Production Methods of Arbuscular Mycorrhizal Fungal Inoculum: Challenges and Future Perspectives

Arbuscular mycorrhizal fungi (AMF) are widely known to improve plant and soil health by forming an obligate symbiotic relationship with most terrestrial plants. AMF biofertilizers can significantly reduce the need for synthetic inputs. The contribution of AMF to crop yield enhancement and ecological services is widely documented. Apart from agriculture, AMF applications have also found a significant position in forestry, agroforestry, horticulture, and restoring natural ecosystems. AMF promote soil aggregation, sequester soil C, and improve soil health by modifying the physical and nutritional state of the rhizosphere. Considering soil salinization and heavy metal pollution, AMF could act as bio-ameliorators. The production of AMF biofertilizers is challenging due to their obligate symbiotic nature which requires the presence of actively growing plant roots to complete their life cycle. AMF infectious propagules include arbuscules, spores, vesicles, and hyphae (intraradical and extraradical). Each of these can infect a plant and be used for AMF production. Several methods have been introduced to mass-produce AMF such as hydroponics, aeroponics, substrate-based, on-farm, and in vitro techniques. Substrate-based and on-farm production are simpler, while in vitro method ensures contamination-free inoculum. Hydroponics and aeroponics do not need a substrate but require a complex setup. The mass multiplication of AMF is widely attempted across the globe, but its success is a determinant of numerous factors that are often overlooked. This chapter tries to elucidate the various AMF inoculum production processes and their influencing elements. In addition, attempts have been made to comprehend how AMF inoculum could be adapted to a variety of crops and soil types to increase the benefits received from AMF in sustainable agriculture.