The effect of fungicides on vesicular‐arbuscular mycorrhizal symbiosis

Abstract

SUMMARYTwo experiments were conducted under controlled environmenta] conditions to determine the effects of the three fungicides, Benlate'^, Aiiette" and Ridomil", on efficiency of P uptake from the soiJ and transfer across the living plant-fungal interface of onion plants iAllium lepa L.) associated with Glomus sp. "City Beach' (WUM 16). P applied to the soil did not apparently increase the rate of transfer (flux) of P to the plant via the futigal partner of the mycorrhiza.Benlate reduced P inflow and transfer across the interface in one of the experiments. The rate of P uptake per m living external hyphae was not affected but, as de\elopment of li\'ing external hyphae in the soil was reduced. the contribution of the fungus to P uptake was small. Aliette reduced growth of both sboots and roots, but apparently increased the accumulation of P in the tissues compared with controls. Ridomil reduced P inflow per m of root and P uptake per m living external hyphae, but had no effect on the rate of P transfer across the interface. This led to a reduction in the overall contribution of the fungus to P nutrition.

Field evidence for the carbon cost of citrus mycorrhizas

“…There are several possible reasons to explain why trees did develop P deficiency : (1) trees were planted from the commercial nursery with stored P ( 0n20 % leaf P) that was re-allocated for growth ; (2) root systems had pre-established mycorrhizal colonization when transplanted, and even though further development and activity was inhibited by benomyl, some mycorrhizal-mediated uptake of P occurred even at low P supply ; (3) slow-growing perennial Citrus on the four rootstocks had a relatively low P demand compared with supply of P that the expanding root system and mycorrhiza hyphal network had access to from the soil volume ; (4) trees were sufficient in nutrient content and otherwise well-watered and fertilized with other macronutrients and micronutrients ; or (5) soil-water status and nutrient availability in the low P-fixing Candler fine sand was not as restrictive to diffusion and mass flow of P as might be expected in finer textured soils of higher buffering capacity. The second possibility is supported by studies that indicate benomyl inhibited P uptake, transport and possibly transfer through the plantmycorrhizal fungus interface (Sukarno et al, 1993(Sukarno et al, , 1996, but benomyl did not reduce fungal alkaline phosphatase activity of G. caledonium colonizing cucumber (Larsen et al, 1996). This raises the possibility that different mycorrhizal species in the soil population vary in their sensitivity to benomyl.…”

Impact of Biocontrol Pseudomonas fluorescens CHA0 and a Genetically Modified Derivative on the Diversity of Culturable Fungi in the Cucumber Rhizosphere

“…Peronosporales were not found in this work, but metalaxyl may display a wider specificity towards fungi considering that it inhibits rRNA synthesis. Indeed, there is evidence that arbuscular mycorrhizal fungi are sensitive to metalaxyl (58). Interestingly, treatment effects were greater in the fifth cycle than in the first cycle for the CHA0-Rif(pME3424) treatment (Fig.…”

Influence of adverse soil conditions on the formation and function of Arbuscular mycorrhizas

“…Interaction of multiple fungicides on the function of mycorrhizas is important in the context of minimizing effects of plant pathogens while maximizing beneficial effects of mycorrhizas to plant nutrition (Abd-Alla et al, 2000;Sukarno et al, 1996). Several studies have found that benomyl inhibits arbuscular mycorrhizal infection and P uptake in crop plants.…”