Arbuscular mycorrhizal fungi as biofertilizers: Current trends, challenges, and future prospects

The global food production will need to be increased by twofold by 2050 in order to feed the increasing human population while incurring minimal pressure on the remaining arable lands. The synthetic chemical fertilizers used in agriculture have lost their luster due to many environmental consequences. The use of biofertilizers in place of chemical fertilizers has long been identified as a healthier approach to lessen some of the environmental consequences and to maintain sustainability in agriculture. There are much evidence to suggest that the use of beneficial microbes increase the soil productivity and the quality of the produce, while decreasing environmental costs. Of many microbial contenders, arbuscular mycorrhizal fungi (AMF) have shown promising potential to be used as a biofertilizer due to its numerous benefits. AMF can enhance plant growth through their contribution in facilitating the uptake of nutrients and water, creating plants resistant to soilborne diseases, and helping their host to endure adverse conditions. In addition, AMF could also play a role in controlling soil erosion, remediating soil pollutants, and eradicating harmful organisms. AMF have even shown a greater potential to be used as a biofertilizer to improve the initial growth and establishment of tree seedlings in restoration projects. Despite its long history as a potential biofertilizer, farmers still show some reluctance to use them even with reduced dosages of chemical fertilizers. The main reason seems to be the difficulty in transforming the success stories of AMF under glasshouse conditions to real farmer fields. However, currently this AMF industry faces many challenges owing to inconsistent outcomes, issues related to tracking the inoculant success in the field, knowledge gaps and lack of methodology for large-scale production of inoculants, and quality control. New technologies such as next-generation sequencing (NGS) provide insight into how AMF interact with indigenous counterparts and to screen beneficial microbial candidates with specific functional traits. Rather than using individual isolates, the use of effective AMF communities may stand better chances to mitigate some drawbacks under field conditions. With new technologies in place, the researcher need to focus more on classifying diverse pool of AMF species based on their host and environmental preferences, with the aim of defining the best inoculum for different crops and climatic conditions. The technologies and protocols related to the preparation of effective inocula and to maintain quality control of products are also critical to commercialize AMF inoculants to meet the needs of the farmers. An effective formulation of biofertilizers not only increases its population in soil, but also maintains its stability while increasing the inoculation potential and activity. Once these challenges are addressed, AMF has a greater potential as a biofertilizer in agriculture, in the tropics in particular, which is facing a grim future at present due to the ever-increasing cost of chemical fertilizers, environmental and health consequences, and climate change.