GABA-mediated modulation of drought stress tolerance and seed morphology during flax (Linum usitatissimum L.) germination via image analysis.

Seed coat color, a trait exhibiting significant phenotypic variation, has been reported in previous studies to influence key germination parameters, including germination percentage, germination rate, and mean germination time. Looking into these relationships can help us identify plant varieties that better withstand both living threats and environmental challenges, which would make breeding programs more effective and focused. The objectives of this study were to evaluate the drought tolerance of 20 flax varieties at the germination stage, investigate the effects of gamma-aminobutyric acid (GABA) on seed germination performance under drought stress conditions, and explore potential associations between seed coat color and germination parameters under both stressed and non-stressed conditions using digital image processing. The final germination percentage, germination speed, and span of germination were assessed for seeds germinated under various germination conditions, including 23% PEG (- 0.169 MPa), 10 mM GABA, 23% PEG + 10 mM GABA, and a control treatment at 25 ± 0.5 °C. The results demonstrated substantial genetic variation across all germination parameters measured in the seeds of 20 distinct flax varieties. Genotype-specific responses to drought stress were observed, with 10 mM GABA alleviating the effects of drought. Among the varieties tested, Hermes exhibited the highest drought tolerance, while Lisette and Bonny-Doon were identified as drought-sensitive. Digital image processing analysis revealed significant differences (p < 0.05) in drought tolerance levels among flax varieties based on variations in RGB values of their seed coats. Although no statistically significant correlations were found in direct pairwise correlations between the color parameters converted from RGB (Red, Green, and Blue) to L*a*b* and germination parameters, multivariate PCA-biplot analysis indicated that L* and b* values had a positive influence on germination performance. In contrast, seeds with higher a* values exhibited reduced germination performance. Furthermore, the biplot analysis suggested that varieties with lighter seed coats tended to show better germination compared to those with darker seed coats. These findings highlight the potential of incorporating seed coat color parameters into flax breeding programs, suggesting their role in enhancing seed germination and overall seed quality under various stress conditions.