Exploring drought tolerance for germination traits of diverse wheat genotypes at seedling stage: a multivariate analysis approach

Wheat holds crucial global importance as a staple food in many regions. Drought stress significantly impedes seed germination of wheat. The lack of drought-tolerant wheat varieties hampers wheat production, especially in arid regions of the world. This study investigated seed germination and seedling growth in eighty wheat genotypes under moisture stress stimulated by polyethylene glycol (PEG⁶⁰⁰⁰). The study included two osmotic potentials induced by PEG-20% (ψ: -0.491 MPa) and PEG-25% (ψ: -0.735 MPa), as well as a control set without PEG. The data showed that dehydration caused by polyethylene glycol generally had an adverse effect on the morphological characteristics of wheat seedlings by causing substantial losses during the early germination stage. The results acquired from analysis of variance explained highly significant variances (p < 0.01) across genotypes (G), PEG-Treatments (T^PEG), and interactions between genotypes and PEG-Treatments (G x T^PEG) for all observed variables. Moisture deficit radically affected all studied seedling traits of bread wheat under rising osmotic stress, with germination percentage (GP), shoot length (SL), root length (RL), coleoptile length (CL), seedling length (SDL), root fresh weight (FRW), root dry weight (DRW), shoot fresh weight (FSW), shoot dry weight (DSW), seedling biomass (SBM) and seedling vigor index (SVI) reduced by about 30-95% compared to control (PEG-0%) to the maximum induced osmotic stress at -0.735 MPa. The coefficient of relative inhibition (CRI) rose in response to osmotic stress, demonstrating growth inhibition. Boxplots demonstrated a considerable decline under stress, although scatter plots and correlation matrices revealed significant positive associations for most seedling traits, except CRI. The histograms for most variables showed a wider value range and more diversified distribution patterns. Principal component analysis (PCA) and genotype by trait biplot emphasized that PC1 represented 94.29% of the cumulative variation, with an eigenvalue of 11.31 out of 12 components. The heatmap displayed diverse genotype and trait characteristics, indicating higher values for drought resistance and lower values for susceptibility in genotype performance. As indicated by a range of multivariate analyses, the wheat lines NR-499, NARC-2009 and Pakistan-2013 stood out as the most drought-tolerant among the genotypes; whereas Borlaug-2016, NR-514 and NR-516 were found to be highly susceptible, whereas SBM, SDL, SVI and CRI have been found key indicators for subsequent screening. These tolerant wheat lines offer promising potential for developing drought-tolerant varieties that could thrive in arid regions, thereby strengthening wheat production in water-stressed environments. Integrating these findings into breeding programs is crucial for realizing the potential of drought-tolerant wheat varieties in transforming global wheat production.