Mycorrhiza. Mycorrhiza is a symbiotic association of fungi with roots of plants so that the nutrients absorbed from soil by the fungi are released to the host cells and in turn, the fungus takes its food requirements from the host. Mycorrhizae are of two types: (i) ectomycorrhizae, and (ii) endomycorrhizae. Ectomycorrhizae and found on the roots of forest trees (e.g. pine, oak, beech, phosphorus, potassium and calcium. They also convert complex organic molecules into simpler available forms, protect the roots from the pathogens, and produce growth promoting substances (cytokinins).

Endomycorrhizae are found in the roots of most fruits and other horticultural crops (e.g. coffee, pepper, cardamom, and betel vine). They particularly help in phosphorus nutrition. They also produce growth promoting substances and offer resistance against pathogens. The seedlings in nurseries are inoculated with endomycorrhizae and then transplanted in the field as done by citrus growers in USA. Strains belonging to genera Azotobacter, Aspergillus, Azospirillium, Beijerineleia, and Glomus are used as endomycorrhizae.