Establishment of seed biopriming in salt stress mitigation of rice plants by mangrove derived Bacillus sp.

Salinity stress is one of the growing challenges for agro-ecosystems. Present study aimed to explore the role of halotolerant bacteria in alleviation of salinity stressed rice plants. Bacillus sp. strain PnD was isolated from Indian Sundarban Mangrove Forest, conferred plant growth promoting (PGP) traits like indole 3-acetic acid (IAA) production, phosphate solubilization, siderophore production but had negative effect of 1-aminoacyclopropane 1-carboxylate (ACC) deaminase activity. Rice seeds (Oryza sativa L.) of Amal-Mana variety were subjected to salinity stress for 24 h by being immersing in 1% NaCl. Another set of seeds were soaked in a broth cultured with Bacillus sp strain PnD, containing 1% NaCl in the media, denoted as bioprimed condition. The seeds that were soaked in distilled water had no salt stress and were not primed, served as control. All the treatments were assigned randomly to the seeds and each treatment was replicated three times resulting in nine experimental units. Completely randomized design was adopted in this experiment. Overall results showed bioprimed seeds soaked in 1% NaCl for 24 h had significantly higher germination percentage, seedling growth, photosynthetic pigments content compared to control and non-primed salinity exposed plants. Scanning electron micrograph revealed root colonization of bacteria in bioprimed seedlings, tissue distortion was also noted during salt stress. The study revealed that Bacillus sp. strain PnD is a potential plant growth promoting bacterium (PGPB), and the seed biopriming technique can efficiently mitigate inhibitory effects of salinity stress in rice plants.