Castanea sativa Mill. seedlings were inoculated with mycelial cultures of Amanita caesarea (Scop.: Fr.) Pers. and Boletus edulis Bull.: Fr.
Mycorrhizal synthesis was confirmed in the laboratory for 40 plants of each type.
The mycorrhizal seedlings were planted in April 1992 in an open field, previously used as a permanent pasture, near Cuneo, Italy.
The number and distribution of mycorrhizae per plant were recorded for each plant on the planting date.
All of the trees were subsequently grafted on to commercial cultivars of chestnut.
The orchard has been intensively managed, according to standard commercial chestnut growing techniques.
The evolution of the mycorrhizae has been studied by periodic sampling of root tips.
The first sampling, in 1996, indicated that despite the sporadic presence of Scleroderma areolatum Ehrenb. and Tomentella sp. mycorrhizae, about 80% of the trees still presented abundant A. caesarea and B. edulis mycorrhizae.
The second examination of the root systems, in July 1998, confirmed the persistence of A. caesarea mycorrhizae on 88% of the Amanita-inoculated plants, and B. edulis mycorrhizae on 82% of the Boletus-inoculated plants.
Eighty-five percent of the trees also had S. areolatum mycorrhizae; a notable increase over the first sampling date.
The occurrence of Tomentella sp. was unchanged.
Three plants had two unidentified basidiomycetes mycorrhizae.
Fruitbodies of A. caesarea and B. edulis. have not been observed, although there have been abundant fructifications of Scleroderma areolatum.
These preliminary results show that "weed" species such as Scleroderma areolatum can quickly colonize the roots of young host plants, entering into competition with the valuable "cultivated" species.
Finding ectomycorrhizal species not present at the moment of planting hints at the delicate symbiotic equilibrium evolving in relation to the ecology of the soil and the age of the plant.