Physiological and genetic factors conferring silicon-mediated drought stress tolerance in barley

Abstract

This thesis investigates the physiological and genetic factors underlying silicon (Si)-mediated drought tolerance in barley (Hordeum vulgare L.). Using genotypic comparisons, genome-wide association studies (GWAS), and CRISPR-Cas9 mutants of Si transporters (HvLsi1 and HvLsi2), this work demonstrates that Si significantly enhances drought resilience in a genotype-dependent manner. In responsive cultivars, Si supplementation improves shoot biomass and water status by modulating stress hormones (ABA, JA) and metabolites (proline, GABA). Transcriptomic analysis reveals Si-driven modulation of redox homeostasis and photosynthetic efficiency genes. Crucially, experiments with lsi mutants confirm that endogenous shoot Si accumulation, rather than soil-mediated effects, is indispensable for these benefits. Additionally, natural variation in grain Si was found to support early seedling establishment. These findings identify key genetic pathways for developing drought-resilient barley.