Meeting Abstract
Arbuscular mycorrhizal fungi (AMF) are known to facilitate nutrient uptake and increase production of chemical defenses in plants, both which can improve plants’ ability to resist insect herbivory. Cover crops – non-commercial species planted in between cash crops in a crop rotation – can naturally alter both soil nutrients and AMF communities. We tested whether different cover crop species could alter AMF colonization, plant chemistry, and plant-insect interactions in a proceeding cash crop. Cover crop species were either non-mycorrhizal, non-leguminous (canola, forage radish), mycorrhizal non-leguminous (cereal rye, oats), mycorrhizal leguminous (clover, pea), or absent (fallow). We measured the cascading consequences of each treatment on AMF colonization, cash plant (field corn) performance and an herbivorous insect (European corn borer) feeding on the plants. Plant N was higher in corn proceeding leguminous cover crops (pea and clover) than non-leguminous cover crops. Corn root AMF colonization was greater in plots previously planted with mycorrhizal cover crops than non-mycorrhizal or no cover crops. AMF colonization was strongly linked to plant P, and plant N:P ratio was predictive of corn plant height. Insect survivorship significantly differed among cover crop treatments, being highest on corn planted after a radish cover crop. Preliminary quantitative real time PCR (qRT-PCR) showed that constitutive levels of maize protease inhibitor (MPI) transcript in corn plants were marginally correlated with plant phosphorus and with European corn borer survivorship. Our data show that cover crops have indirect consequences on corn pest performance, via the pathways of altering AMF colonization, nutrient uptake, and chemical defense production in the cash crop.
