Bacterial inoculation prevents cold-induced electrolyte leakage from tomato seeds and reduces thermal fluctuations in the rhizosphere.

Abstract

Background: Low soil temperature and its fluctuation can negatively impact the growth of seedlings. The district of Cooch Behar (India), belonging to the Cwa zone (according to Koppen's classification), receives several cold waves during winter. Our previous study demonstrated that a constant temperature of 20 °C (chilling but not freezing) can cause a loss in the vigor of tomatoes. Since the temperature of the soil is not uniform throughout the day, we hypothesized that the duration of cold exposure can have variable effects on seed vigor.

Results: It was observed that increasing the duration of cold stress can slow down the germination process and reduce vigor. This was due to the cold-mediated damage to cell membranes (due to dehydration) which caused electrolyte leakage and reduced levels of glutathione reductase. In this regard, biopriming seeds with microbes that produce exopolysaccharide (EPS) can be useful as it can form a protective layer on the seeds. Indigenous EPS-producing bacteria, Bacillus, Phytobacter and Priestia sp., were used for biopriming. Priestia and Phytobacter sp. not only reduced the electrolyte leakage but also increased the levels of antioxidant genes. This improved the germination speed and vigor. In a field trial, the rhizosphere of the seedlings pretreated with bioinoculants displayed a reduced thermal fluctuation compared with the untreated seeds.

Conclusion: The seedlings treated with bioinoculants grew faster in soil in spite of low soil temperature. This can reduce the nursery time of seedlings. © 2025 Society of Chemical Industry.