Evaluation of physiological markers for assessing drought tolerance and yield potential in bread wheat

Carbon isotope discrimination (Delta) has been recognized as a valuable phenotyping tool in wheat breeding. However, technical expertise and analysis cost restrict its large-scale use. We examined the associations of ash content (AC), minerals content (Ca, K, Mg, Fe and Mn) and leaf chlorophyll content (Chl) with grain Delta and grain yield (GY) to assess their potential as substitute to grain Delta. We evaluated 49 wheat genotypes under two water deficit regimes (W-120 and W-200) in a rain-out shelter. Leaf chlorophyll content (Chl) was strongly correlated with grain Delta and GY under moderate water deficit regime (W-200). Significant and negative correlations (P < 0.01) of AC and potassium concentration (K) with grain Delta, and between AC and GY was observed under both water regimes, while manganese concentration (Mn) was negatively correlated with grain Delta under W-120 regime only and magnesium concentration (Mg) correlated negatively under the W-200 regime only. Grain Delta was correlated (P < 0.01) positively with photosynthesis rate (A), stomatal conductance (g(s)) and GY, while correlated negatively (P < 0.01) with intrinsic water use efficiency (iWUE) under both water regimes. Results confirm the role of grain Delta as an indirect selection criterion for drought tolerance under a wide range of drought conditions. Additionally, Chl is the most suitable trait to predict yield under moderate water deficit conditions. AC and K concentration in grain proved potentially useful and economical alternative criterion to grain Delta in the evaluation of differences in yield potential and drought tolerance in wheat under drought.