Rice blast and control methods

Rice infections caused by Magnaporthe grisea are a major disease that wreaks havoc in almost all ricegrowing countries. The economic importance of rice is huge, for more than half of the world's population, rice serves as the main source of calories. During epiphytotic years, blast can have a devastating effect on world rice production. Nowadays, this pathogen has evolved into an innovative model system for investigating host-pathogen interactions. The outbreak of the disease depends on the climatic conditions of different regions. The occurrence of the disease and symptoms vary from country to country. Susceptible varieties suffer huge losses in the rice crop. The main reason for the violation of rice resistance to blast is the high ability of the pathogen to variability. Virulent pathotypes cause severe morbidity. When examining the pathogenicity of the pathogen, pathotypes can be determined using a collection of different varieties of rice, which usually differ from each other, carrying different resistance genes. At present, the world's breeders widely practice polygenic (gene pyramiding) resistance instead of the traditional monogenic one. Cultivation of varieties obtained by crossing resistant varieties with susceptible ones using molecular control of gene transfer at each stage, which can serve as a highly effective method for combating blast. The genetic heterogeneity of M. grisea should be considered when screening for blast-resistant rice genotypes using morphological, phytopathological and molecular characterization analyses.