The growth of oak seedlings was enhanced by using spore fluid from Boletus reticulatus

Growth and nutrient acclimation of evergreen oak seedlings infected with Boletus reticulatus in infertile colluvial soil in warm temperate monsoon Asia: evaluation of early growth

Masazumi Kayama (a)

(a) Department of Plant Ecology, FFPRI, Tsukuba, Ibaraki, Japan.

Forests, 11(8), 870, August 2020 DOI：10.3390/f11080870( External link )

Evergreen oaks, which are the main tree species of laurel forests, have formed a symbiotic relationship with mushroom species called ectomycorrhizal fungi. The spores of these ectomycorrhizal fungi ("seeds" in the plant world) coexist with the roots of the plants, where they help the plants to absorb water and nutrients such as phosphorus and nitrogen. Therefore, it is known that these fungi will help to promote the growth of seedlings if the seedlings are inoculated with them before planting. However, inoculation has required expensive equipment for the separation and culture of mycorrhizal fungi, so it has not been possible to perform inoculations in a simple manner.

In the present study, spores of the ectomycorrhizal fungus Boletus reticulatus, which flourishes in laurel forests, were used to develop a simple method for inoculating oak species such as Quercus acuta, Quercus glauca, and Quercus salicina, and to clarify the effects that this had on seedling growth. First, oak seeds were planted in pots filled with sterilized soil and grown into seedlings. Next, fruiting bodies of B. reticulatus (pileus parts) were cut into pieces of roughly 3cm square and wrapped in gauze and squeezed in sterilized water. The spores that were released into the water were collected to create spore fluid. This spore fluid was poured into the soil that had been filled into the pots to perform a simple inoculation. As a result, it was confirmed that after 6 months, the growth of inoculated seedlings was better than that of non-inoculated seedlings. This research will contribute to the enhancement of silvicultural techniques using ectomycorrhizal fungi.

Photo1: Fruiting bodies of Boletus reticulatus that developed in an oak forest.

Photo2: Seedlings of Quercus acuta 6 months after inoculation with Boletus reticulatus.
The two pots on the left contain colluvial soil, while the two pots on the right contain soil from a sugi cedar forest. The growth of the inoculated seedlings (the 2nd and 4th seedlings from the left) was better than that of the non-inoculated seedlings (the 1st and 3rd seedlings from the left).