American chestnut was eliminated as a canopy tree from the Appalachian region of North America with the introduction of chestnut blight in the early 1900s. Breeding programs initiated in the 1980s have produced seedling lines that display the pure American morphology with potential resistance to chestnut blight. More work is required to assess their field performance in field sites representative of their native range. This study used American (Castanea dentata) and backcrossed hybrid chestnuts (C. dentata × C. mollissima) on an abandoned coal mine in southeastern Ohio. Half of the seeds were planted with ectomycorrhizal fungus (ECM) Pisolithus tinctorius (Pt) as a granular inoculum. Germination, survival, percent ECM colonization, and ECM community were assessed. In addition, soil data such as pH, cation exchange capacity, nutrients, texture, temperature, moisture, and organic matter were evaluated to determine their influence on ECM. After the first and second growing season, germination and survival were not influenced by the Pt inoculum or chestnut genotypes. In addition, ECM root colonization, fungal community composition, and host response were similar between seedling types, regardless of the inoculum added. This indicated: 1) backcrossed breeding produces seedlings similar to pure American chestnuts with regard to growth, establishment, and fungal symbionts, and 2) the granular inoculum had no influence on ECM colonization in this field site. Introducing spore inoculum to a field site greatly deficient in nutrients and organic matter is not an efficient method to ensure ECM symbiosis. However, natural colonization by native ECM fungi, though limited, did result in larger chestnut seedlings. Cation exchange capacity significantly contributed to the percent of root colonization of ECM fungi on chestnut. Determination of planting protocols and factors that influence ECM root colonization will be useful for in future mine restoration projects using backcrossed American chestnut as a restoration tree
