Against the grain: safeguarding rice from rice blast disease

Rice is the staple diet of more than three billion people. Yields must double over the next 40 years if we are to sustain the nutritional needs of the ever-expanding global population. Between 10% and 30% of the annual rice harvest is lost due to infection by the rice blast fungus Magnaporthe oryzae. Evaluation of genetic and virulence diversity of blast populations with diagnostic markers will aid disease management. We review the M. oryzae species-specific and cultivar-specific avirulence determinants and evaluate efforts towards generating durable and broad-spectrum resistance in single resistant cultivars or mixtures. We consider modern usage of fungicides and plant defence activators, assess the usefulness of biological control and categorize current approaches towards blast-tolerant genetically modified rice. Rice is the staple diet of more than three billion people. Yields must double over the next 40 years if we are to sustain the nutritional needs of the ever-expanding global population. Between 10% and 30% of the annual rice harvest is lost due to infection by the rice blast fungus Magnaporthe oryzae. Evaluation of genetic and virulence diversity of blast populations with diagnostic markers will aid disease management. We review the M. oryzae species-specific and cultivar-specific avirulence determinants and evaluate efforts towards generating durable and broad-spectrum resistance in single resistant cultivars or mixtures. We consider modern usage of fungicides and plant defence activators, assess the usefulness of biological control and categorize current approaches towards blast-tolerant genetically modified rice. pathogen isolate unable/able to cause disease on a plant cultivar that carries a single major resistance gene. disease resistance against a spectrum of pathogens, or disease resistance to all strains of a pathogen. resistance that remains effective during its prolonged and widespread use in an environment favourable to the pathogen or disease spread. when population numbers are reduced to a level insufficient to sustain diversity in the population. rapid, localized cell death in the host induced by the pathogen. plant resistance conferred by the interaction between an isolate-specific avirulence gene in the pathogen with a cultivar-specific resistance gene in the host plant. targeted deployment of disease resistance genes effective against the virulence spectrum of all lineages of pathogen populations in a geographic region. fusion of haploid nuclei in a heterokaryon to form a diploid nucleus, resulting in chromosomal exchange due to mitotic crossover followed by haploidization. quantitative resistance that allows some limited pathogen infection and is controlled by more than one dominant or recessive resistance genes. The effect is additive. contains isolates that are pathogenic on the same host species or on the same host cultivars of the same species. completion of multiple infection cycles in a given growing season. inhibitors of mitochondrial respiration at the quinol site (QO) of cytochrome b in the mitochondrial bc(1) complex. chromosomal location of a gene that affects a quantitative trait. random amplification of polymorphic DNA. PCR-amplifying fragments of repetitive elements. restriction fragment length polymorphism. activated by local necrosis caused by fungal, bacterial or viral infection or by synthetic plant activators. Results in heightened resistance in the whole plant to subsequent infection.