Ectomycorrhizae are common features of many forest trees and particularly pines do not grow normally without forming mycorrhizae in natural habitats. Recent advancement in mycorrhizal research suggests that plant growth can be stimulated by careful selection of fungal species and artificial inoculation of plants with the selected fungi.
Two ectomycorrhizal fungi, Pisolithus tinctorius and Thelephora terrestris, were introduced from U.S.A. and inoculated to five pine species in Korea to evaluate the reported growth stimulation of host plants after inoculation. These fungi were grown as mycelial inoculum in large quantity and inoculated to the fumigated nursery soil just before seed sowing. At the end of the first growing season, Pisolithus stimulated the height growth of Pinus densiflora, P. thunbergii. P. rigida, and P. rigida × taeda by 55, 36, 69, and 37% respectively, compared with control seedlings (with no fumigation and no inoculation). When the growth stimulation was expressed with dry weight, Pisolithus increased dry weight of P. deasiflora and P. rigida × taeda by 143% and 128%, respectively, over control seedlings. Thelephora failed to stimulate growth of inoculated plants. Pinus koraiensis did not respond to the inoculation during the first growing season.
Artificial inoculation also significantly stimulated phosphorus and nitrogen uptake of host plants. Inoculated plants contained 3.35㎎ P and 29.0㎎ N per plant top, while control plants (mycorrhizae formed by natural population of fungi) had 1.68㎎ P and 13.8㎎ N per plant top. However, there was no difference among treatments in concentration of P and N in the shoots.
In the previous experiment mentioned above, the effect of Pisolithus tinctorius was not well shown in heavy soil. Therefore, subsequent experiment was conducted in the greenhouse using potted Pinus rigida × taeda to test the effectiveness of this fungus at different soil texture and soil fertility. The results of the experiment indicated that this fungus compared with naturally occurring fungi stimulated dry weight increase (at least two times) of the host giants regardless of soil texture and soil fertility. The Pisoliihus was effective in stimulation of both height growth and dry weight increase when host plants was grown in sandy soil, sandy loam, and loam with or without organic amendment. Stimulatory effect of the fungus was more prominently shown in sandy loam and loam which were not amended with organic, indicating that high fertility through organic amendment reduced the benefit of this. fungus in sandy loam and loam. However. organic amendment in sandy soil having low fertility increased dry weight of inoculated seedlings.
After the successful use of introduced two super strains of mycorrhizal fungi, we are now testing effectiveness of Korea-native fungus of Pisolithus tinctorius. Basidiospores of U.S. and Korean Pisolithus were used as inocula in this. experiment. Preliminary that the super strain introduced from U.S.A. stimulated height growth of Pinus rigida × taeda more than Korean strain collected near Suweon. However it may be possible in the future to select better strains. of this fungus from natural populations of wide distribution in Korea to maximize the benefit of the symbiosis between the fungus and host plants.
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