Endophytic bacterial consortium originated from forestry plant roots and their nematicidal activity against meloidogyne incognita infestation in greenhouse

Abstract

Yield loss due to root-knot nematode Meloidogyne incognita infection is reported to reach 35%, depends on factors contributing to infection. Application of several endophytic bacterial isolates (bacterial consortium) to control pathogenic infection is reported to be more effective compared to the application of single bacterial isolate. This study was aimed to obtain endophytic bacterial consortium originated from forestry plant that is effective to control root-knot nematode. The study was conducted through bacterial isolation followed by biosafety test. Bacterial isolates that were found to be safe for plants and mammals and compatible with each other were further grouped as the endophytic bacterial consortium. Phenotypic characterization and physiological characteristics including Gram type, ability to produce protease, chitinase, and lipase enzymes as well as HCN volatile compound were also tested. Moreover, the ability to fix nitrogen and dissolve phosphate were also examined. The endophytic bacterial consortium consisted of several bacterial isolates was further tested for its ability to inhibit M. incognita egg hatching and increase J2 of M. incognita mortality in vitro. Furthermore, test on tomato plants infested with 500 J2 of M. incognita was also performed in the greenhouse. Test results showed that 70 bacterial isolates were successfully isolated from Shorea sp., Swietenia sp., Albizia falcataria, Anthocephalus cadamba, and Juglans nigra. However, 34 bacterial isolates were observed to be safe (did not cause hypersensitivity reaction and did not produce hemolytic toxin). According to physiological characteristics, it was found that 25 isolates were able to produce protease enzyme, 26 isolates were able to produce chitinase enzyme, and 14 isolates were able to produce lipase enzyme. Moreover, it was also detected that 11 isolates were able to produce HCN volatile compound, 23 isolates were able to fix nitrogen (N), and 24 isolates were able to dissolve phosphate (P). Endophytic bacterial consortium obtained in this study was also observed to be able to inhibit M. incognita egg hatching up to 81.33% and increase J2 of M. incognita mortality up to 85% compared to control. In addition, the application of endophytic bacterial consortium was also able to increase the growth of tomato plant infected with M. incognita, and suppress the severity of the root-knot disease. This study provided information that endophytic bacterial consortium originated from forestry plants has the potential as a biocontrol agent of M. incognita.