Plant interactions with arbuscular mycorrhizal fungi have long excited interest for their potential to promote more efficient use of mineral resources in agricultural production. Their use, however, remains limited, in part because of a lack of understanding of the factors that determine symbiotic outcome. In this work, variation in response to arbuscular mycorrhizal colonization was characterized a panel of genetically diverse maize inbred lines. The parents of the maize Nested Association Mapping population were evaluated, with and without colonization, in early vegetative stages. Subsequently, six lines with contrasting phenotypes were selected for further characterization, including quantification of fungal colonization, mycorrhiza-mediated phosphorus uptake, and accumulation of transcripts encoding plant PHT1 family phosphate transporters. The relative growth of lines changed between non-inoculated and inoculated plants, indicative of variation in host capacity to profit from symbiosis. Patterns of Pht1 transcript accumulation varied among lines, and were correlated with outcome. Larger growth responses were correlated with more extensive development of root-external hyphae, increased accumulation of specific Pht1 transcripts and a high level of mycorrhiza-mediated phosphorus uptake. The data suggest that host genetic factors influence fungal growth strategy with subsequent impact on plant biomass production.