Rapid upregulation of Dehyrin3 and Dehydrin4 in response to dehydration is a characteristic of drought tolerant genotypes in barley

The identification of molecular markers and marker-aided selection are essential to the efficient breeding of drought-tolerant plants. However, because that characteristic is controlled by many quantitative trait loci, such markers that can screen and trace desirable barley genotypes in a segregating population or germplasm have not yet been determined. Relative water content has been used to estimate drought tolerance in plants because it is highly correlated with the drought index of yield. To develop reliable gene-specific markers for identifying tolerant versus susceptible genotypes, we performed suppression subtractive hybridization to identify candidate genes. We used two domestic barley cultivars, one having the highest RWC (drought-tolerant 'Chalbori') and the other having the lowest (drought-susceptible 'Daebaekbori'). In response to dehydration at the early seedling stage, rapid upregulation of Dehydrin3 (Dhn3) and Dhn4 occurred in the drought-tolerant genotypes, but not in the susceptible ones. Similar results were obtained with mature plants growing under frequent drought stress in the greenhouse. In addition, Dhn3 and Dhn4 conferred higher drought tolerance when they were over-expressed in transgenic Arabidopsis. Thus, in addition to using assessments of RWC, we propose that Dhn3 and Dhn4 expressions can serve as drought-induced gene-specific markers to determine drought-tolerant barley genotypes at the seedling stage.