Automated Phenotyping Unveils Trait-Specific Genotypic Variation in Arbuscular Mycorrhiza Responsiveness in Maize...

Arbuscular mycorrhiza (AM), a symbiosis between land plants and fungi that enhances plant mineral nutrition, has potential for application in sustainable agriculture. The extent to which plants benefit from the symbiosis depends on the plant-fungal genotype combination, providing opportunities for breeding symbiosis-optimized crops. Here, we analyzed several plant growth traits and shoot mineral element accumulation of 15 genetically diverse maize inbred lines in response to AM. Plants were grown in an automated phenotyping system, in which randomization produced reproducible shoot surface growth curves. We observed strong variation in AM responsiveness of shoot and root growth in a phosphate-poor alkaline substrate. This substrate caused stunted growth in non-inoculated control plants and a 165% to 633% increase in plant biomass in AM plants. We observed variation among the maize lines in the AM-mediated increase in total shoot content of 24 mineral elements plus phosphate and sulphate. While nitrate accumulated in control plants, it was not detectable in the shoots of AM plants. Growth traits and accumulation of mineral elements were not uniformly correlated across the 15 maize lines. An exploratory ridge-regression analysis showed that R_AM was only selectively predictable across traits, indicating that R_AM is mostly trait-specific rather than uniformly coordinated across traits.