Amrita Kasotia

Bacterial-Mediated Tolerance and Resistance to Plants Under Abiotic and Biotic Stresses

Plant growth-promoting bacteria (PGPB) are capable of alleviating environmental stress and eliciting tolerance in plants to promote their growth. Several PGPB elicit physical and/or chemical changes related to plant defense in the form of induced systemic resistance (ISR) under biotic stress. Researchers emphasized that PGPB-elicited ISR has suppressed plant diseases caused by a range of pathogens in both the greenhouse and field. PGPB-elicited physical and chemical changes in plants result in enhanced tolerance to drought, salt, and other factors that have been described as a form of induced systemic tolerance under abiotic stress. This review will focus on recent research concerning interactions between PGPB and plants under biotic and abiotic stresses. The use of PGPB requires precise understanding of the interactions between plant-bacteria, among bacteria-microbiota, and how biotic and abiotic factors influence these relationships. Consequently, continued research is needed to develop new approaches to ameliorate the efficiency of PGPB and to understand the ecological, genetic, and biochemical relationships in their habitat.

Molecular Mechanism of Benign Microbe-Elicited Alleviation of Biotic and Abiotic Stresses for Plants

In continuous agricultural systems, crop yields are directly dependent on the inherent soil fertility with microbial processes that governs the mineralization and mobilization of nutrients required for plant growth. The impact of different crop species that are used in various combinations is likely to be an important factor in determining the structure of plant benign microbial communities that function in nutrient cycling, the production of plant growth hormones, and suppression of root diseases. In the present scenario, a perceived role of biotechnology is to introduce multiple choreographed genes into plants that would elicit multiple benefits to the plants such as resistance to stress, productivity, and quality. Microbial genomes that have coevolved with native plant species may already be choreographed and compatible with a wide range of plant genomes and available in this vast unexplored genetic reservoir. Understanding of microbial genome and how it communicates with plant genome for their mutual welfare could lead to innovative methods of plant improvement. Increased adverse effects of abiotic and biotic stresses impacting productivity in principal crops are being witnessed all over the world. Extreme events like prolonged droughts, intense rains and flooding, heat waves, and frost damages are likely to further increase in future due to climate change. A wide range of adaptations and mitigation strategies are required to cope with such impacts. Efficient resource management and crop improvement for evolving better breeds can help to overcome abiotic stresses to some extent. However, such strategies being long drawn and cost intensive, there is a need to develop simple and low cost-effective biological methods for the management of abiotic stress, which can be used on long-term basis. Therefore, studies are needed to elucidate the molecular mechanisms that result from treatment of plants with benign microbes under stress conditions and only then will the full benefits of plant-microbe interaction be understood.

Microbial-Mediated Amelioration of Plants Under Abiotic Stress: An Emphasis on Arid and Semiarid Climate

It is consensus that plant growth-promoting bacteria (PGPB) be studied extensively in the last two decades, but several of them are not fully investigated/explored especially in arid and semiarid regions worldwide. They have been deployed as potent source of bioactive compounds useful in prospecting of sustainable agricultural. In the present scenario to meet food security, a number of different approaches have been employed to cultivate crops in salt- and drought-prone area. Hence, nowadays, the use of microbial inoculation to alleviate abiotic stress and amelioration of crops could be considered a more cost-effective eco-friendly approach. By keeping current approaches available for plant-microbe interaction, it is needed to pursue prospective research in this area. In the present chapter, authors will emphasize the role of benign PGPB in crop cultivation under stress through produced elicitors/determinants. It is very urgent need to explore this approach for sustainable agriculture grown under stress and also to understand the mutual interactive activities belowground. Therefore, an exploitation of PGPB-plant interactions may be opted in the amelioration of plant health in arid and semiarid area.

Chapter 5 – Plant Growth-Promoting Bacteria Elicited Induced Systemic Resistance and Tolerance in Plants

Plant growth-promoting bacteria (PGPB) are microorganisms that exert benign effects on plants and regulate plant growth. They are the denizen of rhizosphere and along with it form epiphytes (on plant surface) and endophytes (inside plant tissues) that define all the regulatory processes of plants including resistance and tolerance against biotic and abiotic stresses. Several PGPB induce resistance against pathogens by eliciting physiological changes in plants together with tolerance to drought, salt, and other environmental factors. Bacteria elicited induced systemic resistance and tolerance provides plants with stress-responsive mechanisms whereby they mitigate stresses to practical agriculture. Plants acquire an enhanced level of resistance/tolerance after exposure to biotic/abiotic stimuli provided by many different PGPB. The present chapter focuses on mechanisms implicated for bacteria-induced plant growth under biotic and abiotic stresses.

Chapter 4 – Role of Endophytic Microbes in Mitigation of Abiotic Stress in Plants

At the global level extensive research has been carried out with plants to develop tolerant varieties against abiotic stress by means of genetic engineering. In the present scenario, an alternative strategy has been developed where microbial endophytes have played a key role to the plant’s successful survival under abiotic stress. Endophytes employ mechanisms through which plants overcome abiotic stress; these include accumulation of stress-responsible molecules, secondary metabolites, and production of antioxidant enzymes. There are various reports wherein the interaction of endophytes with their host plants as symbiotic association have been elaborately described and such association with plants makes hosts tolerant under stresses. This chapter emphasizes the role of microbial endophytes in the mitigation of abiotic stress so that native and cultivated plants maintain sustainable agriculture.