The influence of plant growth-promoting rhizobacteria in plant tolerance to abiotic stress: a survival strategy

Abstract

Action is needed to face the global threat arising from inconsistent rainfall, rise in temperature, and salinization of farm lands which may be the product of climate change. As crops are adversely affected, man and animals may face famine. Plants are severely affected by abiotic stress (drought, salinity, alkalinity, and temperature), which impairs yield and results in loss to farmers and to the nation at large. However, microbes have been shown to be of great help in the fight against abiotic stress, via their biological activities at the rhizosphere of plants. The external application of chemical substances such as glycine betaine, proline, and nutrients has helped in sustaining plant growth and productive ability. In this review, we tried to understand the part played by bioinoculants in aiding plants to resist the negative consequences arising from abiotic stress and to suggest better practices that will be of help in today’s farming systems. The fact that absolute protection and sustainability of plant yield under stress challenges has not been achieved by microbes, nutrients, nor the addition of chemicals (osmo-protectants) alone suggests that studies should focus on the integration of these units (microbes, nutrients, chemical stimulants, and osmo-protectants) into a strategy for achieving a complete tolerance to abiotic stress. Also, other species of microbes capable of shielding plant from stress, boosting yield and growth, providing nutrients, and protecting the plants from harmful invading pathogens should be sought.

Bacillus subtilis ameliorates water stress tolerance in maize and common bean

“…According to Lastochkina et al (2017), B. subtilis promotes plant growth and increases plant stress tolerance through of direct and indirect ways, such as synthesis of siderophores and/or plant hormones and improvement of nutrient availability. Furthermore, it is related that plants associated with PGPR display better relative water content, especially in abiotic stress situations (Parray et al 2016;Enebe and Babalola 2018). Indeed, common bean and maize inoculated with B. subtilis showed highest relative water content than non-inoculated plants under water stress.…”

“…Double asterisk (**) indicates significant differences between control and water stress in each treatment (Tukey's test, p < .05). (You and Chan 2015;Ngumbi and Kloepper 2016;Enebe and Babalola 2018). According to Brilli et al (2019), PGPR might improve plant performance in abiotic stress situations through maintenance of a ROS level compatible with cellular functioning.…”

“…Some bacteria belonging to the genera Azotobacter, Bacillus, Klebsiella, Pseudomonas, Azospirillum, and Serratia are beneficial microorganisms recognized as plant growth-promoting rhizobacteria (PGPR) (Figueiredo et al 2016;Parray et al 2016). PGPR are microbes that promote beneficial effects on plant development through direct or indirect mechanisms (Ngumbi and Kloepper 2016;Enebe and Babalola 2018). Nutrient acquisition, synthesis of phytohormones, production of siderophore and improvement of antioxidant system are direct mechanisms performed by PGPR (Parray et al 2016).…”

Genome Insights of the Plant-Growth Promoting Bacterium Cronobacter muytjensii JZ38 With Volatile-Mediated Antagonistic Activity Against Phytophthora infestans

“…Plant growth and abiotic stress tolerance promotion by bacteria is well established (Dimkpa et al, 2009;Glick, 2012), but the precise mechanisms are still not fully understood. However, there are numerous indications that bacterial phytohormone production, such as IAA, can play important roles (Patten and Glick, 2002;Enebe and Babalola, 2018). Production of IAA occurs through five different pathways using tryptophan (Trp) as a precursor: indole-3-acetonitrile (IAN), indole-3-acetamide (IAM), tryptophan side-chain oxidase (TSO), tryptamine (TAM) and indole-3-pyruvate (IPyA) pathways (Patten and Glick, 1996;Carreño-Lopez et al, 2000;Spaepen et al, 2007).…”

Bacterial Diversity and Community Structure in Typical Plant Rhizosphere

“…Under unfavorable conditions, plant-growth-promoting rhizobacteria alleviate the effects in plants of such parameters as germination rate, drought tolerance, and plant yield components. The use of microorganisms in agriculture for crop protection against plant pathogens and pests because of the metabolites they produce, and also biological control against diseases, may present an alternative for plant disease prevention [9,10].…”