<i>Priestia</i> and <i>Phytobacter</i> sp. prevent membrane damage and electrolyte leakage from <i>Capsicum annuum</i> L. seeds subjected to sub-optimal temperature stress

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°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 °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°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.