Genotypic Variation in Rice Tolerance to Fe Toxicity During Germination and Establishment

ABSTRACT Background Poor crop establishment caused by Fe toxicity hinders the adoption of direct‐seeded rice cultivation in Fe‐rich soil. To date, there have been few reports on the genotypic variation in rice's Fe tolerance during the pre‐establishment period (i.e., germination and emergence). Aims The objectives of this study were to elucidate the germination and seedling vigor of diverse cultivars under various Fe levels, and to identify rice genotypes that can tolerate Fe stress during the pre‐establishment period. Methods We evaluated 19 genotypes, including japonica , indica , and aus accessions, in hydroponic culture, under Fe stress imposed from 0 to 30 days after sowing. Results High Fe (500 mg Fe 2+ L −1 ) did not affect germination in any genotype. However, 50 mg Fe 2+ L −1 retarded and reduced both shoot and root growth, 200 mg Fe 2+ L −1 caused partial mortality, and 400 mg Fe 2+ L −1 was fatal to plants after germination. We found significant genotypic variation in shoot growth under Fe stress. Two indica genotypes, “Pokkali” and “Cilamaya Muncul,” had the highest tolerance to high Fe, attributable to limited Fe accumulation in shoots, mainly due to high root Fe retention. “Pokkali” also had high Fe content per unit root weight in the Fe plaque under moderate Fe stress, suggesting the potential contribution of vigorous formation of a root Fe plaque to rice's Fe tolerance. Conclusions The study identified promising Fe‐tolerant donor genotypes for future rice breeding. We suggest that limiting Fe accumulation in shoots is important under high Fe stress during establishment.