Estimation of mycorrhizal colonization of the roots of oak seedlings inoculated with an ectomycorrhizal fungus, Laccaria amethystea

Six-month-old seedlings of Quercus serrata and Quercus glauca in a nursery were inoculated with the ectomycorrhizal fungus Laccaria amethystea encapsulated in alginate gel and grown in the nursery. The seedlings were collected at 1, 3, and 5 months after the inoculation and examined for colonization of the root system with ectomycorrhizal fungi. The roots within 5 months after the inoculation showed rudimentary ectomycorrhizal colonization. The level of colonization of the root system was estimated based on the intensity of hyphal covering on the root tips by staining with a fluorescent dye and expressed as an index of mycorrhizal colonization (IMC). IMC increased with the time after inoculation and reached values of 4 and 12% in Q. serrata and Q. glauca, respectively at 5 months after the inoculation. The determination of IMC may enable to assess the development of mycorrhizal colonization of the root system that shows rudimentary ectomycorrhizas after the inoculation.