Biocontrol Efficacy of Siderophore Producing Indigenous Pseudomonas Strains Against Fusarium Wilt in Tomato

Two bacterial strains were screened for in vitro antagonism against tomato wilt pathogen Fusarium oxysporum f.sp. lycopersici. They were assessed for siderophore production qualitatively and quantitatively. Strains SPs9 and SPs20 produced 59.30 and 52.74 µg ml−1 siderophore and exhibited 3.4 and 3.8 cm fungal inhibition zone respectively in deferrated SSM. Zone size decreased as iron in SSM increased. Fungal inhibition zone for SPs9 in SSM without and with 2.5, 5, 7.5 and 10 µM iron was 3.4, 2.1, 1.5, 0.9 and 0.6 cm whereas for SPs20, 3.8, 2.2, 1.7, 1.0 and 0.7 cm. The biocontrol potential of strains was evaluated through greenhouse assay. Inoculation of tomato seedlings with SPs9 caused 100% and SPs20, 75% disease control and increased fresh and dry weight of plants. Both strains were genetically identified as P. fluorescens.