BackgroundLow 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 degrees 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.ResultsIt 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.ConclusionThe seedlings treated with bioinoculants grew faster in soil in spite of low soil temperature. This can reduce the nursery time of seedlings. (c) 2025 Society of Chemical Industry.

Unlike the Himalayas, the sub-Himalayan zones did not experience snowfall and thus suitable for growing solanaceous vegetables. However, several cold waves have been reported to affect the district of Coochbehar (West Bengal, India), which belongs to the Cwa zone (as per Koppen's classification). Variable duration of sub-optimal soil temperature can have a detrimental effect on the growth of seedlings. Our previous study demonstrates that a constant temperature of 20 degrees C (6 degrees below the optimal soil temperature) causes a 71% loss of vigor in seeds of solanaceous plants. Since the soil temperature is not constant diurnally, it was hypothesized that the duration of cold stress can have variable effects on vigor of Capsicum annuum L. It was observed that increasing the duration of cold stress (18 degrees C) up to 2 hours/day can improve the vigor but after 6 hours/day, a significant drop in vigor was observed. This was because of the cold-associated membrane damage leading to the leakage of electrolytes. To date, this stress existing in these regions has gone unnoticed. In this regard, biopriming the seeds with exopolysaccharide (EPS)-producing microbes can be useful as the EPS can form a protective layer on the seeds. Two lesser-known bacteria namely, Phytobacter and Priestia sp. were evaluated for their vigor-recovering ability. Treatment of seed with these microbes reduced the electrolyte leakage which improved the vigor under sub-optimal stress. This was also validated by fluorescent microscopy. Both these strains displayed an enhanced EPS-producing ability at 18 degrees C which correlated with the reduced electrolyte leakage and enhanced stability of cell membrane. Such bacteria can help in promoting seed vigor under sub-optimal temperature stress. Bacterial inoculation prevents cold-induced membrane damage in seedlings.