BACTERIAL wilt disease caused by Ralstonia solanacearum is a
serious threat for agricultural production of tomato. In this study,
80 endophytic bacterial isolates were isolated from healthy tomato
plants in R. solanacearum-infested fields. Two endophytic antagonists
designated HRA32 and HRA69 showing the highest antagonistic
activity via in vitro screening were identified as Pseudomonas
fluorescens and Bacillus subtilis using 16S rRNA analysis. The
selected isolates were evaluated in vitro for their activities related to
plant nutrition and plant growth regulation. Both of the assessed
endophytes were found to exhibit capabilities in ammonia, indole
acetic acid (IAA) and siderophore production as well as phosphate
solubilization. Pot experiments were adopted to test the control
efficiency against tomato bacterial wilt. Results revealed that HRA32
and HRA69 significantly reduced disease incidence when applied as
separate treatments. The clear synergetic effect was observed in
tomato plants treated with a mixture of the two antagonists reducing
disease incidence significantly from 87.22% in the control to 16.66%
with biological control efficacy of 80.23%. It is concluded that
application of P. fluorescens HRA32 and B. subtilis HRA69 may be a
promising approach for biological control of the tomato bacterial wilt
and may play an important role in sustainable agriculture.