Agronomic Performance and Flowering Behavior in Response to Photoperiod and Vernalization in Barley (Hordeum vulgare L.) Genotypes with Contrasting Drought Tolerance Behavior

Abstract In dry environments, the appropriate matching of reproductive development with water availability is considered very crucial for crop success. In this study, the role of variations in flowering time and drought tolerance in selected barley genotypes with contrasting drought tolerance behavior was studied under field and controlled conditions. For this purpose, field trials were conducted for two consecutive seasons at three diverse locations where the studied genotypes were subjected to either rainfed conditions or rainfed plus supplementary irrigation under two different sowing dates. Furthermore, reproductive meristem development was assessed in two selected barley genotypes, Rum (drought tolerant) and Steptoe (drought-sensitive), in response to both vernalization and water stress under two different photoperiod conditions. Variation in the number of days to heading was more pronounced under rainfed conditions than under well-water conditions. For agronomic performance, Rum was superior under all tested environments, which assures its general adaptability to dry environments. Under controlled conditions, the transition to reproductive meristem was faster under vernalized long-day conditions compared to vernalized short-day conditions. The progress of shoot apical meristem development and heading under long-day conditions was significantly faster in Rum compared to Steptoe. A pronounced effect of drought stress was observed on shoot apical meristem development in Steptoe. Under short-day conditions, vernalized Rum plants subjected to drought showed an advanced meristem development stage and a significantly earlier heading compared to non-stressed plants. This early heading in stressed Rum plants under short-day conditions was accompanied by higher gene expression of the Vrn-H1 and Vrn-H3 genes. In conclusion, the integration of vernalization and photoperiod signals in drought-tolerant barley genotypes was associated with early flowering time and higher productivity in dry environments.