Morphological, Physiological, and Metabolic Responses of Diverse Barley Inbreds to Dry Down and Moderate Drought Stress

Abstract

Drought stress alters the plant metabolism, physiology, and growth, and such responses might differ with the intensity of stress. We evaluated the genotypic diversity in plant morphology, photosynthetic responses, metabolite shift, and their relationship in 23 genetically diverse barley inbreds under control, dry down (DD), and moderate drought (MD) stress. DD triggered strong inhibition of photosynthetic health, while reducing plant size was the key strategy under MD stress. We observed that the induced changes under both stress scenarios occurred in a genotype-dependent manner. Compared to control conditions, the metabolism of simple sugars and polyhydroxy acids increased in MD and DD, while the maximum accumulation of amino acids, lipids, and phosphates occurred in DD stress. Accumulation of sugars and metabolites with unknown classification was the metabolic signature of drought-tolerant inbreds. Nevertheless, accumulation of a large pool of metabolites, including lipids, polyhydroxy acids, and amino acids in an inbred did not have a positive effect on drought tolerance and might be metabolically costly. The inbred plants’ tolerance to MD and DD originated from the semi-arid or sub-tropical regions, while drought-sensitive inbreds primarily came from temperate regions. Low stomata density, reduced water loss, and retarded growth under drought stress were the key features of inbreds with better survival capacity under severe dehydration. We identified drought-tolerant barley inbreds, and our study offers resources for future genetic research on various drought tolerance strategies.