Ozone-Tolerant Rice for Air-Polluted Environments

Recent decades have witnessed a surge in tropospheric ozone concentrations across many Asian countries, including Bangladesh, posing a significant threat to rice yields and regional food security. This study presents a comprehensive marker-assisted breeding program designed to introgress two quantitative trait loci (QTL) conferring ozone tolerance into elite Bangladeshi rice varieties. We crossed the donor landrace Kasalath with high-yielding varieties BRRI dhan28 and Binadhan-11, generating BC₂F₄ lines with an average of 87% recipient parent genome recovery. These lines harbored diverse combinations of positive alleles at the target QTLs while retaining the agronomic traits of modern rice varieties. In controlled open-top-chamber experiments, the presence of these QTLs in elite backgrounds mitigated ozone stress symptoms, reduced physiological damage such as lipid peroxidation or loss in photosynthetic CO₂ assimilation rates, and alleviated yield losses. Field trials conducted in a high ozone stress environment in Bangladesh, with and without the ozone protectant ethylenediurea (EDU), revealed that sensitive recipient parents suffered under ambient ozone concentrations. In contrast, the ozone-tolerant lines exhibited significantly less yield loss and were less affected by pollution. Our findings demonstrate the efficacy of marker-assisted breeding in adapting rice to changing atmospheric conditions, offering a robust strategy for safeguarding food security in the face of global change.