Arbuscular mycorrhizal fungi as natural biofertilizers: current role and potential for the horticulture industry

摘要

Plant roots host a wide range of microorganisms that, together with the quality of soil and climatic conditions, represent the main factors that influence plant health, growth and development. Some microorganisms can facilitate use of soil fertility and optimize plant growth to a point that they are considered natural biofertilizers. In this context, mycorrhizae are mutualistic partnerships between fungi that live in soil and the roots of most terrestrial plants. A key role in plant health is playedby the obligate mutualistic arbuscular mycorrhizal fungi (AMF). These fungi can bridge the host roots to distant portions of undepleted soil, providing water and mineral nutrients to the plant. In addition, they promote pathogen protection via spatial competition and other more complex mechanisms. This is in exchange for photosynthetic products that are transferred to the fungus. They can symbiotically interact with more than 90% of vascular plant families, including important crops and woody ornamentals. Therefore, AMF are primary biotic soil components that, when missing or impoverished, can lead to a less efficient ecosystem functioning. Most of conventional agricultural practices can exert strong selective pressure on AMF, remodel community structure and reduce species diversity. This is a drawback for agriculture because the loss of AMF diversity can result in fewer functional traits from which the host plant can benefit. Needless to say, AMF have attracted a great deal of interest from the agricultural world over the years. In this context, these fungi have assumed a primary role in the development of a sustainable agriculture, which is based fundamentally on the limitation and partial replacement of chemical fertilizers and pesticides mediatedby the respect of natural microbiological balances. Many studies have investigated the positive effects of AMF inocula on the growth of an array of horticultural crops and model plants. Fewer studies have investigated the effects of AMF inoculation in floricultural species. There is a growing interest in reducing phosphorus inputs using AMF inocula; however the absence of solid inoculation practices and of large-scale trials with cost-benefit analysis regarding AMF application still represents a majorobstacle to the stable introduction of AMF into cultivation protocols. In this paper, we review the literature on AMF application in agriculture focusing specifically on horticultural and ornamental crops. We advocate that applied research will have to focus on classifying a diverse pool of AMF species according to their host and environmental preferences, on defining the best inoculum formulation strategies and application methods suitable for different conditions (e.g., open-field, greenhouse, transplant stage, in vitro propagation stage, urban green, etc.), and on imparting best-management practices to nurserymen, directing them to the solutions that most suit their conditions.