Relationship of soil properties and soil amendments to response of Glomus intraradices and soybeans

Knowledge of the role of soil properties on mycorrhizal relationships with host plants may contribute to the ecological understanding of the fungus and its effectiveness in indigenous or introduced soil conditions. This study examined the response of Glomus intraradices, an arbuscular mycorrhizal (AM) fungus, and soybean host in five benchmark soils. Glomus intraradices increased, with a few exceptions, shoot dry weight, root length, shoot phosphorus, and shoot zinc in all soils. Soil amendments (nitrogen, phosphorus, and pH adjustments) affected mycorrhizal hyphal length per plant and hyphal to root length ratio, as well as shoot Zn. Interactions among soil properties, soybean plant, and this mycorrhizal isolate suggested that soil properties, such as pH, pore diameter, and silt and organic matter, may have difficulties predicting arbuscular mycorrhizal fungal response. However, before soil amendment, regression models were accurate in predicting shoot dry weight, mycorrhizal colonization, and hyphal development of this mycorrhizal isolate on plants. When soil amendments were added to the soil property regression model, the predictive ability of the model was greatly reduced or nonexistent. The observations in this study indicate the effects of soil properties on root colonization and external hyphal production are important in examining AM fungal - plant interaction. An understanding of soil properties will be essential to understand mycorrhizal fungal ecology and to effectively use mycorrhiza in biological systems.