein we evaluated the antifungal effects of 3‐(2‐pyridyl)methyl‐2‐(4‐chlorphenyl)imino‐ thiazolidine (PMAS) on S. sclerotiorum to determine its efficacy for SSR management. RESULTS PMAS had an inhibitory effect on mycelial growth; the EC 50 values were 17.83 and 21.15 μg mL −1 for the carbendazim‐susceptible strain Ss01 and carbendazim‐resistant strain Hm25, respectively. PMAS treatment changed the color of inhibited mycelia to green, and the hyphae were sustained in the undifferentiated stage. Cysteine supplementation made this green color disappear, whereas methionine enhanced the color. Moreover, PMAS treatment markedly inhibited oxalic acid biogenesis, increased free thiol content in mycelia, and weakened the activities of oxaloacetase and malate dehydrogenase, but had little effect on the activity of glyoxylate dehydrogenase. Cysteine could reverse the inhibitory effects of PMAS on mycelial morphogenesis and biochemical constituents, except thiol production. In the pot‐culture experiment, PMAS showed a good protective effect, with the control efficacy being >91% on SSR. CONCLUSION PMAS appears to be an effective fungicide for SSR management. © 2020 Society of Chemical Industry