Abstract
Tomato bacterial wilt caused by Ralstonia solanacearum is one of the most destructive soil-borne diseases. Many strategies have been taken to improve soil suppressiveness against this destructive disease, but limited success has been achieved. In this study, a novel bioorganic fertilizer revealed a higher suppressive ability against bacterial wilt compared with several soil management methods in the field over four growing seasons from March 2011 to July 2013. The application of the bioorganic fertilizer significantly (P<0.05) reduced disease incidence of tomato and increased fruit yields in four independent trials. The association among the level of disease incidence, soil physicochemical and biological properties was investigated. The soil treated with the bioorganic fertilizer increased soil pH value, electric conductivity, organic carbon, NH4 +-N, NO3 --N and available K content, microbial activities and microbial biomass carbon content, which were positively related with soil suppressiveness. Bacterial and actinomycete populations assessed using classical plate counts were highest, whereas R. solanacearum and fungal populations were lowest in soil applied with the bioorganic fertilizer. Microbial community diversity and richness were assessed using denaturing gel gradient electrophoresis profile analysis. The soil treated with the bioorganic fertilizer exhibited higher bacterial community diversity but lower fungal community diversity. Redundancy analysis showed that bacterial community diversity and richness negatively related with bacterial wilt suppressiveness, while fungal community richness positively correlated with R. solanacearum population. We concluded that the alteration of soil physicochemical and biological properties in soil treated with the bioorganic fertilizer induced the soil suppressiveness against tomato bacterial wilt.
Highlights
Bacterial wilt caused by the vascular pathogen, Ralstonia solanacearum has resulted in serious damage in agricultural crop production [1]
Our results demonstrated that 1) the application of bioorganic fertilizer more efficiently controlled bacterial wilt than other soil amendment methods, 2) the application of bioorganic fertilizer significantly improved soil physicochemical and biological properties, 3) the alteration in soil physicochemical and biological properties after the application of bioorganic fertilizer induced the suppressive capacity towards bacterial wilt
R. solanacearum population in the B treatment was decreased by 23–24% in Trial 1 and by 8–36% in Trial 2 during the entire experiment period compared with the control (Fig 1A), while no difference was observed between the O and control treatments in both trial periods
Summary
Bacterial wilt caused by the vascular pathogen, Ralstonia solanacearum has resulted in serious damage in agricultural crop production [1]. Biocontrol and use of organic amendments such as compost, manure and plant residues emerge as environmentally friendly strategies and popular methods to suppress soil-borne disease. The use of organic amendments as a promising alternative to suppress the soil-borne disease less depends on chemicals. Organic fertilizers can supply adequate energy and nutrients for antagonists to improve the suppressive capacity towards pathogens [13]. The combination of organic fertilizers and antagonists (termed bioorganic fertilizer in our study), as a novel strategy to control bacterial wilt, showed best results in tobacco [10] and potato [15], and decreased bacterial disease incidences successfully. Few studies focus on the suppressive capacity of soil treated with bioorganic fertilizers towards tomato bacterial wilt in the field
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