Rice blast and control methods

Abstract

Rice infections caused by Magnaporthe grisea are a major disease that wreaks havoc in almost all rice-growing 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.