Paenibacillus polymyxa and Bacillus aryabhattai as Biocontrol Agents against Ralstonia solanacearum In Vitro and In Planta

Abstract

The present study aimed to biologically controlling the potato bacterial wilt disease which caused by Ralstonia solanacearum by antagonistic bacterial isolates which isolated from soil. Two bacterial isolates (coded, MAS400 and MAS100) obtained from soil of some field grown potato crops was tested to against Ralstonia solanacearum bacterium in vitro and in planta. The isolates showed various ability to inhibit R. solanacerum growth in vitro. The isolate MAS400 exhibited highly inhibitory activity (3.7 cm), while the isolate MAS100 showed moderate antagonistic activity (0.9 cm). Molecular identification and 16S rDNA sequencing for the antagonistic bacterial isolates showed that, the isolate MAS400 is Bacillusaryabhattai withpercent identity 80.56% and the isolate MAS100 is Paenibacillus polymyxa withpercent identity 97.63% compared to known bacterial sequences in the NCBI (National Center for Biotechnology Information) databases. The isolate MAS100 was deposited in Genebank NCBI with accession number MN971671. Assessment of antagonistic bacteria as biocontrol agents for suppressionpotato bacterial wilt disease showed that, symptoms were less severe and the appearance of wilt symptom on infected plants was delayed compared to the control. Trials with Paenibacillus polymyxa isolate on potato plants had a lower disease incidence (20 %) with maximum disease reduction (80 %), whereas Bacillusaryabhattai isolate had a higher disease incidence on potato plants (60 %), with lower disease reduction (40 %). Isolates Paenibacillus polymyxa showed the highest suppression on potato plants.