Akram Oraki, Ehsan Shahbazi, Keramatollah Saeidi, Fariba Rafiei,
Volume 12, Issue 2 (3-2026)
Abstract
Objective: This study evaluated the effects of polyethylene glycol (PEG)-induced drought stress on germination traits, seedling growth, and seed vigor across 24 Nigella sativa genotypes to identify drought-tolerant and -sensitive genotypes.
Method: The experiment was a factorial arrangement based on a completely randomized design (CRD) with three replications, conducted at the Crop Physiology Laboratory of Shahrekord University. The factors comprised 24 N. sativa genotypes and five drought levels induced by PEG at osmotic potentials of 0 (distilled water, control), -0.2, -0.3, -0.4, and -0.6 MPa. Measured traits included germination percentage and rate, mean germination time, root and shoot length, seedling length, seedling fresh and dry weight, and seed vigor.
Results: Analysis of variance (ANOVA) revealed that genotype, drought, and their interaction significantly affected all germination and early seedling growth traits. The strongest positive correlations were observed between seed vigor and seedling length, seedling length and root length, and seed vigor and root length. Principal component analysis (PCA) of the nine traits identified three components with eigenvalues >1, accounting for 87.91% of the total variance. Based on the PCA biplot and Ward's hierarchical cluster analysis, the genotypes were classified into three groups: tolerant (genotypes 3, 8, 11, 24), semi-tolerant (genotypes 1, 2, 9, 12, 14, 17), and sensitive (the remaining 14). Multivariate tests (Pillai's trace, Wilks' lambda, Hotelling-Lawley trace, and Roy's largest root) confirmed highly significant differences among the three groups (p < 0.01), validating the classification robustness.
Conclusions: The findings reveal significant genetic diversity among N. sativa genotypes under drought stress. Genotypes 3, 8, 11, and 24, which showed superior germination performance, are recommended for future breeding programs. Furthermore, clustering enables the selection of parental lines with greater genetic distance (e.g., tolerant genotype 3 and sensitive genotype 5) for hybridization, facilitating the genetic analysis of drought tolerance mechanisms and supporting trait improvement efforts.
Highlights:
- Rapid, cost-effective PEG screening replaces field selection
- Root length as a reliable indicator of seed vigor
- Identifying 4 superior Nigella genotypes for drought tolerance
