Arbuscular Mycorrhizal Fungal Associated to the Roots on the Common Bean and Their Agricultural Effect Under Different Environmental Conditions

Although many plant families are predominantly mycorrhizal, few symbiotic relation-ships between plants and arbuscular mycorrhizal fungi (AMF) have been thoroughly studied. Mycorrhized plants tend to exhibit greater tolerance to soil-borne pathogens and enhanced plant defence. Legumes, including common bean (Phaseolus vulgaris L.), are es-sential sources of protein globally. To improve common bean productivity, identifying ef-ficient native microsymbionts is crucial. This study aimed to identify native AMF associ-ated with common bean roots that could act as biostimulants and protect against soil diseases under varying environmental conditions. Agronomic trials were conducted at MBG-CSIC (Pontevedra, Spain) in 2021 and 2022, testing combinations of nitrogen fertili-zation, Burkholderia alba, Trichoderma harzianum, and a control. Traits such as nodulation, biomass, plant vigour, disease severity, nutrient content, and yield were evaluated. Four AMF species across three genera were identified. No consistent pattern was observed in AMF influence on agronomic traits. However, reduced mycorrhization in 2022 was asso-ciated with decreased nodulation, likely due to higher temperatures. Surprisingly, yields were higher in 2022 despite lower colonization. These findings suggest that intelligent use of AMF could reduce pesticide use, enhance sustainability, and promote healthier food systems. Continued research and conservation efforts are essential to optimize their bene-fits in legume production.