Isolation, Identification and Characterization of Salt and Temperature Tolerant Pusillimonas sp.: STT-K15 with Biocontrol Potential First Time Reported from Tomato Rhizosphere Soil

The present study focused on the isolation, identification and characterization of salt and temperature-tolerant rhizobacteria isolated from the rhizosphere soil of tomato. A total of 138 isolates were obtained from the rhizosphere of tomato plants grown in the laboratory of the Department of Agricultural Microbiology, MPKV, Rahuri, Maharashtra, between 2020 and 2023, using Ashby’s Mannitol agar, King’s B and Nutrient Agar media. STT-K15 examined in Transmission Electron Microscope and found that Rod shaped, 3-3.5µm in size. Gram negative, Endospore forming, Motile in nature. Out of that STT-K15 was subjected to varying concentrations of NaCl, MgCl2, and different pH levels to evaluate their tolerance to salt and temperature stress in King’s B media. STT-K15 isolates demonstrated promising salt tolerance upto 25% NaCl concentration. Furthermore, STT-K15 showed growth at 4.0% MgCl2. Regarding to pH tolerance, STT-K15 thrived at pH 9.0. Among these, STT-K15 exhibited temperature tolerance up to 65°C. The bacterial cultures were sent to National Centre for Microbial Research Pune (India) for sequencing. Received forward and reverse sequences were merged and FASTA format sequences were further subjected to nucleotide BLAST. After identification STT-K15 was found Pusillimonas sp. Furthermore sequence was submitted to NCBI and found accession number OR432559. Pusillimonas sp. STT-K15 maximum percentage inhibition (72.5 %) against Fusarium oxysporum and 46.66% against Pestalotiopsis psidii. These findings indicate that these Pusillimonas sp. have the potential to Control Fusarium oxysporum, so it can be used as a Biocontrol agent in extreme saline and high-temperature stress condition.