The In Vitro and In Planta Interspecies Interactions Among Rice-Pathogenic Burkholderia Species

Burkholderia glumae, B. plantarii, and B. gladioli are responsible for serious diseases in rice crops and co-occurrence among them has been reported. In this study, in vitro assays revealed antagonistic activity among these organisms, with B. gladioli demonstrating strong inhibition of B. glumae and B. plantarii. Strains of B. glumae and B. plantarii that express green fluorescent protein were constructed and used for cocultivation assays with B. gladioli, which confirmed the strong inhibitory activity of B. gladioli. Cell-free supernatants from each species were tested against cultures of counterpart species to evaluate the potential to inhibit bacterial growth. To investigate the inhibitory activity of B. gladioli on B. glumae and B. plantarii in rice, rice plant assays were performed and quantitative PCR (qPCR) assays were developed for in planta bacterial quantification. The results indicated that coinoculation with B. gladioli leads to significantly reduced disease severity and colonization of rice tissues compared with single inoculation with B. glumae or B. plantarii. This study demonstrates the interactions among three rice-pathogenic Burkholderia species and strong antagonistic activity of B. gladioli in vitro and in planta. The qPCR assays developed here could be applied for accurate quantification of these organisms from in planta samples in future studies.