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ISOLATION AND IDENTIFICATION OF RICE PHYLLOSPHERE BACTERIAL ANTAGONISTSAGAINTS Xanthomonas oryzae pv. oryzae

CAUSES OF BACTERIAL LEAF BLIGHT IN RICE (Oryza sativa)

Hanna Karunia Agnita, Ari Susilowati, Ratna Setyaningsih

Department of Biology, Faculty of Mathematics and Natural Sciences,

Sebelas Maret University

36A Ir. Sutami Street, Kentingan, Surakarta

ABSTRACT

Bacterial leaf blight (BLB) disease caused by bacteria Xanthomonas oryzae pv. oryzae (Xoo) commonly attacks rice crops and causes agricultural product loss. Phyllosphere bacteria in healthy plant tissue can inhibit the growth of pathogenic bacteria by producing bioactive compounds. This study aimed to isolate rice phyllosphere bacteria, test its inhibition activity to Xoo pathogen, and identify antagonist isolates that can be used as prospective biological control agent of BLB disease.

Phyllosphere bacteria was isolated from rice leaves sample in healthy plants among HDB-infected plants in Sukoharjo, Boyolali, and Wonogiri. It was isolated by spread plate method in Actinomycetes agar media. Antagonist test against Xoo was done by using plug agar method. Inhibition zone formed was measured then. Cell morphology characters of antagonist phyllosphere bacteria were determined by Gram staining. Species identity was determined by 16S rRNA gene sequence analysis.

There were 42 phyllosphere bacteria isolates. Nine isolates inhibited Xoo in weak category,that wasindicated by a clear zone around the isolates colony. The greatest inhibition zone was in 7,4 mm apparent. Phyllosphere bacteria antagonist Xoo obtained based on BLASTN analysis had 96% and 95% similarity (isolate A12 and G6) indicated that these strains were new species similar to Pseudomonas sp. and Bacillusamyloliquefaciens respectively, isolate A26 and A28 were Pseudomonas sp. with 97% similarity, isolate H6 was Bacillus sp. with 99% similarity, and isolate E1, E3, H7, H9 were Microbacterium sp. with 98% and 97% similarity respectively.   

Keywords: phyllosphere bacteria, Xoo, antagonist, 16S rRNA

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