Abstract

                                Rice productivity faces significant challenges from climate change and sudden outbreaks of pests and diseases. Conventional breeding alone struggles to produce stress-resistant varieties, making marker-assisted breeding (MAB) a valuable complement. MAB enhances conventional breeding by employing molecular markers tightly linked to target genes, increasing efficiency without entirely replacing traditional methods. This review evaluates gene introgression effects and the role of MAB in improving rice productivity based on secondary data sources. Notable gene targets include Xa4, Xa5, Xa13, Xa21 and Xa27 for bacterial blight; Pi2, Pi5, Pi9 and QTLs on chromosomes 1, 2, 11 and 12 for blast resistance; Gm1 and Gm4 for gall midge; Saltol for salinity tolerance; qDTY1.1, qDTY2.1 and qDTY3.1 for drought tolerance; Sub1A for submergence; and yld1.1, yld2.1 and GW6 for yield enhancement. Introgressing these genes has led to the development of resilient rice lines capable of thriving under biotic and abiotic stresses, with notable increases in yield over susceptible recurrent parents. For instance, the introgression line DHA-10 (5.68 t/ha) yields more than its parent BPT5204 (4.97 t/ha), while the submergence-tolerant BR9157-12- 2-37-13-17 produces 3.44 t/ha, outperforming BRRI dhan33 (1.73 t/ha). These cases illustrate the transformative impact of MAB in developing highyielding, resilient rice varieties, underscoring its invaluable role in enhancing rice productivity under diverse stress conditions. Rice (Oryza sativa L.) is a primary staple crop, vital to the food security of over half the world’s population, particularly in Asia and Africa, where it is fundamental to dietary intake and economic stability (Suela et al., 2019). Globally, rice supplies nearly onefifth of caloric intake and contributes around 15% of dietary protein, underscoring its importance in global nutrition (FOA, 2004). Originating in Southeast Asia, rice cultivation has expanded worldwide, with China, India and Bangladesh currently leading in production, reporting outputs of 146.73, 118.00 and 35.85 million metric tons, respectively. These countries achieve average yields of 7.06, 4.02 and 4.55 metric tons per hectare from cultivation areas spanning 29.69, 44.00 and 11.83 million hectares, respectively (USDA, 2020). However, rice production’s challenges are intensifying with accelerated industrialization, urbanization and population growth. The availability of arable land is decreasing, resulting in agricultural areas being repurposed for non-agricultural use. This is particularly concerning as rice yield growth stagnates in regions like Bangladesh, where yields average only 4.5 t/ha (BRRI, 2018). Additionally, rice breeders face mounting pressures fof various biotic and abiotic stresses exacerbated by climatic variability.

Key words : Marker-assisted breeding (MAB), Rice (Oryza sativa L.), Stress tolerance, Gene introgression, Yield enhancement