Soil conditions regulate the patterns of root colonization by fungal endophytes in Guinea grass ( Megathyrsus maximus )

Dark Septate Endophytes (DSE) and Arbuscular Mycorrhizal Fungi (AMF) are two types of endophytic fungi that have a mutually beneficial relationship with plants. This relationship is known to be influenced by various environmental factors. It has been reported that native grasses in semi-arid grasslands are extensively colonized by DSE compared to AMF, but there is limited information available for introduced grasses. Therefore, in this study, we aim to analyze the relationship between a non-native invasive grass, Megathyrsus maximus (Guinea grass), and the two endophytes, as well as the influence of soil variables on this relationship. Our analysis of root and soil samples collected from 150 locations in South Texas revealed that M. maximus is heavily colonized by both endophytes, and this relationship is influenced by soil moisture levels. Specifically, M. maximus showed a higher degree of AMF root colonization (85%) in areas with high soil moisture (20–25% soil moisture), while it had a higher degree of DSE colonization (75%) in areas with lower soil moisture conditions (0–5% soil moisture). Our results suggest that M. maximus benefits from its mutualistic relationship with fungal endophytes in semi-arid ecosystems in its introduced range, and this relationship could aid in the invasion of new habitats.