Effects of different mycorrhizal associations on performance within a plant-hybrid complex

Root-dwelling endotrophic fungi (AMF) are found as obligate symbionts in most plant families and in an estimated 80% of all terrestrial plant species.  We investigated the prevalence and effects of mycorrhizal symbioses within the Piriqueta caroliniana complex, a group of morphologically-variable, seasonally drought-stressed, subtropical herbaceous perennial plants.   We asked specifically whether susceptibility to AMF infection varied among genotypes, which are adapted to different moisture regimes and edaphic conditions, and across different sources of soil inoculum.  To address these questions, we used a series of greenhouse experiments in which different genotypes from the Piriqueta hybrid complex were exposed to various soil inoculae.  Vegetative cuttings from different genotypes were grown in sterile sand medium amended with inocula obtained from soil collected in sites occupied by two different morphotypes (north and south Florida), or a commercially available mycorrhizal mix soil amendment.  After 8 weeks, plants were harvested, intraradical AMF were quantified via visualization techniques, and data were analyzed with SAS.   The three inoculum types varied in their infectiousness; more intraradical hyphae (P = 0.0012) and arbuscules (P = 0.0417) formed in roots grown with native rather than commercial soil inoculum.  In another experiment, using a single AMF inoculum source, we found that up to 59% of variation in shoot biomass accumulated under water stressed conditions was associated with AMF infection (P = 0.0021). These findings suggest that plant-AMF interactions within the Piriqueta complex are strongly influenced by both host genetics and environmental edaphic conditions.