Blast Disease in Rice: A Review

Rice blast caused by the fungal pathogen, Magnaporthe grisea (anamorph: Pyricularia grisea) limits rice yield in all major rice-growing regions of the world and the rice blast fungus, Magnaporthe oryzae, is responsible for the most serious disease of rice and is a continuing threat to ensuring global food security. The fungus has also, however, emerged as a model experimental organism for understanding plant infection processes by pathogenic fungi. This hemibiotrophic pathogen penetrates in epidermal cells and causes lesions on leaves, leaf collar, culm, culm nodes and panicle neck causing failure of seed filling. After successful penetration, the invasive hyphae grow rapidly in the host cells and caused blast lesions. in 5 to 7 days, the pathogen produces numerous conidia from the lesions and initiates a new infection cycle. A number of signal transduction pathways are implicated in appressorium-mediated plant infection and have been characterised as a potential means of developing new chemical intervention strategies for disease control. With the advent of new technologies like marker-assisted selection, molecular mapping, map-based cloning, marker-assisted backcrossing and allele mining, breeders have identified more than 100 Pi loci and 350 QTL in rice genome responsible for blast disease.