Effects of drought on morpho-physiological attributes and secondary metabolites of wheat genotypes: Growth traits, seed yield and stress tolerance indices.

• Drought caused wheat genotype specific decreasing trend in various agronomic traits. • Genotype-specific variations were observed in defense system under drought stress. • Better stress tolerance indices were found in BS3, BS4, BS8, BS9 and BS20 genotypes. • Both physio-biochemical and agronomic traits can be considered in breeding programs. In parallel with rapid growth in human population, increasing deficiency of water for irrigation along with abruptly changing environmental conditions has increased the food insecurity problem which needs immediate attention to secure the future food security. This study aimed to identify the water stress tolerance and high yielding potential of newly developed wheat genotypes, based on agronomic, morphological and biochemical aspects, along with the stress tolerance indices (STI). These genotypes were developed through conventional breeding from a cross (Bhakkar x S-24) and named as BS following the names of the parental genotypes. The experiment comprised a total 20 newly developed genotypes and 2 parental genotypes. Split plot field experiment was conducted using reduced number of irrigations as water stress treatment. All studied genotypes exhibited distinct negative impacts of deficit irrigation with respect to various studied agronomic attributes but was genotype specific. There were genotype-specific variations to deficit irrigation, regarding leaf chlorophyll contents, water relations, membrane lipid peroxidation, as well as antioxidative defense mechanism. Under deficit irrigation genotypes BS3, BS4, BS8, BS9, and BS20 demonstrated superiority in growth and grain yield related attributes that was attributed to their effective performance in maintaining better water content through better osmotic adjustment, chlorophyll levels, as well as better defense against oxidative stress. Comparatively less reductions in growth and yield i.e 26.43 % and 30.56 %, 28.94 % and 28.01 %, 32.13 % and 30.07 %, 34.35 % and 31.36 %, and 24.14 % and 26.55 % were recorded in BS3, BS4, BS8, BS9, and BS20 respectively as compared with remaining genotypes. However, the opposite was true for genotypes BS7, BS13, BS15 followed by BS6 and BS7. Stress tolerance indices also showed the better tolerance of the genotype BS3, BS4, BS8, BS9 and BS20. In conclusion, breeding programs for the development of stress-tolerant wheat genotypes should also consider the physio-biochemical mechanisms alongside the agronomic traits. This holistic approach will contribute significantly for the selection of genotypes that exhibit resilience to water deficit stress with high yield potential. [ABSTRACT FROM AUTHOR]