Effects of bio-organic fertilizer plus soil amendment on the control of tobacco bacterial wilt and composition of soil bacterial communities

Tobacco bacterial wilt (TBW) is caused by Ralstonia solanacearum (R. solanacearum), a severe pathogenic agent with a wide host range. In this study, lime + ammonium bicarbonate (L + AB), organic fertilizer (OF), bio-organic fertilizer (BOF), and integrated treatment (L + AB + BOF) were assessed for the ability to control TBW and to influence the composition of native soil bacterial communities. The results showed that disease incidence of L + AB + BOF for two growth seasons in pot experiment was the lowest, with only 15.56 and 11.11 % at seasons 1 and 2, respectively. The integrated treatment could also significantly suppress TBW in the field, with a disease incidence of only 14.27 % compared with 35.41, 50.03, and 31.32 % in L + AB, OF, and BOF treatments, respectively. With application of the integrated treatment in pot and field experiments, the abundances of R. solanacearum were both significantly lower than those with other treatments. Denaturing gradient gel electrophoresis (DGGE) patterns showed that application of BOF significantly affected composition of bacterial communities of rhizosphere. The analysis of 454 sequencing data showed that application of integrated treatment recruited more beneficial bacteria than other treatments, such as Bacillus, Paenibacillus, Arthrobacter, and Streptomyces, while the abundance of Ralstonia with the integrated treatment was decreased. Overall, these results suggested that application of integrated agricultural management could effectively suppress bacterial wilt by affecting the composition of bacterial community and reducing the population of R. solanacearum.