Unraveling zinc acquisition strategies in barley: the role of phytosiderophore exudation and root-associated microbiome

A nutritious and healthy diet relies on consuming cereals with sufficient micronutrient content, making the production of nutrient-rich crops a crucial agricultural goal. Identifying key strategies for plant micronutrient acquisition is essential, and this is especially critical for regions where calcareous or nutrient-deficient soils limit micronutrient bioavailability.

Plants can enhance nutrient uptake by increasing exploration of the soil volume through root growth or by releasing root exudates that facilitate nutrient mining. Barley, along with other gramineous plants, employs an efficient strategy to mobilize micronutrients which is based on chelating agents called phytosiderophores (PS). While the role of these compounds in iron acquisition is well known, their function in zinc (Zn) nutrition is unclear. Furthermore, root-associated microorganisms are also known to interplay on the plant's micronutrient status either by enhancing the general plant health or directly making micronutrients bioavailable.

This study aimed to identify key root traits for an efficient Zn acquisition in barley. Sixteen barley genotypes with diverse genetic backgrounds were grown in a Zn-deficient soil. Total carbon and nitrogen exudation were measured, and PS quantification as well as characterization was performed. To investigate the root-associated microbiome, amplicon sequencing of the 16S rRNA gene and the ITS2 region was conducted. PS exudation showed a positive correlation with barley Zn shoot concentration highlighting its potential role in plant Zn nutrition. While root-associated microorganisms were influenced by the plant’s micronutrient status, we didn´t see clear evidence of their role in plant Zn nutrition. These findings provide valuable insights about plant-soil-microbe interaction for nutrient-efficient crop production.