Benefits of seed biopriming by PGPR and their mechanisms involved in increasing the tolerance of plants to abiotic stresses

Abiotic stresses reduce the yield of crops and their losses are expected to increase due to global climate changes. Seeds as vital inputs in agriculture are affected by various biotic and abiotic factors that may interfere with the natural process of seed germination. Priming is a process that helps to accelerate seed germination, improves the establishment and high seedling vigor, and results in higher plant yield, especially in adverse soil conditions. However, its effectiveness varies greatly at different stresses depending on the priming methods and factors. Seed biopriming, which involves the use of biological agents for priming, is a useful method for improving the viability, increasing the seeds germination, rapid and uniform emergence of seedlings in various abiotic stresses, and is also of great importance in dealing with biological stresses. One of the useful strategies that have become very important in recent years in the management of abiotic stresses is the use of plant growth-promoting rhizobacteria (PGPR) in seed biopriming. PGPR increase plant tolerance to abiotic stresses through various mechanisms and improve their growth and yield. These mechanisms include the production of ACC deaminase enzyme to reduce ethylene levels in plant roots, Modifying the content of phytohormones, inducing the synthesis of plant antioxidant enzymes, improving the absorption of nutrients required by the plant, Production of extracellular polymeric substance, reducing the uptake of heavy metals or excess nutrients by plants, Ion homeostasis in plants, accumulation of osmolyte during stress and the inducting resistance genes to abiotic stresses. It seems that the application of PGPR in seed biopriming is a suitable strategy in the sustainable increase of plant growth and coping with various stresses. This review article describes such mechanisms of action in more detail.).

Keywords:

Priming , ACC deaminase , Exopolysaccharide , Plant hormones , Ionic homeostasis , Antioxidant enzymes , Stress management