Testing a biocontrol agent consortium for suppression of tomato bacterial wilt through rhizosphere microecological regulation

Abstract

Tomato bacterial wilt (TBW) caused by Ralstonia solanacearum leads to severe crop losses. The aim of the present study was to construct a biocontrol agent consortium (BAC) and evaluate its efficiency against TBW. Bacillus tequilensis FJAT-51047 and Streptomyces fradiae FJAT-31535 were isolated from healthy tomato rhizosphere soils and had intense antagonistic ability against R. solanacearum and high control efficiency against TBW. The mixture of fermentation broths of FJAT-1458 (an avirulent strain of R. solanacearum), FJAT-51047 and FJAT-31535 with a ratio (v:v:v) of 1:1:1 had the highest control efficiency of 100 % in a pot experiment and was used as the BAC. When it was applied in a 6-year continuous cropping field, the BAC could (1) enhance soil organic carbon, total nitrogen and phosphorus, and total potassium contents by 34.18, 38.46, 115.44, and 17.41 %, respectively, at the reproductive stage; (2) increase soil urease activity by 36.54 and 9.63 % at the vegetative and reproductive stages, respectively; (3) increase tomato yield by 113.46 %; and (4) reach a control efficiency of 84.10 %. The BAC significantly enriched rhizosphere soil with the beneficial bacteria Bauldia, Altererythrobacter, Pseudolabrys, Ferruginibacter and Rhodoplanes, and inhibited the pathogen-related bacteria Ralstonia and Aquicella. Redundancy analysis revealed a negative relationship between rhizosphere soil physicochemical parameters (pH, SOC, TN, TP and TK) and TBW disease incidence (DI) or the R. solanacearum population. Overall, BAC could be used for microecological regulation of the tomato rhizosphere to control TBW.