Morpho-physiological Responses of Rice Genotypes to Iron Toxicity during Germination and Early Seedling Growth

Abstract

Iron toxicity is a major abiotic stress that significantly limits rice production in lowland ecosystems. The early germination stage is highly vulnerable to this stress, making it a critical phase for screening tolerant genotypes. This study aimed to identify iron-tolerant rice genotypes through morpho-physiological assessment during germination and early seedling growth. Twelve rice genotypes were evaluated under controlled iron stress conditions (0, 300, 450, and 600 mg/L Fe²⁺). The experimental design was a completely randomized design with four replications. Morpho-physiological parameters, including final germination percentage, plumule length, radicle length, and seedling vigour index, were measured following standard protocols. Data were analyzed using ANOVA, and mean separation was done with Tukey's HSD test at P ≤ 0.05. The results revealed significant (P < 0.01) genotypic variation in response to iron toxicity. Iron stress caused dose-dependent suppression of all growth parameters, with the most severe inhibition observed at 600 mg/L Fe. The genotypes FARO 52 and FARO 50 demonstrated exceptional tolerance, maintaining the highest values for final germination percentage (85 % and 83 %), plumule length (5.27 cm and 5.12 cm), radicle length (4.62 cm and 5.02 cm), and seedling vigour index (841.55 and 842.15) at the highest stress level. In contrast, FARO 33 showed extreme sensitivity with the lowest values across all parameters. FARO 26 displayed moderate tolerance, particularly in maintaining seedling vigour index under stress conditions. This study successfully identifies FARO 52 and FARO 50 as elite iron-tolerant rice genotypes based on their superior morpho-physiological performance during germination. These genotypes are recommended for direct cultivation in iron-toxic soils and as valuable donor parents in breeding programs aimed at enhancing iron tolerance in rice.