Influence of Endophytic Bacteria on Growth Promotion and Protection against Diseases in Associated Plants

Plants are colonized by different endophytic microbial communities. These endophytic microbiomes have been reportedly associated with improved growth, metabolism and defence against other physical factors. The endophytic population varies with plant species, genotypes and crop growth stages. They contribute plant growth promotion through nitrogen (N) fixation, phosphate solubilization and phytohormone production. Several phytohormones, such as indole-3-acetic acid (IAA), gibberellins (GA) and cytokinins (CK), synthesized by the plant endophytes can enhance different stages of plant growth, such as root formation, stimulation of cell division, extension, differentiation and regulation of fruit ripening. The low-molecular-weight siderophore molecules produced by these endophytes show high affinity for ferrous iron. Endophytes aid in the host’s survival against biotic stress by the production of HCN and secondary metabolites that suppress the soilborne pathogens. They also enhance plant fitness by producing novel bioactive compounds. Different kinds of alkaloids produced by the endophytes also provide resistance to plants against environmental stresses. The amines and amides produced by the plant endophytes have shown toxic effects to insects. The endophytic bacteria can trigger strawberry flavour. Advanced techniques, such as metagenomics based on next-generation sequencing is useful to study the taxonomical diversity of microbial communities associated with the economically and agriculturally important crops. This chapter reviews the important role of plant-associated bacterial endophytes in agricultural crops.