Diversity of Endophytic Bacteria and their Potential as Biological Agents Against Rigidoporus microporus Causes White Root Disease in Hevea brasiliensis

Abstract

The big problems of rubber (Hevea brasiliensis) horticulture are the present of pathogenic fungus, Rigidoporus microporus, which causes white root disease. Endophytic bacteria have potential to inhibit the pathogenic fungus. This study aims to isolate, identify and evaluate the diversity of endophytic bacteria that can suppress the growth of R. microporus on rubber. Identification of endophytic bacteria based on morphology characters and molecular marker using 16S rRNA primer. In vitro assessments of biological agents were carried out using fermentation medium. In vivo tests were carried out in the nursery using rubber. The isolation results obtained 55 isolates of endophytic bacteria. Isolate B49 from bark showed the highest percentage of inhibition against the growth of R. microporus (82.47%), then followed by isolates D8 (81.44%) and D20 (72.16%) from leaves, and A27 (61.86%) from roots. The 16S rRNA gene sequence of the D8 isolate exhibited 98% similarity to Bacillus paramycoides, D20 isolate was shown 95% similarity to Acinetobacter nosocomialis, A27 isolates identified as Enterobacter cloacae (99%), and B49 identified as Bacillus cereus (99%). In addition to inhibiting the growth of R. microporus, several endophytic bacterial isolates used in this study were shown to be able to solubilize phosphate thus suppress white root disease. Bacillus D8, Acinetobacter D20, and Bacillus B49 can be used to control white root disease in rubber plantations. Selected bacteria isolated from rubber have the potential to be used as a biocontrol and as a biofungicide against white root disease caused by R. microporus. HIGHLIGHTS• Endophytic bacteria have potential to suppress Rigidoporus microporus causes white root disease.• Endophytic bacteria can solubilize phosphate, which plays a role in reducing the disease index.• Endophytic bacteria have potential as biocontrol and biofungicide against white root disease.