CaCl2 treatment improves drought stress tolerance in barley (Hordeum vulgare L.)

Spring drought can adversely affect the productivity of barley (Hordeum vulgare L.) by reducing the yield. Because seed osmopriming can enhance crop productivity, we examined the potential of CaCl2 treatment to improve drought tolerance in spring barley. Initially, we applied the priming procedure (5, 50, and 500 mM) to caryopses and assessed its effectiveness using a routine germination test, followed by measuring the level of divalent cations. Since drought adaptation is a complex phenomenon, we tested a comprehensive set of physiological parameters including (1) relative water content (RWC), (2) gas exchange parameters, and (3) photosynthetic pigments concentration in leaves of 3-week-old plants developed from the seeds subjected to osmopriming, followed by exposure to increasing water shortage. The plants were sampled at two selected time points, determined by soil moisture retention (pF = 3.6 and 4.2). The effect of CaCl2 pretreatment was characterized in three distinct spring barley varieties, which differed in their response to drought stress (drought-tolerant Sebastian and Cam/B1/C1 and drought-susceptible Georgie), to assess potential interactions between osmopriming and genetically determined drought tolerance. Our results clearly demonstrate that CaCl2 priming improves drought tolerance in stress-tolerant as well as drought-susceptible barley cultivars. Furthermore, we show that the beneficial effects of calcium preconditioning interact significantly with genetically determined drought tolerance.