Sugar beet seed-associated bacteria: their identification and effects on seed germination

Sugar beet seed plays an important role in the transmission of beneficial or detrimental bacteria. To identify and evaluate the effects of sugar beet seed-associated bacteria on seed germination, cleaned but not disinfected seeds were provided from Sugar Beet Research Department at Hamadan Agricultural Research Center. A total of 80 endophyte and epiphyte bacterial strains were isolated from the seeds. Based on the protein pattern and according to Laemmli method, three representative electrotypes were selected and their biochemical and molecular characteristics were evaluated. Based on the biochemical test results and sequencing of the 16S rRNA gene of the representative strains Stenotrophomonas rhizophila and Pseudomonas geniculata were identifiedas epiphytic and Stenotrophomonas maltophilia as endophytic species, respectively. To perform seed germination test, three different groups were generated based on the strain effect on seed germination. Seed germination test was conducted based on the inoculation of five representative strains from each group in completely randomized design with four replications. Each replication included a Petri dish containing 10 seeds. Results showed that seeds inoculated by S. maltophilia strain had the highest germination percentage (90), germination rate (0.0174 per hour), shoot fresh weight (100 mg), radicle fresh weight (126.2 mg), shoot dry weight (50 mg), radicle dry weight (43.7 mg), shoot length (6.5 cm), radicle length (8 cm), and the lowest seed uniformity compared with control. In order to improve germination indices and seedling growth, it is recommended to inoculate sugar beet seed with S. maltophilia bacterium.