Natural variation of AM responsiveness in maize

Left: Field trial with European inbred maize lines in the rain out shelter to simulate drought (Foto: Peter Muth). Right: Drought stressed maize plants in the greenhouse non-inoculated (control) and inoculated (AM) with an arbuscular mycorrhiza fungus (Foto: Florian Berger).

Depletion of mineral nutrient resources, such as phosphate, decreasing soil fertility in several parts of the world, and environmental change leading to adverse climatic conditions, such as drought, threaten agricultural productivity. Therefore, strategies for sustainable crop production and soil management are needed to feed the human population.

Arbuscular mycorrhiza (AM) symbiosis enhances plant nutrition with vital mineral nutrients because the AM fungi explore a larger soil volume than the root with their extraradical hyphal network and moreover stimulate root development (Gutjahr and Paszkowski, 2013). In addition, AM symbiosis enhances the resistance of plants to biotic and abiotic stresses, such as certain pathogens, drought, salinity and heavy metal toxicity. Application of AM fungi has therefore the potential to make an important contribution to sustainable agriculture in low fertility soils or stressful environments with reduced pesticide and chemical fertilizer input (Sawers et al., 2008; Gianinazzi et al., 2010).

However, the magnitude of the AM-impact on plant performance depends on the combination of plant species/accession and the fungal species (Hong et al., 2012; Sawers et al., 2017), a phenomenon called functional compatibility. If the AM symbiosis is to be applied in sustainable agriculture, it will be important to optimize plant-fungal genotype combinations for maximum benefit. We have therefore initiated research with the future aim to understand the molecular basis of functional compatibility. This may enable us to define tools for breeding arbuscular mycorrhiza-optimized crops, which efficiently profit from the symbiosis.

We currently focus on AM-mediated drought stress resistance and investigate in how far this varies among European maize inbred lines. To this end we are phenotyping a range of maize inbred lines in the greenhouse and in the field for the influence of AM on growth performance, yield and drought stress symptoms to answer the following questions:

How much variation in AM-mediated drought stress resistance can be found in European inbred maize lines?
Which lines show an optimal AM-response?
Can we use this material to identify genomic regions (and even alleles), which determine the amplitude of the AM-response under drought?

References

Gianinazzi, S., Gollotte, A., Binet, M.-N., Tuinen, D., Redecker, D., and Wipf, D. (2010). Agroecology: the key role of arbuscular mycorrhizas in ecosystem services. Mycorrhiza 20, 519-530.

Gutjahr, C., and Paszkowski, U. (2013). Multiple control levels of root system remodeling in arbuscular mycorrhizal symbiosis. Front Plant Sci 4, 10.3389/fpls.2013.00204.

Hong, J., Park, Y.-S., Bravo, A., Bhattarai, K., Daniels, D., and Harrison, M. (2012). Diversity of morphology and function in arbuscular mycorrhizal symbioses in Brachypodium distachyon. Planta 236, 851-865.

Sawers, R.J.H., Gutjahr, C., and Paszkowski, U. (2008). Cereal mycorrhiza: an ancient symbiosis in modern agriculture. Trends Plant Sci 13, 93-97.

Sawers, R.J.H., Svane, S.F., Quan, C., Grønlund, M., Wozniak, B., Gebreselassie, M.-N., González-Muñoz, E., Chávez Montes, R.A., Baxter, I., Goudet, J., Jakobsen, I., and Paszkowski, U. (2017). Phosphorus acquisition efficiency in arbuscular mycorrhizal maize is correlated with the abundance of root-external hyphae and the accumulation of transcripts encoding PHT1 phosphate transporters. New Phytol 214, 632-643.