Screening of Endophytic Bacteria as Biocontrol Agents Against Bacteria Leaf Blight (Xanthomonas oryzae)

Rashidah Abd Halim,Kogeethavani Ramachandran,Nor'Aishah Hasan

doi:10.4308/hjb.27.3.215

Abstract

Bacterial leaf blight (BLB) is one of major threats in rice production as it can cause 100% yield loss. Concern on the environment and human health has led an attempt to replace existing methods of chemical control and avoid extensive use of bactericides by using endophytic bacteria. The present study was conducted to screen and characterize bacteria isolated from different sources that has potential as antagonistic bacteria against Xanthomonas oryzaepv. oryzae (Xoo), the causal agent of bacterial leaf blight of paddy. Two hundred and thirty-three endophytic bacteria were successfully isolated from roots and leaves from paddy field. Only 17 endophytic bacterial isolates showed positive antagonistic activity indicated by inhibition zone around bacterial colony against Xoo on nutrient agar plate with 2 endophytic isolates (BCA 3 and BCA 12) showed highest inhibitory effect with 35±0.00 mm in diameter. Molecular identification by 16S rRNA amplification successfully identified the antagonistic endophytic bacteria as Pseudomonas fluorescensand Geobacillus thermoparaffinivorans. Findings in this study revealed the biocontrol abilities of isolated endophytes as an excellent option to be used by agriculture sectors to have sustainable environment.

Highlights

Rice is the most important food crop of the developing world and the staple food of more than half of the world’s population
The present study was conducted to screen and characterize bacteria isolated from different sources that has potential as antagonistic bacteria against Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial leaf blight of paddy
Pulau Pinang were selected in this study to evaluate the potential of isolated bacteria endophytes as biocontrol agents against Xoo

Summary

Introduction

Rice is the most important food crop of the developing world and the staple food of more than half of the world’s population. In Malaysia, rice is cultivated on 8 major granary area with average rice consumption by Malaysian citizen is about 82.3 kilograms per year (Raweekul and Wuttitummaporn 2016). The average growth rate of rice yield in Malaysia was decreased due to the infection of rice plant from the microbial disease’s incidence. Bacteria leaf blight (BLB) caused by Xanthomonas oryzae has recently become a common disease among rice crop in Malaysia. Moist conditions at the beginning of the season is the major factor enable the bacteria to grow from infected stubble to an adjacent seedling (Hogg et al 2010). Farmers often heavily rely on using chemical bactericides to control these plant diseases as well as enhance

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