Isolation and Characterisation of Rhizosphere Soil Bacteria and the Inhibition Effect on White Rot Fungus Isolated From Oil Palm (Elaies Guineensis)

Ganoderma sp. causes basal stem rot (BSR) in oil palm (Elaeis guineensis). This disease could destroy the palm tree and spread easily in plantation. There is still no effective way to prevent or treat this disease. Paenibacillus sp. is a potential biocontrol agent since it has inhibitory effect on many types of bacteria and fungus. The objective of this project is to isolate the bacteria from rhizosphere soil to study its effectiveness to suppress the growth of white rot fungus isolated from oil palm plantation. The fruiting bodies were collected from the affected oil palm in Muar, Johor. The identity of the fungus was confirmed by sub-culturing onto GSM (Ganoderma selective medium), DNA extraction, PCR using universal primers ITS1 and ITS4 and DNA sequencing. The culture on PDA and GSM showed the formation of brown rings, which indicated high chance of the present of Ganoderma sp. The bacteria isolated were screened through the biochemical tests such as starch hydrolysis test and peroxidase test. All 3 strains selected (R1, R2 and R3) were Gram-positive, rod-shape, starch hydrolysis positive, 2 strains were catalase positive and only 1 strain showed the formation of capsule. The 16srRNA gene was amplified using primers PAEN515F and 1484R, then subjected to sequencing for identification of the bacteria. The Ganoderma sp. and different strains of isolated bacteria were used for dual culture test. Data were collected after 3, 5, 7 and 10 days. Out of 4 bacterial isolates, R1 is the solely effective biocontrol agent for the fungus isolated. The highest percentage of inhibition of radial growth (PIRG) was 50% on Day 3, which is significantly higher (P<0.05) as compared to other bacteria isolates. The optimal time for the dual culture was 7 days, since most of the bacteria isolates have highest PIRG on day 7. In conclusion, bacterial isolate R1, identified as Bacillus sp. showed the capacity to inhibit white rot fungal isolate, identified as Inonotus sp.