DisplayTitle

Ultrastructural Alterations in Fusarium sambucinum and Heterobasidion annosum Treated with Aluminum Chloride and Sodium Metabisulfite

First author: Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa (On), Canada, K1S 5B6; second and third authors: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 10380, Québec (Qc), Canada, G1V 4C7; and first, fourth, and fifth authors: Centre de recherche en horticulture, Université Laval, Québec (Qc), Canada, G1V 0A6.

Aluminum chloride (AlCl₃) and sodium metabisulfite (Na₂S₂O₅) have received increasing attention as antifungal agents for the control of plant diseases. In an effort to understand their toxic action on fungi, ultrastructural changes and membrane damage in Fusarium sambucinum (Ascomycota) and Heterobasidion annosum (Basidiomycota) in response to salt exposure was investigated using transmission electron microscopy. Conidial membrane damage was quantified using SYTOX Green stain, which only enters altered membranes. The results showed that mortality of the conidia was generally closely associated with SYTOX stain absorption in F. sambucinum treated with Na₂S₂O₅ and in H. annosum treated with AlCl₃ or Na₂S₂O₅, suggesting that these salts cause membrane alterations. For both fungi, ultrastructural alterations in conidia treated with AlCl₃ and Na₂S₂O₅ included membrane retraction, undulation, and invagination. At higher concentrations or exposure periods to the salts, loss of membrane integrity, cytoplasmic leakage, and cell rupture were observed. Ultrastructural alterations and increased SYTOX stain absorption in salt-treated conidia appear consistent with a mode of action where AlCl₃ and Na₂S₂O₅ alter membrane integrity and permeability.

Additional keywords:conidial mortality.