The genetic architecture of host response suggests a trade-off between mycorrhizal and non-mycorrhizal performance in field-grown maize

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in cultivated soils, forming symbiotic relationships with the roots of major crop species. Although physiological and molecular genetic studies have demonstrated the potential of the symbiosis to enhance host plant nutrition and alleviate environmental stress, experimental difficulties have complicated estimation of the actual benefit in the field. Furthermore, host response to the symbiosis can range from positive to negative depending on the plant variety. Here, a novel mapping strategy, based on the use of AMF-resistant plant varieties, was implemented to evaluate maize response to arbuscular mycorrhiza in the field. Arbuscular mycorrhiza were found to make a significant contribution to plant growth and yield components, both in terms of absolute affect and as a source of variation among plant genotypes. Characterization of the genetic architecture of host response distinguished mycorrhiza dependence and benefit, and indicated genetic trade-offs between mycorrhizal and non-mycorrhizal growth. This approach is applicable to other crop species, permits further mechanistic analysis and is scalable to yield trials.