Growth stimulatory substances and the axnic culture of vesicular-arbuscular mycorrhizal fungi

通过使用巴伊亚草根25%的MeOH洗脱液，我们首次成功地培养了一种泡状丛枝菌根（VAM）真菌，Gigaspora ramisporophora （Ishii et al., 1995）。此次成功培养不仅为扩大VAM真菌工农业利用的可能性，而且为开展真菌生理生态特性的研究做出了重要贡献。在本研究中，我们对巴伊亚州草根中VAM刺激物质的分离和鉴定进行了研究，并对VAM真菌的培养方法进行了改进。此外，我们还调查了巴伊亚州基层VAM感染率的季节变化。结果表明：1)从巴伊亚根25% MeOH洗脱液中分离出3种VAM真菌生长刺激物质。其中一种鉴定为eupalitin（3.5-二羟基-6,7-二甲氧基-4′-羟基黄酮）。在10 ppm时，该化合物显著促进了g.s ramisporophora的体外菌丝生长。其他的在这项研究中没有被确定。2)开发了一种高效的VAM真菌培养培养基。在该培养基中检测了几种化学物质对VAM真菌菌丝生长的影响，海藻酸寡糖、多胺、异戊二醇和未发表物质均能促进菌丝生长。特别是，未发表的物质对VAM孢子的萌发非常有效。3) 6月中旬至9月上旬，巴伊亚州基层VAM感染率在50%以上。特别是，在8月初和中旬观察到的百分比最高。

By using the 25% MeOH eluates of Bahia grass roots, we first succeeded in the axnic culture of a vesicular-arbuscular mycorrhizal (VAM) fungus, Gigaspora ramisporophora (Ishii et al., 1995). This success of the culture will make a great contribution to not only extending the possibility of agricultural and industrial utilization of VAM fungi, but also developing the studies about the physiological and ecological properties of the fungi. In this study, we examined the isolation and identification of VAM-stimulatory substances from Bahia grass roots and the improvement of our axnic culture methods of VAM fungi. In addition, we investigated seasonal changes in VAM infection rate of Bahia grass roots. The results obtained are shown as follows :1) Three kinds of the growth stimulatory substances for VAM fungi were isolated from the 25% MeOH eluates of Bahia grass roots. One of them was identified as eupalitin (3.5-dihydroxy-6,7-dimethoxy-4'-hydroxy flavone). At 10 ppm, this compound significantly stimulated the in vitro hyphal growth of G.ramisporophora. The others were not indentified in this study.2) We developed an efficient medium for the culture of VAM fungi. When effects of some chemicals on hyphal growth of VAM fungi were examined in this medium, the growth was stimulated by alginate oligosaccharides, polyamines, eupalitin, and unpublished substances. In particular, the unpublished substances were quite effective on the germination of VAM spores.3) The percentage of VAM infection in Bahia grass roots was 50 and above for the period from mid june to early September. Particularly, the highest percentage was observed in early and mid August.