Understanding a link between phosphorus deficiency and root carboxylate-driven silicon mobilisation for sustained yield in cultivated and wild barley

Background and aims: Phosphorus (P) deficiency limits cereal productivity worldwide, yet the traits that confirm plant ability to adapt to low-P conditions remain elusive. This work compared cultivated and wild barley – two species with contrasting responses to P availability—to investigate possible links between root carboxylates exudation, seed elemental composition (with a focus on silicon), and crop yield under P limitation. Methods: Ninety-six barley genotypes (63 cultivated Hordeum vulgare and 33 wild H. spontaneum) were grown under two soil P levels: low (P5) and moderate (P20). Agronomic traits were quantified and analysed by two-way mixed-effects ANOVA with P level, species, and their interaction as fixed factors. Root carboxylate exudation was measured, seed Si and Zn concentrations were determined, and correlation analyses were used to link exudation and seed elements with yield. Yield stability was assessed across genotypes. Results: Substantial genetic variation was observed. Wild barley showed greater yield stability and a narrower performance range under P5 than cultivated barley. P level, species, and their interaction significantly affected most traits, with the strongest P × species interaction for root dry weight and harvest index. Root carboxylate exudation correlated positively with seed Si and Zn, particularly in wild barley. Seed Si concentration positively related to grain yield under P5, but not under P20. Conclusions: Under low P, yield variation across barley genotypes was linked to root carboxylate exudation and seed silicon concentration. These findings offer new candidate traits to be targeted in breeding programs for developing barley varieties better adapted to P-deficient soils.