The Genetic Control of Stomatal Development in Barley: New Solutions for Enhanced Water-Use Efficiency in Drought-Prone Environments

Abstract

Increased drought frequency due to climate change is limiting the agronomic performance of cereal crops globally, where cultivars often experience negative impacts on yield. Stomata are the living interface responsible for >90% of plant water loss through transpiration. Thus, stomata are a prospective target for improving drought tolerance by enhancing water-use efficiency (WUE) in economically important cereals. Reducing stomatal density through molecular approaches has been shown to improve WUE in many plant species, including the commercial cereals barley, rice, wheat and maize. Rice with reduced stomatal density exhibit yields 27% higher than controls under drought conditions, reflecting the amenability of grasses to stomatal density modification. This review presents a comprehensive overview of stomatal development, with a specific emphasis on the genetic improvement of WUE in the grass lineage. Improved understanding of the genetic regulation of stomatal development in the grasses, provides significant promise to improve cereal adaptivity in drought-prone environments whilst maximising yield potential. Rapid advances in gene-editing and ‘omics’ technologies may allow for accelerated adaption of future commercial varieties to water restriction. This may be achieved through a combination of genomic sequencing data and CRISPR-Cas9-directed genetic modification approaches.