SDCA Journal of Biological Research

Abstract

Plant growth-promoting rhizobacteria (PGPR) are highly diverse group of soil bacteria that influence the growth of plants through different mechanisms and serves as biocontrol agent for several plant pathogens such as X. oryzae, X. campestris, and X. cassavae that causes Bacterial Leaf Blight (BLB) and Bacterial sheath rot. A total of eighteen (18) isolates were collected from six (6) rhizospheric soil samples of Oryza sativa (Rice) in two areas of Barangay Toclong, Kawit, Cavite with an interval of 10 meters to each other. After subjecting all isolates in gram staining, colonial morphology, and biochemical tests, nine (9) (50%) were found to be Pseudomonas sp. All isolates were then tested as antibacterial agent against Xanthomonas oryzae (Xoo). On the other hand, the pathogenic bacteria, Xoo, were also isolated from diseased plant samples retrieved from University of the Philippines-Los Baños which undergone gram staining, colony morphology, and biochemical tests which identified three (3) (100%) isolates and only one (1) Xoo sp. were used for the assay among six (6) bacterial isolates. Two test organisms were then subjected by using spot inhibition assay. Among nine (9) isolates, none of them can inhibit the Xanthomonas oryzae pv. Oryzae. Thus, this study demonstrated that the Pseudomonas sp. Isolated from rhizospheric soil of rice do not possess antibacterial property that can inhibit the growth of Xoo.

Keywords: Pseudomonas sp., Xanthomonas sp., inhibition spot assay, rhizospheric soil, bacterial leaf blight.