Isolation of siderophore- producing strains of rhizobacterial fluorescent pseudomonads and their biocontrol against rice fungal pathogens.

Rice blast caused by Magnaporthe grisea and sheath blight caused by Rhizoctonia solani are the major diseases affecting the rice production. Application of beneficial bacteria as seed or seedling root dip to protect these diseases may be an alternative strategies to chemical control. In this study, fluorescent Pseudomonads isolated from rice seedlings were used to screen for their antagonistic ability and siderophore mediated antibiosis under in-vitro conditions against these pathogens. Among 10 isolates, strain P.f 003 gave significantly higher inhibition of mycelial growth of M. grisea and R. solani. Strains of P.f 001, P.f 003, P.f 005 and P.f 007 produced siderophores when grown on Fe deficient and Fe fortified King’s B medium. These strains again tested for their in-vitro antagonistic activity against M. grisea and R. solani on King’s B media with or without FeCl3. Our results showed that all these strains significantly reduced the growth of M. grisea and R. solani with FeCl3 in the media compared to without FeCl3. Strain P.f 003 activity was superior compared to other strains evaluated.