Isolation and potential of Ochrobactrum sp. NW-3 to increase the growth of cucumber.

*Corresponding Author E-mail: huang_zy@tib.cas.cn Tel.: +86-022-84861931 Fax: +86-022-84861931 ‘Biofertilizers’ have been defined as alternative substances, to chemical fertilizers, which can stimulate plant growth and increase yield. Plant growth promoting bacteria (PGPB) represent the main component of biofertilizers. We chose seven bacteria with higher nitrogenase activity, from twenty-nine nitrogen fixing bacteria isolated from different natural environments, to evaluate the effects of bacteria inoculation on cucumber under controlled (pot) conditions. Furthermore, growth promoting characteristics (indole-3acetic acid (IAA), ACC-deaminase activity, siderophores production, phosphorus solubilization and potassium solubilization ability) were evaluated for seven strains and identification of strains was carried out by amplification, sequencing and comparison in GenBank database for 16S rDNA genes. Ochrobactrum sp. NW-3 had a high ability to increase the growth of cucumber in pot experiments and this strain showed the five factors evaluated to stimulate the plant growth. For this reason, Ochrobactrum sp. NW-3 was used to perform a field experiment in Anshan, Liaoning Province, the main local economic for cucumber production. Cucumber yield and quality increased significantly after three months of field experiment, suggesting that Ochrobactrum sp. NW-3 can exert promoting growth effect under the complex field environment. It is the first report on the use of Ochrobactrum sp. for stimulating cucumber growth and yields successfully in field experiments.