Assessing Greek Bread Wheat Landraces for their Drought Resistance Strategies

Abstract

The physiological mechanisms activated by 10 bread wheat (Triticum aestivum L.) landraces of Greek origin when facing drought were examined under field conditions during two cultivation seasons in Greece. Ten landraces of bread wheat were cultivated under four different degrees of water stress, induced by means of increasing distances from a drip irrigation line under rainout shelters. A number of morphological and physiological traits associated with water absorption (root surface density, water potential decline between the wettest and driest treatments, and osmotic adjustment) and water loss (stomatal sensitivity and leaf senescence) were monitored on seasonal and diurnal basis. Considerable differences among the landraces were detected for most of the examined traits (root surface density, degree of osmotic adjustment, stomatal sensitivity, and drought‐dependent leaf senescence). A discriminant function analysis using the examined traits revealed landraces and groups of them endowed with different potentialities for absorbing and consuming water. On this account, the landraces were assessed for their abilities to absorb and save water. The sensitivity of the stomatal mechanism, estimated from diurnal fluctuations of stomatal diffusive resistance, was the trait mainly responsible for a clear discrimination of all landraces. Osmotic adjustment was not found to be a mechanism of major importance in the behavior of the majority of the examined landraces under water stress conditions. The conclusions drawn from this kind of physiological approach are discussed in respect to the grain yield sensitivity of the examined germplasm to water shortage. Thus, landraces exhibiting higher potentials for water absorption and water consumption also exhibited higher yield stability under water stress.