Mycorrhizal development in a chestnut orchard introduced by a sod culture system with Vulpia myuros L. C. C. Gmel.

摘要

When mycorrhiza development in a chestnut orchard introduced by a sod culture system with Vulpia myuros was investigated, we found arbuscular mycorrhizal (AM) fungal root colonization in the spring before ectomycorrhizas became dominant. AM fungal root colonization rates of chestnut using V. myuros, however, were higher than those in the control (a bare orchard with herbicides). Although no ectomycorrhizal (ECM) fungal root colonization was observed before chestnut flower abscission, the rate of ECM fungal root colonization remarkably increased during the flower abscission from early June to late June, and its rate of increase remained high until late September when it began to gradually decrease. The tendency of ECM development in chestnut roots using V. myuros was much the same as that in the control roots, but the development in June was stimulated by use of V. myuros. Spermidine, an AM fungal growth stimulant, was detected as a major polyamine in chestnut flowers, and its concentration was 10.9 mg/g fresh weight (FW) of the flowers. In an experiment in vitro, 0.5 and 5 mM spermidine stimulated mycelial growth of a chestnut ECM fungus. These results suggest that the introduction of a sod culture system using V. myuros into chestnut orchards can contribute to the enhancement of ECM fungal activities as well as AM activities, and that spermidine in chestnut flowers may affect mycorrhizal development of chestnut trees.