Biocontrol of tomato wilt by plant growth-promoting rhizobacteria

In greenhouse experiments, three strains of plant growth-promoting rhizobacteria (PGPR), Serratia sp. J2, fluorescent pseudomonad J3, and Bacillus sp. BB11, were evaluated for biological control of bacterial wilt of tomato caused by Ralstonia solanacearum. A total of four field trials were conducted, each in a different location in Jiangsu and the Hebei provinces. Strains J2, J3, and BB11 provided disease control and increased yield. In trial one in Qixia (1999), disease was reduced 66.1, 73.6, and 68.4% by J2, J3, and BB11, respectively, compared to the control. Yield increases with bacteria in this trial ranged from 49.5 to 70.8%. In trial two in Huaian (2000), disease was reduced 78.1, 94.1, and 86.9% by J2, J3, and BB11, respectively. Yield increases ranged from 180 to 237%. In trial three in Handan (1999), biocontrol efficiencies of 71.3, 63.6, and 78.2% were achieved by J2, J3, and BB11, respectively. Yield increases ranged from 53.5 to 76.2%. In trial 4 in Handan (2000), disease was reduced 74.4, 75.1, and 81.9% by J2, J3, and BB11, respectively, compared to the control. Yield increases with these bacteria ranged from 46.3 to 78.5%. Additional tests were conducted with 1-year-old and 2-year-old formulations of each PGPR strain. Populations of PGPR in the 1-year-old formulations were nearly identical to freshly prepared PGPR formulations. Biological control efficacy was retained by the stored formulations of all three PGPR strains, with 1-year-old formulations providing 68.4-99.5% control and 2-year-old formulations providing 63.4-78.5% control. Yield increases with stored formulations ranged from 35.4 to 67.0%. We conclude that our method of formulating PGPR products provides stable formulations that retain biological control and plant growth-promoting activities. (C) 2003 Elsevier Science (USA). All rights reserved.