Biopriming with EPS-producing Bacteria of Sub-Himalayan-Soil Origin Recovers the Cold-Induced Vigor Loss in Seedlings

The eastern sub-Himalayan region of India (which belongs to the Cwa zone in Koppen’s classification) experiences severe cold waves during winter which causes a loss in seed vigor. Though most of the studies on cold stress deal with atmospheric temperatures, the seed vigor is majorly affected by the temperature of the soil. Therefore, the vigor loss of tomato and green gram were investigated under low-temperature stress. The analysis of locally available soil temperature showed a median value of 20.3 ± 0.1 °C. When the seeds were subjected to this temperature in vitro, a loss in vigor (70–75%) was observed. This was due to the reduced fluidity of the membrane which caused electrolyte leakage. In this regard, the indigenous polysaccharides-producing microbes act as an eco-friendly priming agent to recover the lost vigor. However, seed treatment with Bacillus and Pseudomonas strains didn’t affect the germination-related factors but aided in recovering 30–70% of the lost vigor by enhancing the growth of seedlings. The mode of vigor recovery was the production of indole-acetic acid. This approach can be used to quicken the nursery period of tomato and green gram exposed to low soil temperatures prevalent in the sub-Himalyan terai region.