Response of an endomycorrhizal fungus in Allium porrum L. To different concentrations of the systemic fungicides, metalaxyl (Ridomil®) and fosetyl-al (Aliette®)

Abstract

Two systemic, anti-oomycete fungicides were tested for their effects on colonization of leek roots by Glomus intraradices Schenck and Smith, a vesicular-arbuscular mycorrhizal (VAM) fungus. Foliar application of the symplastic fungicide fosetyl-Al (Aliette®), at concentrations of 0.3, 1.0 or 3.0 mga.i. ml −1, to VAM Allium porrum L. (leek) plants, significantly increased colonization by Glomus intraradices, the number of intramatrical vesicles, and plant growth compared to inoculated but untreated plants. These effects did not diminish with time. In a second study, mycorrhizal infection and growth of inoculated leek seedlings were significantly reduced by soil drenches of the systemic fungicide metalaxyl (Ridomil®), at concentrations of 0.5. 1.0 or 2.0 mga.i. per plant. Inoculated but untreated plants had extensive mycorrhiza. We suggest that the probable adverse effects of metalaxyl on Glomus intraradices should be taken into consideration when its use is being considered.