Rhizosphere Community Analysis of Tomato Plants and Characterization of Plant Growth Promoting Flavobacterium Strains
1*Dong-A Univ, Busan 604-714, Republic of Korea*
Plants have a close interaction with rhizosphere microbes that influence various plant functions such as plant growth promotion (PGP) and stress tolerance. Microbial community analysis of tomato plant rhizosphere revealed that the phylum Bacteroidetes significantly increased in rhizosphere of tomato plants than bulk soil. Especially, members in the family Flavobacteriaceae were dramatically increased. A pair of specific primer targeting those bacteria in family Flavobacteriaceae was designed and used to select bacterial isolates in a member of the family Flavobacteriaceae by colony PCR of bacterial colonies derived from tomato plant rhizosphere. A number of bacteria were isolated and examined for phenotypes relevant to plant-beneficial interaction, such as biofilm formation, seedling growth promotion, and antimicrobial activities. On the basis of PGP activities, five strains of Flavobacterium were selected. When germinated seeds treated with Flavobacterium were transferred to sterilized farm soil in greenhouse, PGP effect was apparent four weeks after transplanting. An isolate Flavobacterium TCH3-2 is likely a novel species that showed significant growth promotion of tomato than other species. Genomes were analyzed for all five strains in Flavobacterium and revealed that they harbor genes for plant growth promotion, such as auxin biosynthesis and ethylene removal, and for secondary metabolites which may be involved in beneficial effect to plants. However, a novel species Flavobacterium TCH3-2 did not contain any known genes for beneficial interaction with plant, while plant growth promotion effect and the capability of biofilm formation were remarkable. We are under investigation of bacterial gene expression in planta for these Flavobacterium strains.
keywords:Flaovbacterium,Rhizosphere community,Plant growth promotion,Tomato