การคัดเลือกแบคทีเรียปฏิปักษ์จากบริเวณรอบรากข้าวที่มีประสิทธิภาพในการควบคุมเชื้อแบคทีเรียสาเหตุโรคของข้าวก่ำ

Abstract

The bacterial disease symptoms of purple rice were observed at the Mae Hia Agricultural Research, Demonstration and Training Center, Chiang Mai, Thailand. Twenty-five isolates were obtained from bacterial leaf blight symptoms. Pathogenicity assays were performed on two growth stages (seedling and tillering stages) of the purple rice variety Kum Chao CMU 107. The results showed that three isolates, including UN13, UN32, and KDK6, infected rice leaves and caused bacterial leaf blight symptoms. At seedling stage, the bacteria UN13 was the most severe pathogen. The UN13 caused leaf blight and Kresek symptoms. Whereas UN32 and KDK6 were not pathogenic at the seedling stage. However, after 21 DPI at the tillering stage, the three isolates caused bacterial leaf blight symptoms. The bacteria UN13 were the most severe pathogen at the tillering stage while, UN32 and KDK6 were minor. Based on 16S rRNA sequencing, the pathogens were identified as Pantoea ananatis UN13, Luteibacter yeojuensis UN32 and Sphingomonas sp. KDK6. These were related to morphological and biochemical characteristics. Forty-eight isolates of antagonistic bacteria were isolated from the rhizosphere soil of rice. The high efficacy of antagonistic bacteria was selected by using the dual culture method. The results showed the bacteria KY16 and KY17 were the most efficient antagonists that inhibited three isolates of the bacterial leaf blight pathogen and had the same level of control over each pathogen. Based on 16S rRNA, gyrA and rpoB gene sequences, the antagonists KY16 and KY17 were identified as Bacillus siamensis. Antimicrobial biosynthesis genes were also investigated for the antagonistic bacteria. The results revealed that iturin A and surfactin biosynthesis genes were detectable. Moreover, KY16 and KY17 performed as a plant growth promoting rhizobacteria (PGPR) by producing siderophores and solubilizing inorganic phosphate.