Radiolabelling and Tracer Analysis of Endophytic Bacteria in Noni and Its Antagonistic Activity Against Root-Knot Nematode, Meloidogyne incognita

Endophytes are symbiotic microorganisms that colonize the interior of plants, and support the plant growth and are involved in natural plant protection against pathogenic organisms. Noni, Morinda citrifolia is considered as a miracle plant with more than 150 nutraceuticals, that help the human body in various ways. The root knot nematode, Meloidogyne incognita is a serious pest of noni. Endophytic strains of Bacillus subtilis were isolated from noni plants and their antagonistic effect against root knot nematode was studied. In vitro evaluation of six Bacillus strains revealed that the crude antibiotic of the strain Bs 5 hindered egg hatching and increased juvenile mortality after 72 h of exposure. Radiolabelling and tracer analysis was done to study the translocation and colonization potential of Bs 5 in noni by tagging it with radioisotope ³²P. In vivo distribution of the bacteria traced using autoradiography revealed that the bacteria effectively colonized the actively growing young leaves, stem and mid ribs.