Saito Katsuharu, Suyama Yoshihisa, Sato Shusuke, Sugawara Kazuo
Graduate School of Agricultural Science, Tohoku University, Kawatabi, Narugo, 989-6711 Miyagi , Japan.
Mycorrhiza. 2004 Dec;14(6):363-73. doi: 10.1007/s00572-003-0286-x. Epub 2004 Jan 15.
The effects of defoliation on arbuscular mycorrhizal (AM) associations in the field were investigated in terms of the community structure of AM fungi colonizing roots of grassland plants; the carbohydrate balance of the host plants was also determined. We focused on two plant species dominating Japanese native grasslands: the grazing-intolerant species Miscanthus sinensis and the grazing-tolerant species Zoysia japonica. Community structures of AM fungi were determined from 18S rRNA gene sequences. The dominant fungal group in both plant species was the Glomus clade, which was classified into several phylogenetic groups based on genetic distances and topology. In Miscanthus roots, the Glomus-Ab, Glomus-Ac, and Glomus-Ad groups were detected almost equally. In Zoysia roots, the Glomus-Ab group was dominant. Defoliation effects on the community structure of AM fungi differed between the plant species. In Miscanthus roots, the percentage of root length colonized (%RLC) by the Glomus-Ac and Glomus-Ad groups was significantly reduced by defoliation treatment. On the other hand, AM fungal group composition in Zoysia roots was unaffected by defoliation except on the last sampling date. Decreased %RLC by Glomus-Ac and Glomus-Ad coincided with decreased non-structural carbohydrate (NSC) levels in host plants; also, significant positive correlations were found between the %RLC and some NSC levels. On the other hand, the %RLC by Glomus-Ab in both plant species was unaffected by the NSC level. These results suggest that AM fungal groups have different carbohydrate requirements from host plants.
从定殖于草原植物根系的丛枝菌根（AM）真菌的群落结构方面，研究了田间去叶处理对AM共生关系的影响；同时还测定了寄主植物的碳水化合物平衡。我们重点关注了两种在日本原生草原占主导地位的植物物种：不耐放牧的芒草和耐放牧的结缕草。通过18S rRNA基因序列确定AM真菌的群落结构。两种植物物种中的优势真菌类群均为球囊霉属分支，根据遗传距离和拓扑结构将其分为几个系统发育组。在芒草根系中，几乎等量地检测到了球囊霉-Ab组、球囊霉-Ac组和球囊霉-Ad组。在结缕草根系中，球囊霉-Ab组占主导地位。去叶处理对AM真菌群落结构的影响在不同植物物种间存在差异。在芒草根系中，去叶处理显著降低了球囊霉-Ac组和球囊霉-Ad组的根长定殖率（%RLC）。另一方面，除了最后一个采样日期外，结缕草根系中的AM真菌类群组成不受去叶处理的影响。球囊霉-Ac组和球囊霉-Ad组的%RLC下降与寄主植物中非结构性碳水化合物（NSC）水平的降低相一致；此外，还发现%RLC与某些NSC水平之间存在显著的正相关关系。另一方面，两种植物物种中球囊霉-Ab组的%RLC不受NSC水平的影响。这些结果表明，AM真菌类群对寄主植物的碳水化合物需求不同。
