Uncovering the hidden underground associations of weeds with arbuscular mycorrhizal fungi and dark septate endophytes

Understanding the factors that influence weed ecology and their competitive capacity is essential for developing efficient weed management techniques. One important factor that affects the growth and competitiveness of plants is their ability to associate with mutualistic microorganisms. Thus, a survey to evaluate the presence of arbuscular mycorrhizal fungi (AMF) and the occurrence of dark septate endophytes (DSE) in the roots of 46 weed species from 24 families, naturally growing in an agricultural area in Viçosa, MG, Brazil, was carried out. Most of the weed species (45) were colonized by AMF, while only 12 (26%) formed associations with DSE. Most plants showed root colonization percentages by AMF greater than 70%. Vesicles were present in 24 species, whereas arbuscules were present in 44. We have also checked the occurrence of the weed species reported here across Africa, America, Asia, Europe, and Oceania, and verified that they were widely distributed. More than 80% of the sampled weed species were also reported in at least one country in Africa, the Americas, and Asia. Furthermore, approximately 59% of the weed species analyzed were reported to occur in all continents. Here, we have made the first report of the occurrence of AMF associations in 13 weed species, corroborating the importance of weeds for maintaining soil AMF inoculum potential. Future research must be done to determine whether AMF or DSE associations can improve the competitive ability of these plants against crops or vice-versa, opening new avenues for sustainable integrated weed management.