Phenotypical and physiological study of near-isogenic durum wheat lines under contrasting water regimes

Irrigation treatments involving two water regimes were carried out in a controlled environment on eight near-isogenic durum wheat lines that differed in a major yield-related QTL region (QYld.idw-3B) in order to assess the relationship between morpho-physiological traits, antioxidant enzyme activities, and polyamine contents in the flag leaves, and drought tolerance. Drought stress, simulated under a rain-out shelter, negatively affected the performance of the isogenic lines, leading to significant reductions in seed yield, tiller number, chlorophyll content, plant height, leaf area, and ascorbate peroxidase activity, while the polyamine content and guaiacol peroxidase activity increased. The ascorbate peroxidase activity was negatively correlated with seed weight per main (r = − 0.446) and side spike (r = − 0.465) and the 1000-grain weight of the main and side spike (r = − 0.396 and r = − 0.49, respectively) and the guaiacol peroxidase activity with the number of seeds per main (r = − 0.457) and side spike (r = − 0.378) and the seed weight per side spike (r = − 0.38). PUT, SPD, and SPN contents showed a significant positive relationship with the number of seeds per main spike (0.534***, 0.496***, and 0.481**, respectively) and the seed weight per main spike (0.383*, 0.352*, and 0.399**, respectively). ANOVA showed that the QYld.idw-3B ++ lines had significantly better yield performance under non-watered conditions than the QYld.idw-3B −− lines, but their response to drought stress was not uniform regarding other yield-related traits.