Blast disease, caused by the fungal pathogen Magnaporthe grisea (Herbert) Borr. (anamorph Pyricularia oryza Cav.), is one of the most devastating diseases of rice, reducing yield up to 10 billion kilograms annually worldwide (Zeigler et al. 1994). Since the early 1950s agricultural chemicals have beensynthesized for blast disease control; however, excessive applications of agrochemicals can pose a threat to human health and the environment. The use of resistant cultivars with major resistance (R) genes still remains one of the most reliable methods to manage the diseases. Identification and incorporation of different blast resistance genes with overlapping resistance spectra have long been the main objectives of rice breeding programmes worldwide.