Quantification of fungal activity in arbuscular mycorrhizal symbiosis by polyacrylamide gel electrophoresis and densitometry of malate dehydrogenase

• Published in: Soil biology & biochemistry 1994, Vol.26 (11), p.1483-1489
• Main Authors: Thingstrup, Ida, Rosendahl, Søren
• Format: Article
• Language: English
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(94)90088-4

A standardized method for quantifying the malate dehydrogenase (MDH) activity of arbuscular mycorrhizal fungi in plant roots is described. The assay distinguishes the enzymatic activities of the obligately biotrophic fungi from the activity of enzymes of the host plant and is based on densitometric measurement of fungal MDH after electrophoretic separation of the host and fungal enzymes. Using this assay, the activity of the fungal enzyme was measured during the colonization of cucumber roots. When the enzyme activity was related to the amount of fungal colonization in the roots, a decrease with time was found in the enzymatic activity relative to colonization. The influence of sublethal doses of the fungicide benomyl on the MDH activity has also been investigated using the densitometric method as well as a histochemical staining for the enzyme alkaline phosphatase. Both methods showed that doses of benomyl comparable to field doses inhibited the fungal enzyme activity.