Abstract
Beneficial microbes are used as the best alternative against the synthetic fertilizers and pesticides. The beneficial microbes not only help with plant growth, nutrition uptake, nitrogen fixation, but also help in acquiring the ions, not freely available to plants to uptake; these microbes also guard the plants by secreting toxic chemicals by inducing defense systems against pathogens. These microbes can provide best choice to look forward to sustainable agriculture and sustainable ecosystem. The addition of soil inoculants in the form of microorganisms or bio stimulants promise more environmentally friendly approaches for augmenting crop yields. The crop becomes less reliant on chemical fungicides and herbicides as many strains of microorganism have abilities of controlling pests. In this chapter, the interaction of beneficial plant bacteria, bio stimulants, effects on native microbial communities, and bacteria influencing economically important crops are discussed.
TopBeneficial Microorganisms For Crop Plants
The use of chemical fertilizers and pesticides in agriculture unlocked the hurdles to combat food insecurity issues. With the advancement of science and research, it manifested that the use of these chemical inputs, in a long run, found as curse in disguise due to adverse health impacts to human and animals as well as in degradation of soil ecosystem. In this situation, the use of bio inoculants (beneficial microorganisms) is a hopeful option for having properties to fight against diseases, caused by various viruses, bacteria, nematodes, etc., and aggrandize the growth of plant (Pereg & McMillan, 2015). The growth of plant is depending on the soil type and the healthy plant-roots relationship, containing the soil microbial community. However, their association may give different response with different crop type, existing soil micro biota, geography, climatic conditions, bacterial strain and soil health.
The beneficial microorganism create association with plant roots which help to elevate nutrient uptake from soil by nitrogen fixation and reduced chemical fertilizers demand (Naik et al., 2019), potassium and phosphate solubilization and clampdown of pathogens, hence increase the agronomic productivity (Romano et al., 2020). These associational benefits are naturally evolved and may get benefits from a single microbial community or a consortium (Naik et al., 2019). The use of beneficial microorganisms make rhizosphere good in physical and chemical composition with longstanding fertility, maintaining healthy soil, combating framing costs and ensures sustainability (Debnath et al., 2019). Many species and strains of bacteria, fungi, yeast and actinomycetes are used as bio-inoculants. The most widely used bioincoulants are plant growth-promoting (PGP) microbes and bio-control agents.
The plant-growth promoting bacteria (PGPBs) are involved in such symbiotic association which produces that kind of metabolites which make the process of P solublization, N2 fixation, pathogens inactivity, and siderophores and phytohormones production, effortless for plant. In return the only thing the PGPBs get from plant is their energy essential carbohydrates (Nion, 2015; Saad et al., 2020; Sivasakthi et al., 2014). The extracellular matrix, exopolysaccharide are released by bacteria for the protection of its cell from toxic components and dehydration. These exopolysaccharides have cementing characteristics. Plants take advantage by bio-filming these exopolysaccharides which bind soil aggregates, fix nutrients and support water movement through roots (Meneses et al., 2017; Saad et al., 2020). The success of applied PGPB in agricultural crops is affect by the bacterial colonization with root, soil health and diffusion across plant roots and soil (Beauregard et al., 2013; Carvalhais et al., 2013). However, to select applicable PGPBs, following points must be considered; PGPBs should be according to regulatory agencies of country to ensure safe release and environmental safety, confirm the fitness of PGPB strain to efficient biological activity, selection to their particular environmental conditions (like organism working well in cold environment versus those well adopted for hot environment), the relationship of endophytic and rhizospheric bacteria in soil and the detailed associational analysis of PGPB with existing soil microbes and mycorrhizae (Glick,2012). Looking forward to sustainable agriculture, many strains of Bacillus and Pseudomonas sp. are used and are under screening to be used in treatment of heavy metal eradication, salinity problem and enhancing the drought tolerance of plant under water stress regions (Singh et al., 2018).
Key Terms in this Chapter
Pattern Recognition Receptors: They are the proteins used for recognition of molecules found frequently in pathogens or the molecules which are released by damaged cells.
Actinomycetes: Unicellular gram positive bacteria found in a variety of habitats.
Bio-Control Agent: It is the living organism/biological agent which is utilized for controlling insect pests. In other words they are natural enemies of crop pests.
Siderophore: It is an iron chelating compound produced/secreted by microorganisms and helps to transport iron across cell membranes.
Diazotrophs: Bacteria and archaea that are capable of converting atmospheric nitrogen gas into more usable form (ammonia). They are grown without external sources of fixed nitrogen.
Bio-Fertilizer: It is a type of fertilizer comprising of living organisms, which when applied to the plants, soil colonizes and promote plant growth wellbeing by providing them with primary nutrients.
Endophytic Bacteria: Type of bacteria that lives inside plants and improve the plant growth, health and development under normal as well as challenging conditions.