Chapter 7 - Promoting crop growth with symbiotic microbes in agro-ecosystems—II

Abstract

The plant–microbe interactions depend upon the plant–microbe natural characterization and environmental factors, and plant–microbe symbiosis is captivated from both sides. Plants produce nutrients consumed by microbes for their requirements and microbes secrete useful substances for the growth and development of plants. Plant–microbe symbionts create a healthy and growing environment. Several algae, cyanobacteria, mycorrhizal fungi, diazotrophic bacteria, and actinomycetes live in a beneficial association with plants. The symbiotic microbes play an important role in biological activities such as nitrogen fixation, phosphate solubilization, ACC deaminase activity, the formation of phytohormones and siderophores, acquired antagonistic activity, etc. that boost plant growth promotion. Symbiotic nitrogen-fixing bacteria enhance the productivity of plants. The symbiotic association between rhizobium and leguminous plants is the most cooperative plant–microbe interaction. The cyanobacteria, including Nostoc and Anabaena, live in association with plants and Nostoc takes part in biological nitrogen fixation. The mycorrhizal association delivers phosphorus, nitrogen, potassium, and micronutrients to roots, protects from diseases, and promotes the rapid establishment of plants. One of the most significant associations between algae and fungi is where algae and fungi provide food and water to each other. Plants release root exudates containing sugar, vitamins, fatty acids, amino acids, enzymes, and inorganic volatile compounds that are used as substrates by microbes to gain a nutritionally enriched environment for their survival. These symbiotic microbes in turn become excellent sources of biofertilizers.