Breeding approaches for bacterial leaf blight resistance in rice (Oryza sativa L.), current status and future directions

Bacterial leaf blight (BLB) is one of the most serious threats to the rice crop in irrigated and rainfed areas of the world. It is caused by Xanthomonas oryzae pv. oryzae and has been known for more than a century. Through rigorous screening and selection, a number of resistant cultivars have been produced and utilized, but resistance was overcome by the development of mutant strains of pathogen and by the dynamic change in Xoo populations. About 38 resistance genes have been reported in rice against the disease and a few have been cloned. The pyramiding of several resistance genes through marker assisted selection has been a quite effective strategy for combating the disease. However, new powerful tools such as transgenics have been introduced to make a significant impact. The purpose of this mini-review is to consolidate the existing knowledge about bacterial leaf blight in rice and the progress made both in conventional as well as in molecular dimensions of breeding together with potential findings and constraints.