Leaf Water Potential, Relative Water Content, and Diffusive Resistance as Screening Techniques for Drought Resistance in Barley

Rapid drought resistance screening techniques could accelerate selection of improved cultivars for semiarid areas. This study was conducted to determine if total leaf water potential, leaf relative water content, and leaf diffusive resistance could be used to differentiate between barley (Hordeum vulgare L.) cultivars differing in apparent drought resistance. Resistant and susceptible cultivars were selected by regressing individual cultivar yields against site mean yield for numerous yield trials. Individual plants were grown in cone-tainers (plastic tubes 25 mm in diameter and 123 mm long). The lower 30 mm of the cone-tainers were imbedded in sand so that roots emerging from the bottom of the cone-tainers were in the capillary fringe above a water table in the sand. Fifty plants were grown at a time in a sand bed, five replications each of five resistant and five susceptible barley cultivars of either two- or six-row head types. At the three-leaf growth stage total leaf water potential (Ψ,) was measured on the third leaf of each plant under low stress conditions (predawn). Water was then drained from the sand bed to stress the plants. Leaf diffusive resistance (LDR) was measured at 1000 and 1300 h each day as stress developed. When the PM diffusive resistance reached about 1000 s m⁻¹, relative water content (RWC) of the second leaf was determined. All measurements were repeated in three different trials for each head type. Relative water content and Ψ, differentiated between drought-resistant and drought-susceptible groups of twoand six-rowed barley at the 0.01 probability level in every trial. Leaf diffusive resistance differentiated between resistant and susceptible groups at the 0.01 or 0.05 level under low and high stress conditions. Neither RWC nor LDR allowed separation of cultivars within resistant or susceptible groups, but Ψ, did show differences between cultivars within groups. These techniques provide an easy method to screen for drought-resistant barley. Contribution no. 5-2016 from the Montana Agric. Exp. Stn.