Exploration of Plant Growth Promoting Endophytes from Halophytic Flora for Sustainable Agriculture and Possible Mitigation of Salinity Stress

The growing population demands increased production of food crops. Modern agriculture is facing numerous challenges including urbanization, water scarcity, loss of soil integrity, climate change and biodiversity loss. In addition to these, soil salinity which has substantially increased over time due to the excessive use of fertilizers is raising concerns. The increased salinity of farming land hinders plant growth. Since the agricultural land on earth is limited, it is essential to protect that land from salinity stress and to promote crop development in affected soils. Halophytes are known for their ability to survive in hypersaline environments. They possess several mechanisms to prevent damage caused by high salt concentrations and to thrive well in such environments. Besides these mechanisms, like other land plants, they also host endophytes. These halophytic endophytes, much like other adaptive features, help halophytes in many ways to survive in harsh environments. The endophytes from these plants can be utilized as a promising supplement for supporting crop development in saline soils, as they are naturally exposed to challenging saline environments and contribute to the growth of both themselves and their host plants. The present study is an effort to identify plant growth promoting endophytes from halophytes for mitigating salt stress and promoting crop development by the seed coating method. Four halophytes from two different saline environments were selected for the study. The selected plants were identified as Rhizophora mucronata, Ceriops decandra, Ipomoea pes-caprae and Spinifex littoreus. Twelve morphologically distinct endophytes (designated as RR, RS, RL, CR1, CS, CL, SR, SS, SL, IR, IS and IL), isolated from roots, stems and leaves of these collected halophytes were characterized using conventional methods and sequencing techniques. They were then studied for their ability to promote plant growth and mitigate salt stress by analysing their salt tolerance (NaCl), phosphate solubilization, ammonia utilization, nitrogen fixation, IAA production, siderophore production and plant growth supporting enzymes. Then they were utilized as seed coats to support plant growth in Abelmoschus esculentus. All the selected isolates were identified to possess at least one plant growth promoting mechanism, and many tested positive for multiple traits. This shows that they can be effectively used in promoting plant growth in saline soils.