Germination Dynamics and Speed Parameters of Rice under Iron Toxicity Stress

Abstract

Iron toxicity is a major abiotic stress limiting rice production in lowland ecosystems, negatively impacting crop establishment from the critical germination stage. This study investigated the impact of iron toxicity on germination dynamics and speed parameters across 12 diverse rice genotypes. Seeds were exposed to four iron concentration levels (0, 300, 450, and 600 mg/L Fe²⁺) in a controlled environment. Results showed a highly significant (p ≤ 0.01) main effect of genotype and Fe level, as well as an interaction between genotype and iron stress, for all parameters. Iron toxicity caused a dose-dependent reduction in germination, significantly lowering FGP, GE, GRI, and GI while increasing MGT in sensitive genotypes. However, substantial genotypic variation was observed. The genotypes FARO 26, FARO 52, and FARO 50 were identified as highly tolerant, maintaining superior germination performance, characterized by high FGP (>77%), rapid germination (high GRI and GE), and high overall GI, even at the highest iron concentration of 600 mg/L. Conversely, FARO 33, FARO 57, and FARO 17 were highly sensitive, showing drastic declines across all metrics. The findings indicate that germination speed and synchronization are critical early indicators of iron stress tolerance. The identified tolerant genotypes are recommended for direct use in iron-toxic regions and serve as valuable genetic resources for breeding programs targeted at improving seedling establishment and yield stability in stress-prone environments.