Vol. 12, Issue 9 (2023)

Author(s):
Satyam, AM Navale, SV Kolase, TK Narute, AA Kale, AV Chandanshive, AG Durgude and MS Barge

Abstract:
This research investigates the biocontrol potential of salt and temperature-tolerant plant growth-promoting rhizobacteria isolated from the rhizosphere soil of tomato plants, aiming to combat various plant pathogens and enhance crop resilience against diseases like vascular wilt, crown gall, root rot, leaf wilt, and curling disease. Among 138 soil samples, 12 isolates were selected for comprehensive assessment through biochemical tests and biocontrol activity evaluations. Standard methods were employed to analyse indole production, urease activity, oxidase activity, starch hydrolysis, gelatin liquefaction, methyl red test, Voges-Proskauer test, H₂S production, and citrate utilization. Biocontrol activity was determined using a dual-culture plate method, wherein actively growing phytopathogenic fungi of 5 mm diameter was placed at the center of Petri plates and Bacterial isolates were streaked approximately 2.2 cm away from the phytopathogen in a circular manner, while control plates lacked bacterial streaks. Incubation was performed at 30 °C in a BOD incubator. After 4 days, the percentage of mycelial growth inhibition was calculated. Key findings revealed that: Pseudomonas furukawaii STT-A8 exhibited positive results for the oxidase test, gelatin liquefaction and citrate utilization. Achromobacter sp. STT-A12 displayed positive results for the oxidase test and citrate utilization. Agrobacterium pusense STT-A24 and STT-A39 showed positive results for indole production, urease activity, starch hydrolysis, methyl red test, and citrate utilization. Brevibacterium epidermidis STT-K2 and STT-N28 tested positive for gelatin liquefaction and citrate utilization. Priestia flexa STT-K13 and Bacillus sp. STT-K24 exhibited positive results for urease activity, oxidase activity, starch hydrolysis, gelatin liquefaction, and citrate utilization. Pusillimonas sp. STT-K15 demonstrated positive oxidase activity. Among the 12 extremely salt and temperature-tolerant rhizobacteria isolates, the highest inhibitory effects against Fusarium oxysporum were observed in Pseudomonas furukawaii STT-A8 (87.6%), Agrobacterium pusense STT-A39 (78.75%), Achromobacter sp. STT-A12 (77.5%), Pusillimonas sp. STT-K15 (72.5%), Agrobacterium pusense STT-A24 (71.25%), Priestia flexa STT-K13 (71.25%), Bacillus badius STT-N22 (70%), Bacillus badius STT-N33 (68.75%), and Bacillus badius STT-N26 (68.42%). Brevibacterium epidermidis STT-K2 (55%), Brevibacterium epidermidis STT-N28 (50%), and Bacillus sp. STT-K24 (50%) also exhibited significant inhibition against Fusarium oxysporum. This research offers valuable insights into the biocontrol capabilities of salt and temperature-tolerant rhizobacteria, positioning them as essential inoculants for disease management and the promotion of tomato plant growth in saline environments.