DIRECT APPLICATION OF CARBENDAZIM AND PROPICONAZOLE AT FIELD RATES TOTHE EXTERNAL MYCELIUM OF 3 ARBUSCULAR MYCORRHIZAL FUNGI SPECIES - EFFECT ON P-32 TRANSPORT AND SUCCINATE-DEHYDROGENASE ACTIVITY

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 P -32 transport and succinate dehydrogenase (SDH) activity in external h yphae 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 in to two root-free hyphal compartments (HCs). The fungicides were applie d to each HC 24 days after sowing and P-32 was added to one HC of each pot. Four days later, the fungicide effect on fungal P transport was measured as the difference in P-32 content of treated and untreated pl ants. SDH activity in fungal hyphae was determined in the HCs given no P-32. Carbendazim severely inhibited P-32 transport and SDH activity in external hyphae at an application rate of 0.5 mu g g(-1) soil. The ergosterol inhibitor propiconazole affected none of these parameters. The fungicides had similar effects on all three fungal species, althou gh P transport efficiency and SDH activity differed markedly between t he fungi.