Abstract:
Drought is a detrimental abiotic stress that severely limits wheat growth and productivity worldwide by altering several physiological processes. Thus, understanding the
mechanisms of drought tolerance is essential for the selection of drought-resilient features
and drought-tolerant cultivars for wheat breeding programs. This exploratory study evaluated 14 wheat genotypes (13 relatively tolerant, one susceptible) for drought endurance
based on flag leaf physiological and biochemical traits during the critical grain-filling stage
in the field conditions. Measurements included six physiological, seven gas exchange,
six photosystem II, six stomatal, three reactive species, seven metabolomic solutes, and
two biomass traits. All parameters were significantly influenced by drought, with varying genotypic responses. Hierarchical cluster analysis (HCA) categorized genotypes into
three drought tolerance groups based on trait performance. Seven genotypes in Cluster
2 (BARI Gom 26, BARI Gom 33, BD-631, BD-600, BD-9910, BD-9889, BD-637) exhibited
superior drought tolerance, characterized by minimal changes in physiological traits and
biomass accumulation, reduced oxidative stress markers, and increased accumulation of
osmoprotectants. The innovative multi-trait genotype-ideotype distance index (MGIDI)
further ranked wheat genotypes in regard to drought tolerance, identifying BARI Gom
33, BARI Gom 26, BD-9889, and BD-600 as top performers. Notably, all these top-ranking
genotypes belonged to Cluster 2, previously identified as the highest-performing group in
the HCA. The identified genotypes with superior drought tolerance offer valuable genetic
resources for enhancing wheat productivity in water-limiting environments. Traits related
to photosynthetic activity, biomass gain, leaf conductance, water stress, and osmoprotection
showed high selection differentials and heritability in MGIDI analysis, indicating their
potential as selection targets for drought-tolerant wheat. Overall, the strategic approaches
have yielded novel insights into genotype screening that can be directly applied to deepen
our understanding of drought tolerance mechanisms in wheat.
