Magnaporthe oryzae and Its Pathotypes: A Potential Plant Pandemic Threat to Global Food Security

Abstract

Food security for the growing world population can be affected by many different socio-economic and food production variables including pest outbreaks. Plant disease epidemics historically played a significant role in the starvation and displacement of the world population. Despite huge progress made by researchers in managing diseases of staple commodities, the threat level remains very high, as disease-causing organisms adapt to new hosts, become more virulent by changing their genetic makeup, and show increased resistance against fungicide products. The history of blast disease, which affects one of the world’s staple foods, rice, goes back centuries and has been a continual problem for rice production worldwide with the recent inclusion of wheat blast. Extensive studies on the biology, pathogenicity, and population genetics of Maganaporthe oryzae (Synonym: Pyricularia oryzae), the causal agent of blast disease, have enriched our understanding of the potential threat that this pathogen poses to rice and wheat production, and therefore world food security. Based on host specificity, mating ability, and genetic relatedness, M. oryzae is divided into several subgroups or pathotypes (different crop-adapted lineages). The genome structure of M. oryzae, characterized by instability, parasexual recombination, and the presence of transposon elements, enabling this pathogen to evolve rapidly and jump from one host to another, has raised real concerns for scientists, growers, and food policy makers. All available options such as forecasting and mapping of disease and pathogen race distribution, early and reliable quick diagnostics, biological and chemical control measures, inclusion of cultivars with resistance genes, and development of blast-resistant variety using CRISPR-Cas genome editing should be considered and deployed as a package for successful control of M. oryzae.