Transition to agroecology promotes mutualistic and reduces antagonistic fungi in lettuce roots

Abstract Efficient and sustainable food production constitutes a significant challenge. Conventional agriculture involves the regular application of pesticides and fertilizers, with a wide range of negative externalities including the compromise of ecosystems stability, pernicious effects on human health, and social problems. These practices may negatively affect soil microorganisms including two groups of widely distributed plant root mutualists: arbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi (DSEF). These fungi improve host plant nutrition and growth, and protect them against stress. Agroecology has emerged as a demand for a paradigm shift in productive systems and involve the reduced or null inputs of agrochemicals that are replaced by ecological services provided by biodiversity and biotic interactions. Notwithstanding, the knowledge on how agroecological practices affect crops interactions with belowground mutualists and antagonists is limited. In this study, we evaluated through direct observation and molecular methods, the abundance and diversity of mutualistic -AMF and DSEF- and the abundance of antagonistic fungi Olpidiaster brassicae (ex Olpidium ) in lettuce roots cultivated in transition to agroecology (TA) and conventional horticulture (CH) fields located in central Argentina. We found that TA, mainly through avoiding agrochemical applications, increased root colonization levels of AMF and DSEF, molecular sequences abundance of AMF, and diversity of both mutualists while decreased percentage of colonization of the pathogen O. brassicae in lettuce. Therefore, through their effects on soil fungi, agroecological managements could benefit plant growth and health.