Banana Blood Disease Caused by Ralstonia syzygii subsp. celebesensis in Thailand: Pathogen Characterization and Evidence of Insect-Associated Transmission

Banana Blood Disease (BBD), a devastating bacterial wilt caused by Ralstonia syzygii subsp. celebesensis, was confirmed in Thailand in 2014 following initial detection in Yala province. Building upon recent molecular identification studies, this research provides comprehensive pathogen characterization from infected Hin banana plants displaying characteristic reddish-brown bacterial exudate. On tetrazolium chloride medium, isolates produced slow-growing, circular, red colonies with white halos typical of the pathogen. Molecular identification using 16S rDNA sequencing confirmed the isolates as R. syzygii subsp. celebesensis with 99.56% and 99.65% similarity to Blood Disease Bacterium A2-HR MARDI reference strain (GenBank Accession Nos. OR864369 and OR864371). Koch's postulates were fulfilled through successful artificial inoculation of Musa acuminata × balbisiana cv. Saba with a disease index of 76.50%. Three insect species (Tineovertex antidroma, Coryptilum klugii, and Cosmopolites sordidus) were consistently associated with infected plants. Viable R. syzygii subsp. celebesensis was successfully isolated from Tineovertex sp. and Coryptilum klugii oviposition sites on banana fruits, while C. sordidus was observed contributing to pathogen dispersal following plant death from bacterial infection. This report of BBD in Thailand represents a significant eastward expansion of the pathogen's range and documents preliminary evidence of pathogen association with insect oviposition sites, with important implications for regional banana production and quarantine strategies. These findings provide critical baseline data for developing integrated disease management strategies in Southeast Asian banana production systems.