Plant productivity determinants beyond minerals, water and light: Piriformospora indica - A revolutionary plant growth promoting fungus

Biotic factors, along with the more obvious abiotic factors, determine and greatly influence the productivity and health of the plants. Arbuscular mycorrhizal fungi, AMF, the root-interacting predominant microbiota play an indispensable role in upgrading plant growth vigour and survival. However, the non-availability of the axenic culture is a great bottleneck for the fundamental studies and their biotechnological applications. Piriformospora indica is a newly described axenically cultivable phytopromotional endosymbiont, which mimics the capabilities of AMF. The fungus having a broad host spectrum shows pronounced growth-promotional effects. It mobilizes the insoluble phosphates and translocates the phosphorus to the host in an energy-dependent process. As a biological hardening agent of micropropagated plants, it renders more than ninety per cent survival rate for laboratory to field transferred plantlets. The successful isolation of regenerative protoplasts of P. indica opens up important possibility of improving symbiosis by transgenic manipulation of fungal component in a symbiosis-specific manner. The immobilization of the fungus stabilizes the infective capacity of the fungus and promises its use as a viable inoculum for biotechnological applications and long-distance transportation. The axenic cultivability of P. indica on economically viable synthetic media makes it suitable for mass scale inoculum production for application in agro-forestry and horticulture. In sum up, solar energy, water and soil nutrients are undoubtedly essential for plant productivity but the interaction with useful and friendly microbes also exert a tremendous impact.