Abstract
Rhizosphere bacteria have the ability to protect the host plants from the infection of pathogenic microorganisms. This study aimed to identify rhizosphere bacteria that were capable of inhibiting the growth of bacterial isolates that cause tuber rot of Amorphophallus muelleri . Rhizosphere bacteria were isolated using Nutrient Agar medium by pour plate method. Isolates were subjected to antagonistic assay against several bacterial isolates from the rotten tuber of A. muelleri using dual culture method. The potential isolate was identified based on 16S rDNA sequence. Isolate R7 showed the strongest inhibition to the growth of bacterial isolates from rotten tuber with an inhibition zone diameter of 19.66 mm. The 16S rDNA sequence of isolate R7 R7 was 99.7% similar to Delftia tsuruhatensis PCL1755. The isolate was potential to be developed as phytopathogen control agent. Keywords: Amorphophallus , antagonistic bacteria, rhizosphere bacteria, rotten tuber, 16S rDNA .
Highlights
The common pathogenic microorganisms that attack the tubers are Erwinia caratovora and Pectobacterium caratovora on Amorphophallus konjac tuber [2,3] and Dickeya dadantii on Amorphophallus rivieri [4,5]
This research aims to analyze the potency of isolated rhizosphere bacteria to inhibit A. muelleri tuber rot bacteria and to identify the potential rhizosphere bacteria based on 16S rDNA sequence
Antagonistic Potency of Rhizosphere bacteria Rhizosphere bacteria consisting of nine isolates with a density of 107 CFU.mL-1 were tested for their inhibition against three tuber rot bacteria of A. muelleri (PT4, PL9, and PR11)
Summary
Soil samples were obtained from the rhizosphere of A. muelleri from Rejosari Village, Bantur City, East Java Province, Indonesia. Each suspension of 0.1 mL was transferred into Nutrient Agar (NA) medium in the Petri dishes according to pour plate method and incubated at room temperature for 72 hours. Each bacterial colony was enumerated and purified according to the spread plate method. Sample suspension of 0.1 mL was inoculated into NA medium according to pour plate method and incubated at room temperature for 48 hours. The bacterial colony was purified according to the spread plate method and pure cultures were stored at 4°C. The 100 μL suspension of isolated tuber rot bacterium with 106 cells.mL-1 density was spread on NA medium and directly incubated at 4°C for 4 hours. The bacteria isolate was identified based on 16S rDNA sequence similarity. The phylogenetic tree was constructed based on Neighbor-Joining with bootstrap 1000 using the MEGA 6.00 program [31,32,30]
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