Morphological Traits Associated with Drought Stress Tolerance in Six Moroccan Durum Wheat Varieties Released Between 1984 and 2007

Drought is one of the main environmental factors affecting grain yield and plant architecture in durum wheat. The present work was conducted to evaluate the contribution of morphological traits above flag leaf node on grain yield of six Moroccan durum wheat varieties released between 1984 and 2007 and grown under two water regimes (irrigated and rainfed) during the 2015–2016 crop season. The following morphological traits were measured at anthesis: Flag leaf length (FLL), flag leaf area (FLA), peduncle length (PL), spike length (SL), spike area (SA), and green leaf area (GLA). Days from sowing to anthesis (DSA) and grain-filling period (GFP) were recorded. In addition, grain yield per plant (GYP) was evaluated at maturity. Analysis of variance showed the greater effect of water stress in explaining total variability of the studied traits. Mean comparisons indicated that water deficit significantly affected GYP and all morphological traits; it shortened DSA and GFP by 4 and 7 days, respectively. Moreover, GYP, DSA, and GFP increased in modern varieties. In contrast, FLL, FLA, and PL were reduced from old to modern varieties. Under irrigated conditions, correlation studies revealed that GYP was positively associated to GLA. Regarding the rainfed trial, GYP was positively correlated to FLL. Additionally, negative relationships were found between GYP and DSA in both water regimes. Stepwise regression highlighted the relative importance of each morphological traits on the stress susceptibility index, FLL was the most consistent trait entered the model followed by PL and FLA. In this study, some morphological traits above flag leaf node proved to be useful tools to select for grain yield in water-limited environments.