QTL mapping and candidate gene sequencing for disease resistance in rice - Review

Rice serves as the major staple food for more than half of the world’s population and is being cultivated across the globe. However, huge production losses in rice crop occurs due to the biotic stresses such as fungal blast caused by Magnaporthe grisea. Rice blast is endemic to most of the rice-growing areas. Loss due to rice blast may range up to 90% depending upon the part of plant infected and severity of the disease. Development of resistant varieties against the pathogen is the most economical and coherent approaches to cope up with the disease and increase the production of rice crop. Identification of QTLs for disease resistance is the important step for the development of resistant cultivars. To identify the resistance QTLs, a candidate gene strategy has been established. This strategy is very effective for identification of the disease resistance QTLs in rice and other cereals. After identification, a single minor QTL can be utilized in rice improvement programmes by modulating the expression of the gene underlying the QTL. Pyramiding of two to three minor QTLs, whose expression can be managed and that function in several defence signal transduction pathways, is beneficial for breeding of rice cultivars that are resistant to major diseases. Thus, identification and subsequent utilization of QTLs can serve as economically importance approach in crop improvement programmes for imparting resistance towards the diseases.