Delineating the foraging strategies for soil resources beyond the rooting zone of different arbuscular mycorrhizal fungi upon co-inoculation

Arbuscular mycorrhizal fungi (AMF) are crucial components of terrestrial ecosystems, yet their basic ecology with respect to their co-existence within plant-dominated environment remains poorly understood. This study compared root colonization and foraging behaviors of five AMF isolates from four families (Acaulosporaceae, Gigasporaceae, Entrophosporaceae, and Glomeraceae) when inoculated together. Additionally, we examined their impact on plant growth and nutrient uptake. The rate of root colonization and foraging within root-free patches of various quality was assessed by measuring absolute and relative abundances of the different isolates using taxon-specific quantitative real-time PCR markers and amplicon (WANDA-AML2) sequencing. Notable differences were observed in the colonization patterns of roots and root-free patches among the different isolates. Most isolates from the Glomeraceae family, specifically Rhizophagus irregularis and Funneliformis mosseae, exhibited the highest rates of root colonization and actively foraged for nutrients in the root-free patches, yet differing in their preferences. In contrast, isolates from other families showed limited development, primarily restricted to the roots and rhizosphere. Inoculating Andropogon gerardii with the AMF significantly increased uptake of ¹⁵N-labeled nitrogen from chitin and clover patches and reduced overall N losses from experimental microcosms. Furthermore, microbiome profiling revealed that presence of extraradical AMF hyphae systematically elevated abundance of certain microbes (possibly the AMF-associated taxa) such as Pseudoarthrobacter, Nocardioides, and Paraparentocirrus across the different patches. This research suggests that the colonization strategies of AMF species vary significantly at the family level and are influenced by labor partitioning upon exploration of soil patches of different qualities.