Bacterial Endophytes and Their Contributions to Alleviating Drought and Salinity Stresses in Wheat: A Systematic Review of Physiological Mechanisms

Abstract

Drought and salinity stresses significantly threaten global wheat productivity, limiting growth and reducing yields, thus endangering food security worldwide. These stresses disrupt physiological processes, impair photosynthesis, and hinder optimal growth and yield by diminishing water uptake, causing osmotic stress, ion toxicity, and oxidative stress. In response, various mitigation strategies have been explored, including breeding for stress-tolerant cultivars, improved irrigation techniques, and the application of exogenous osmoprotectants and soil amendments. Among these strategies, the emergence of rhizospheric and endophytic growth-promoting microorganisms has attracted significant attention. Therefore, a systematic review was undertaken to illustrate the role of endophytic bacteria in enhancing wheat tolerance to drought and salinity stresses. This review analyzes physiological mechanisms and research trends, identifies gaps, and discusses implications for sustainable agriculture. An analysis of the literature related to endophytic bacteria in wheat was conducted using databases of major publishers from 2004 to 2023. The review explores their mechanisms, such as phytohormone production and stress-responsive gene induction, emphasizing their contribution to plant growth and stress resilience. The current research trends indicate a growing interest in utilizing endophytic bacteria to mitigate these stresses in wheat cultivation, with studies focusing on understanding their physiological responses and interactions with wheat plants. Future research should concentrate on elucidating the role of endophytic bacteria in enhancing host plant tolerance to multiple stressors, as well as aspects like endophytic mechanism of action, endophytic lifestyle, and transmission pathways. Overall, endophytic bacteria offer promising avenues for sustainable agricultural practices, aiding in crop resilience and food security amid environmental challenges.