Morphological and molecular characterization of Burkholderia glumae causing panicle blight of paddy

Abstract

Bacterial panicle blight (BPB) is one of the emerging diseases of paddy in the Tarai region of Uttarakhand. The present investigation was conducted to isolate and identify the cause of BPB, to detect the pathogen longevity in in-vitro stored paddy seeds and glass house conditions and to identify the most susceptible stage for pathogen infection. 42 rice panicle samples from different paddy growing regions of the Tarai areas were analyzed, and the bacterium was isolated from different parts of paddy seeds. The isolated bacterial strains were characterized culturally in semi-selective media (S-PG), morphologically (SEM) and molecularly (16S rRNA). A total of 16 samples produced yellow colored colonies on King's B medium and 9 samples produced brisk yellow colored colonies on the S-PG agar suggesting them to be of B. glumae. However with PCR reactions we found that 2 strains out of 9 were of B. glumae and the causal agent for the other sample remains unknown. Recovery of bacterium from infected stored seeds was also studied at monthly intervals from harvest to next growing season and maximum recovery was observed from the seeds just after harvest (91%) which although decreased with the storage period but the bacterium did not get completely eliminated during the course of storage. On exploring the different growth stages for most susceptible stage of infection, boot leaf and panicle initiation stages were found to be equally susceptible with 93.33% disease incidence. These findings suggest that B. glumae is distributed generally in the paddy seed and can also survive in it for a longer duration thereby acting as a source of inoculums for the next cropping season. These findings will help to understand the mode of survival of bacteria in plants and its longevity in seeds.