Plants are frequently exposed to many biotic and abiotic factors that are detrimental to their growth and performance, such as drought and herbivory. However, many plants also form associations with belowground organisms like arbuscular mycorrhizal fungi (AMF) which can protect plants from such stresses. We investigated the effects of AMF associations on growth of two varieties of Panicum virgatum, switchgrass, under drought and plant parasitic nematode (PPN) stresses. We conducted a three-factor growth chamber experiment manipulating drought (absence/presence), AMF (+/- Claroideoglomus etunicatum), and plant variety (Cave-in-Rock or Alamo), and assessed responses of plant biomass, root architectural traits and root herbivory by Pratylenchus penetrans, a common PPN species. The eight treatment combinations were replicated ten times for the total of 80 pots.
Results/Conclusions
The two plant varieties differed in aboveground biomass at the end of the experiment, with Alamo being bigger than Cave-In-Rock. Across both varieties, AMF suppressed PPN populations, as plants grown in the absence of AMF had 70% more PPN than those grown in the presence of AMF. AMF also had significant interactive effects with drought on the root biomass of both varieties, with AMF plants having more roots than non-AMF plants in drought conditions but not in control conditions. AMF had interactive effects with plant identity on root length, where AMF reduced root growth in Cave-in-Rock but not in Alamo. Root to shoot ratios of Alamo plants were about 19% greater than that of Cave-In-Rock indicating a higher allocation of resources to shoots in Cave-In-Rock plants. The results from this experiment indicate that AMF provide some protection to plants against belowground herbivory and may differentially provide belowground benefits to the plant varieties. Switchgrass is a leading candidate bioenergy crop and results from this work suggest that AMF may provide real benefits to this crop when grown in marginal lands.