Triadimefon: Mode of action in plants and fungi

Triadimefon retarded the elongation of the upper internodes of shoots of tomato and cotton plants. The growth retardation was completely reversed by exogenously applied gibberellic acid (GA3). Growth of coleoptiles, primary leaves and roots of wheat and barley seedlings was reduced after seed treatment with triadimefon; application of GA3 did not completely counteract this growth retardation. Leaves of triadimefon-treated plants showed a darker green colour; leaves became lighter again when the growth retardation was reversed by GA3 application. When detached leaf sections were floated in triadimefon solutions or suspensions in the dark, senescence was delayed. The compound showed only a weak antagonistic effect on GA3-induced α-amylase synthesis in barley endosperm. Triadimefon strongly reduced the synthesis of gibberellin-like substances in Fusarium moniliforme. It inhibited the development of haustoria of Erysiphe graminis f. sp. hordei. Studies on its mode of action revealed that triadimefon blocked ergosterol biosynthesis in Ustilago avenae.