The Interactions of Soil Microbes Affecting Stress Alleviation in Agroecosystems

Abstract

Crop plants are subjected to different kinds of stresses, and as a result, their growth is adversely affected. Different mechanisms may be used by crop plants to tolerate the stress including the morphological and physiological ones. However, the efficiency of such mechanisms differs in sensitive and tolerant crop species, and the tolerant species can utilize such mechanisms more efficiently. The other important aspect of stress tolerance in crop plants is related to their interactions with the soil microbes. A wide range of soil microbes including arbuscular mycorrhizal (AM) fungi, plant growth-promoting rhizobacteria (PGPR), and endophytic bacteria as well as their interactions can affect stress tolerance in crop plants. Such a topic is among the most important research subjects and can greatly affect the efficiency of crop plants under stress. Mycorrhizal fungi are soil fungi, developing a symbiotic association with their nonspecific host plants, and increase their growth by enhancing the uptake of water and nutrients. PGPR are soil bacteria, which can enhance the growth of their host plant by different mechanisms through developing a nonsymbiotic association. The endophytic microbes are able to colonize the inner parts of their host plant and affect its growth under different conditions including stress. The interactions of soil microbes in most cases can positively affect the growth of the host plant under different conditions including stress. The important point, which deserves investigation, is the interaction of mycorrhizal fungi, PGPR, and the endophytic bacteria, which reside in plant roots affecting plant growth and yield production. Such details will be useful for the production of more tolerant microbial inoculums, which are more efficient under different conditions including stress. Some of the most important and recent findings related to the growth of crop plants under stress, as affected by the interactions of soil microbes, along with the future perspectives are presented, reviewed, and analyzed.