Recent Insights in Rice Blast Disease Resistance

Magnaporthe oryzae that causes blast disease in rice is one of the most notorious phytopathogenic fungi responsible for severe economic loss in rice production. The fungus is one among the top ten devastating biotic threats to food security worldwide. To counter the pathogen and minimize the losses, various biological, conventional, and advanced molecular approaches have been utilized. Conventional and marker-assisted selection (MAS) breeding methods were deployed and varieties having tolerance or resistance have been developed. Durable and broad-spectrum resistance is the demand of the hour to protect the crop against blast disease, and several studies have made significant progress in this direction. Identification and molecular characterization of different blast resistance genes (R) and defense regulators (DR), and their deployment in various cultivars, is the most preferred approach to breed the disease-resistant varieties. The inclusive approaches including quantitative trait locus (QTL), association mapping, allele mining, bioinformatics tools and genetic engineering, miRNA, genome editing, CRISPR/Cas9 etc. have contributed to the strengthening of molecular breeding and providing of new opportunities for the development of rice varieties resistant to blast. Recent advances show that R-genes Pikh, Pi-1, Pi9, Pi20, Pi27, Pi39, Pi40, and Pita impart broad-spectrum resistance against blast disease. The bsr-d1, bsr-k1, spl11, spl33, and OsBBI1 transcription factors have also been reported for broad-spectrum resistance. The R-genes are broadly classified into eight groups, and in plants, the NBS-LRR genes correspond to the major group. These R-genes are the master keys of the entire defense system of plants, act in multilayered surveillance, and are governed by various extra- and intracellular receptor molecules to ward off pathogen invasion. The updated information on rice blast pathogen provided here will help to understand the different mechanism, advancement in resistance gene research, and focus on the breeding program in rice against blast disease.