Identification of bacterial isolates from rice leaves and determination of their antagonistic activity against Rhizoctonia solani Kuhn, causal organism of sheath blight of rice (Oryza sativa L.).

Date

11-2011

Degree

Bachelor of Science in Agriculture

Major Course

Major in Plant Pathology

College

College of Agriculture and Food Science (CAFS)

Adviser/Committee Chair

Ardales, Edna Y.

Abstract

A multiple cultivation assay for preliminary screening of six bacterial isolates from sheath blight-infected rice leaves was done. Only three isolates (RLB1, RLB2 and RLB6) showed inihibitory activity against Rhizoctonia solani. Dual culture assay for final screening of antagonistic activity showed that RLB6 at 0.1 OD reading (ca., 7.5x107) produced the biggest inhibition zone and growth inhibition of R. solani which possibly indicates high production of non-volatile antifungal metabolites compared with the other two isolates, RLB1 and RLB2. Microscopic examinations revealed that mycelia exposed to these three antagonists were coiled, deformed and wrinkled. Cultural, morphological, physiological and biochemical tests suggested that isolates RLB1 and RLB2 are Bacillus subtilis while RLB6 is Pseudomonas fluorescens. In the greenhouse test conducted through spraying method, Pseudomonas sp. RLB6- treated plants (ca., 3.2 x108 cfu/ml) showed the highest antagonistic activity with a relative lesion height comparable to fungicide-treated plants both in eradicative and protective applications. Generally, bacterial isolates showed more antagonistic activity when applied as protectants. In the seed bacterization experiment, induced seed germination and improved seedling height were observed suggesting the probable plant growth promoting activity of the bacterial antagonists. However, disease incidence and severity after 26 days were not assessed due to the early termination of the bacterization experiment brought about by Trichoderma sp. contamination.

Language

English

Location

UPLB Main Library Special Collections Section

Call Number

Thesis

Document Type

Thesis

This document is currently not available here.

Share

COinS