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

通过使用巴伊亚草根的25%MeOH洗脱液，我们首次成功地进行了泡囊-丛枝菌根（VAM）真菌Gigasporramisporophora（石井等人，1995年）。这一培养的成功，不仅为扩大VAM真菌在农业和工业上的应用提供了可能，而且也为进一步开展VAM真菌的生理生态学研究做出了贡献。本研究从巴伊亚植物根中分离鉴定了VAM刺激物质，并对VAM真菌的培养方法进行了改进。此外，我们调查了巴伊亚基层VAM感染率的季节变化。1）从巴伊亚草根的25%MeOH洗脱液中分离到3种对VA菌根真菌有生长刺激作用的物质。其中一个化合物经鉴定为泽兰素（eupalitin，3.5-dihydroxy-6，7-dimethoxy-4 '-hydroxy flavone）。在10 ppm，该化合物显着刺激在体外菌丝生长的G. ramisporophora。2）研制了一种适合VAM真菌培养的高效培养基。当一些化学物质对VAM真菌菌丝生长的影响进行了研究，在这种培养基中，生长刺激藻酸盐寡糖，多胺，泽兰素，和未发表的物质。3）6月中旬至9月上旬，巴伊亚地区VAM侵染率在50%以上。特别是，在8月上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fungi were examined in this medium, the growth was stimulated by alginate oligosaccharides, polyamines, eupalitin, and unpublished substances. In particular, the unpublished substances were quite effective on the germination of VAM spores.3) The percentage of VAM infection in Bahia grass roots was 50 and above for the period from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.