Insights into the multifaceted roles of soil microbes in mitigating abiotic stress in crop plants: A review

Abstract

Abiotic stresses, including thermal extremes, water scarcity, metal toxicity, and high salinity levels, pose significant challenges to agricultural sustainability and food security. These stresses, driven by climate change, soil degradation, and pollution, disrupt water and nutrient uptake, photosynthesis, and cellular integrity. Consequently, plant growth, production, and yield are significantly reduced, highlighting the need for sustainable techniques, like utilizing soil microbes, which is crucial for effectively alleviating abiotic stress in plants. Microbial inoculation, particularly with arbuscular mycorrhizal fungi (AMF) and plant growth-promoting bacteria (PGPB), significantly mitigates these stresses. These microorganisms enhance plant growth, nutrient uptake, and stress tolerance through mechanisms like nutrient solubilization, polyamine accumulation, and reactive oxygen species (ROS) scavenging. They improve plant physiological responses, such as photosynthesis rates and stomatal conductance, and contribute to ultrastructural stability by maintaining membrane integrity and promoting the accumulation of osmolytes like trehalose, proline, polyamines (PA), and glycine betaine (GB). The activation of antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) further reduces oxidative stress. Key signaling pathways, including the Mitogen-Activated Protein Kinase (MAPK) cascade and Salt Overly Sensitive (SOS) signaling, play critical roles in plant responses to osmotic and ionic stresses. Additionally, aquaporins (AQPs), Calcium-Dependent Protein Kinases (CDPKs) and Late Embryogenesis Abundant (LEA) proteins are integral to abiotic stress resistance. Microbial symbiosis enhances these pathways, promoting ion homeostasis and stress resilience. Overall, understanding the intricate interactions between plants and soil microbes, coupled with sustainable agricultural practices, is crucial for enhancing crop resilience to abiotic stresses and ensuring food security amidst climate change. This review paper emphasizes the detrimental impacts of abiotic stresses on agricultural sustainability and food security, highlighting the imperative for sustainable techniques like utilization of soil microbes to effectively mitigate these stresses and enhance crop resilience.