Comparison of microbial community structure between soils suppressive and conducive to Fusarium-wilt of radish

抄録

Physicochemical and microbial properties of five volcanic ash soils in Fukushima Pref., Japan, suppressive and conducive to Fusarium-wilt of radish, were investigated. Suppressive soils (S-soils) showed higher total C, total N, and nitrate contents, a higher cation exchange capacity (CEC), and a lower pH than conducive soils (C-soils). Germi-nation of microconidia of the pathogen was more suppressed in the S-soils than in the C-soils, suggesting that the S-soils displayed a higher fungistatic capacity. The numbers of total bacteria, culturable bacteria, total fungal propagules and indigenous Fusarium spp., were not clearly related to the disease incidence in the soils, whereas the ratio of actinomycetes to total culturable bacteria was higher in the S-soils than in the C-soils. The microbial community structure of the soils was examined based on the %G+C profiles of soil community DNA, phospholipid fatty acid analysis (PLFA), and community-level physiological profile (CLPP) using Biolog GN plates. There was no remarkable difference in the %G+C profiles between the C-soils and S-soils. PLFA and CLPP enabled to differentiate the community structure among the soils and suggested that the substrate utilization ability, estimated from the number of substrates utilized, and the ratio of Gram-positive bacteria, estimated from the proportion of branched fatty acids, were likely to be higher in the S-soils than in the C-soils. Microbial community structure specific to the soils suppressive to Fusarium-wilt of radish was analyzed by combining the results obtained by the different methods.