Genetic approaches to impart brown leaf spot resistance in rice: A review

Brown leaf spot (BLS) of rice, caused by the fungal pathogen Bipolaris oryzae, is a widespread and economically significant disease affecting rice-growing regions worldwide. Historically known for contributing to the Bengal famine during the 1940s, the disease continues to impact both yield and grain quality, especially in rice grown in rainfed and nutrient-deficient ecologies. Despite its long-standing presence, Brown leaf spot remains as an under-researched disease compared to other major rice pathogens, limiting progress in resistance breeding. Climate change and widespread drought events have witnessed an increased incidence of this disease in the recent past. Therefore, developing stable and broad-spectrum resistance to multiple strains of Bipolaris oryzae across diverse agro-ecological zones is essential. This review provides insight into recent advances that are transforming BLS resistance breeding from the discovery of novel resistance donors in diverse germplasm to the deployment of high-resolution Quantitative Trait Loci (QTL) mapping, genome-wide association studies (GWAS) and Clustered Regularly Interspaced Short Palindromic Repeats associated protein 9 (CRISPR-Cas9) based functional gene validation. It highlights how combining conventional breeding with molecular tools like marker-assisted selection and gene pyramiding accelerates the development of rice lines with broad and durable BLS resistance. The review emphasizes recent advances that support more efficient and climate-resilient breeding strategies for sustainable rice production.