Plant Growth Promoting and Antagonistic Potential of Endophytic Bacteria Isolated from Melon in Indonesia

Background and Objective: Bacterial endophytes, bacteria that reside within plant tissues without causing disease, can act as plant beneficial microbes. This study was carried out to determine the melon endophytic bacteria for their potential in plant growth enhancement and disease management strategies. Materials and Methods: The bacterial endophytes were explored from healthy melon plants in Yogyakarta and Central Java, Indonesia. The isolated bacteria were screened for their ability to produce extracellular enzymes (proteases and endoglucanase) and Indole-3-Acetic Acid phytohormone (IAA), to solubilize inorganic phosphate and to perform antagonistic effect against Acidovorax citrulli and Fusarium oxysporum f.sp. melonis. Bacteria that have the potential to be plant growth promoters and antagonists were molecularly identified by partial 16S rDNA sequence analysis. Results: Seven endophytic bacterial isolates were obtained, which were isolated from the roots, stems, petioles and leaves of healthy melon plant tissues. All the bacterial isolates were able to produce extracellular protease enzymes, to synthesis IAA and to inhibit the growth of F. oxysporum f.sp. melonis. Meanwhile, some of them could produce endoglucanase enzymes, solubilize inorganic phosphate and inhibit the growth of A. citrulli. Two representative isolates that showed the best results (KP B51 and Klt D01) were identified as genera Bacillus and Burkholderia, respectively. Conclusion: Molecular identification based on 16S rRNA gene sequences analysis suggested that the potential endophytic bacteria were close related to genera Bacillus and Burkholderia. The explored beneficial bacteria have possibility as alternatives for sustainable eco-friendly plant disease management in melon.