Correlations Between Indigenous Mycoparasitic and Symbiotic Beneficial Fungi at Heavy Metal Stress

Abstract

The abundance and diversity of indigenous Trichoderma fungi were tested for correlations with the natural colonization of symbiotic arbuscular mycorrhizal fungi (AMF) in Cd-, Zn- and Ni-polluted soils. Infection frequency (F%) and arbusculum richness (a%) of the mycorrhiza fungi were estimated on red clover grown in a pot experiment set up with calcareous loamy chernozem soil contaminated with Cd, Ni and Zn salts (in 0, 30, 90 and 270 mg kg -1 dry soil concentration) in the field, eight years prior to the pot experiment. Correlation analyses were used to assess the effect of different heavy metal loads on the interrelations of these two types of beneficial fungi. When the test was performed for single variables, significant correlations could be found with very close (r > 0.96 at p < 0.05) results. The rate and direction (positive or negative) of correlations, however, varied with the type of heavy metals. With the combinations of some Trichoderma and mycorrhiza parameters a significant model was obtained for the infection frequency (R² = 0.9405 at p = 0.0062) and for arbusculum richness (R² = 0.997 at p = 0.0007), which suggests a significant complex influence between the symbiotic (AMF) and the free-living ( Trichoderma ) beneficial fungi. This interaction was altered by heavy metals. In the Ni treatments, the correlation data were always negative between the two groups of beneficial fungi.