Direct application of carbendazim and propiconazole at field rates to the external mycelium of three arbuscular mycorrhizal fungi species: effect on 32P transport and succinate dehydrogenase activity

TLDR: The systemic fungicides propiconazole and carbendazim had similar effects on all three fungal species, although P transport efficiency and SDH activity differed markedly between the fungi.

Abstract: The influence of the systemic fungicides propiconazole (Tilt 250E) and carbendazim (Bavistin) at field application rates on the functioning of three arbuscular mycorrhizal fungi was studied. Short-term fungal 32P transport and succinate dehydrogenase (SDH) activity in external hyphae of Glomus intraradices Schenck and Smith, G. claroideum Schenck and Smith and G. invermaium Hall in symbiosis with pea (Pisum sativum L.) were measured. In the experimental system used, the hyphae grew into two root-free hyphal compartments (HCs). The fungicides were applied to each HC 24 days after sowing and 32P was added to one HC of each pot. Four days later, the fungicide effect on fungal P transport was measured as the difference in 32P content of treated and untreated plants. SDH activity in fungal hyphae was determined in the HCs given no 32P. Carbendazim severely inhibited 32P transport and SDH activity in external hyphae at an application rate of 0.5 μg g–1 soil. The ergosterol inhibitor propiconazole affected none of these parameters. The fungicides had similar effects on all three fungal species, although P transport efficiency and SDH activity differed markedly between the fungi.