Identification of Water Use Strategies at Early Growth Stages in Durum Wheat from Shoot Phenotyping and Physiological Measurements.

Modern imaging technology provides new approaches to plant phenotyping for traits relevant to crop yield and resource efficiency. Our objective was to investigate water use strategies at early growth stages in durum wheat genetic resources using shoot imaging at the ScreenHouse phenotyping facility combined with physiological measurements. Twelve durum landraces from different pedoclimatic backgrounds were compared to three modern check cultivars in a greenhouse pot experiment under well-watered (75% plant available water, PAW) and drought (25% PAW) conditions. Transpiration rate was analyzed for the underlying main morphological (leaf area duration) and physiological (stomata conductance) factors. Combining both morphological and physiological regulation of transpiration, four distinct water use types were identified. Most landraces had high transpiration rates either due to extensive leaf area (area types) or both large leaf areas together with high stomata conductance (spender types). All modern cultivars were distinguished by high stomata conductance with comparatively compact canopies (conductance types). Only few landraces were water saver types with both small canopy and low stomata conductance. During early growth, genotypes with large leaf area had high dry-matter accumulation under both well-watered and drought conditions compared to genotypes with compact stature. However, high stomata conductance was the basis to achieve high dry matter per unit leaf area, indicating high assimilation capacity as a key for productivity in modern cultivars. We conclude that the identified water use strategies based on early growth shoot phenotyping combined with stomata conductance provide an appropriate framework for targeted selection of distinct pre-breeding material adapted to different types of water limited environments.

Shoot and root phenotyping of the barley mutant kcs6 (3-ketoacyl-CoA synthase6) depleted in epicuticular waxes under water limitation.

Aerial parts of plants are separated from the environment by a cuticle which functions in protection against desiccation and pathogen attack. Recently, we reported on a barley mutant with defect in the 3-KETOACYL-CoA-SYNTHASE (HvKCS6) gene, resulting in reduced coverage of the cuticle with epicuticular waxes. Spores of adapted and non-adapted powdery mildew fungi germinated less frequently on mutant leaves possibly because plant derived signals are missing. We used a shoot and root phenotyping facility to test whether depletion in epicuticular waxes negatively impacts plant performance under water-limiting conditions. While shoots of mutant plants grew slower at well-watered conditions than wild-type plants, they showed an equal or slightly better growth rate at water limitation. Also for roots, differences between mutant and parental line were less prominent at water-limiting as compared to well-watered conditions. Our results challenge the intuitive belief that reduced epicuticular wax might become a drawback at water limitation.