Effect of Arbuscular Mycorrhizal Fungi with Their Helper Microorganisms on Root Colonization and Growth of Trifoliate Orange Seedlings

摘要

Several kinds of helper microorganisms isolated from spore surfaces of Gigaspora margarita, an arbuscular mycorrhizal fungus (AMF) , have been reported to promote the growth of Gi. margarita by producing gaseous compounds including ethylene or non-gaseous compounds (Horii and Ishii, 2006). In this study, we investigated the effect of AMF with their helper microorganisms on AMF root colonization and growth of trifoliate orange seedlings. Ten days after the inoculation of Gi. margarita into one-yearold trifoliate orange seedlings, 4 kinds of helper microorganisms, Woollsia root associated fungus XV (Accession Number #AY230785) KHIMF1, Cladosporium cladosporioides KHIMF3, Bacillus asahii KHIMB1 and Methylobacterium sp. KHIMB2 were individually applied to the rhizospheres of the seedlings. Three months after the application, the seedlings were harvested. All of the helper microorganisms used increased the percentage of root colonization and total fresh weight of the seedlings. In particular, the inoculation of 3. 2×108 cells of B. asahii induced a remarkable stimulation on root colonization and tree growth compared with the control (Gi. margarita only). Our results show that the inoculation of AMF with their helper microorganisms is very useful to promote plant growth stimulation.