ABSTRACT

A total of 11 isolates were isolated from the soil samples, among which 5 isolates were screened from tomato rhizosphere soil sample and 6 isolates from paddy rhizosphere soil sample. Eleven isolates were tested for the production of siderophore using blue agar medium. Out of the 11 isolated cultures, 4 cultures namely C2, C3, C8, C11 were found to produce siderophore. Based on morphology, cultural characteristics and biochemical tests the siderophore producing isolates were identified.  Based upon the results C2 was identified as Non-fluorescent Pseudomonas sps, C3 as Bacillus sps, C8 as Fluorescent Pseudomonas sps and C11 as Azotobacter sps. The eight fungal isolates were isolated from Sabaroud’s chloramphenicol agar. The isolates were named as F1, F2, F3, F4, F5, F6, F7, and F8. The bacterial cultures namely C2, C3, C8, C11 were tested for their antifungal activity against the fungal isolates F3, F4, F7, F9.  Non fluorescent Pseudomonas showed 83.5% activity against Fusarium sps. Bacillus sps exhibited 85.8% inhibition against Sclerotium sps, 90.5% inhibition against Fusarium sps, 41.8% inhibition for Alternaria sps. Fluorescent Pseudomonas showed 92.9% activity against Sclerotium sps, 83.5% inhibition for Fusarium sps, 38.1% inhibition against Alternaria sps. Azotobacter sps had antagonistic activity of 92.9% against Sclerotium sps, 45.4% antagonism for Alternaria sps. Maximum activity was observed for Alternaria sps by Bacillus sps (C3)32±0.5mm, Fluorescent Pseudomonas sps (C8) 34±0.1mm and Azotobacter sps (C11) 30±0.4mm.

Keywords : Siderophore; Pseudomonas sps; Bacillus sps; Azotobacter sps,; Fusarium; Alternaria