Abstract:

Isolation and identification of functional endophytic bacterial strains from tomato seeds to establish a foundation for developing high-efficiency microbial fertilizers. Tomato seeds were used as the experimental material in this study. Endophytic bacteria were isolated and purified from the seeds using the dilution spread plate method. The phylogenetic analysis of strains was done by partial 16S rRNA gene sequences. The promotion characteristics of the strains were assessed via CAS plate assays, inorganic phosphate plate assays, and the Salkowski colorimetric method. Additionally, a seed germination assay was conducted to evaluate the effects of indole acetic acid (IAA)-producing bacterial strains on tomato seed germination. The results of 16S rRNA gene sequence analysis revealed that nine isolated endophytic bacterial strains from tomato seeds belong to two genera: Enterobacter and Bacillus. The plant growth-promoting trait assays revealed that four strains possessed siderophore-producing ability, and three strains exhibited IAA production ability, among which strains B₂ and B₄ demonstrated higher IAA yields of 88.30 μg/mL and 69.31 μg/mL, respectively. Notably, both strains also exhibited the ability to dissolve inorganic phosphorus. Germination assays further confirmed that the fermented broth of strain B₄ significantly promoted tomato seed germination. This study enriches the tomato endophytic bacterial resource library, and the screened B₄ strain demonstrates potential as a plant growth-promoting resource for developing multi-functional microbial fertilizers.

Key words: endophytic bacteria, tomato seeds, isolation and identification, promotion characteristic, indole acetic acid (IAA), seed germination