Blast Disease of Rice: Evolution and Adaptation in Context of Changing Climate

Rice blast disease is known as rice rotten neck, rice blight of seedlings, ryegrass blast and Johnson spot in different locations and is considered as the most destructive disease of rice in the world. It is caused by a filamentous, ascomycetous fungus Magnaporthe oryzae (syn. Pyricularia oryzae), which is polycyclic in nature and spreads by asexual spores (conidia). The infection spreads inside the host cell without causing visible symptoms in the early stage and above ground tissues of rice plants. The disease is reported in almost all the rice-growing seasons and an estimated yield loss is 10–30% of the total production. It has the ability to infect more than 50 species of grasses, including economically important crops like rice, wheat, barley and pearl millet. This disease is effectively managed by avoiding excessive nitrogen application which enhances the leaf area in per unit area which induces disease susceptibility. Moreover, balancing of the use and application of nitrogen in three split doses (50% N at basal, 25% N at tillering stage and 25% doses of N at panicle initiation stage) minimises the threat of blast diseases in standing crops. Foliar spray of systemic fungicide like tebuconazole 75 WG @ 500–750 g/ha, tricyclazole 75 WP @ 500 g/ha, metominostrobin 20 SC @ 500 mL/ha, or azoxystrobin 25 SC @ 500 mL/ha was highly effective with its protectivity and curative efficacy against the diseases when applied at boot growth and heading stage. This book chapter emphasises on blast pathogen, evolution, adaptation, pathogenesis and management of rice blast in the context of changing climate.