Root Colonization by Ericoid Mycorrhizae and Dark Septate Endophytes in Organic and Conventional Blueberry Fields in Michigan

Ericoid mycorrhizae are interfaces for nutrient exchange between specialized fungi and roots of blueberries and other ericaceous plants. Dark septate endophytes also associate with roots of the Ericaceae and many other plant families, but the nature of the interaction is not well understood. We measured ericoid mycorrhizae and dark septate endophyte colonization in organic and conventional blueberry fields matched by soil series and, if possible, cultivar and field age. The percentage of hair root cells with ericoid mycorrhizae was generally higher in organic than conventional fields, while dark septate endophyte colonization was higher in sand than muck soils. Across both muck and sandy soil types, ericoid mycorrhizal colonization was negatively correlated with field age, and dark septate endophyte colonization was negatively correlated with soil carbon, total soil nitrogen, and soil ammonium levels. When only sandy soils were included in the analysis, ericoid mycorrhizal colonization was positively correlated with soil pH and hair-root diameter, and negatively correlated with field age, soil ammonium levels, and total soil nitrogen. On sandy soils, dark septate endophyte colonization was not correlated with any measured variable. The functions of ericoid mycorrhizae and dark septate endophytes in commercial blueberry fields require further investigation.