Use of Biological Stress as a Novel Strategy to Control the Rice Blast Disease

Magnaporthe oryzae, a hemibiotropic fungus, causes the devastating blast disease of rice, which results in an annual loss of about 15% of the rice produced globally, enough to feed more than 60 million people for a year. Different approached have been adopted to manage the infection, including the use of chemical fungicides. In this study, we analyzed the potentials of using biological stress to hinder the development and pathogenicity of the fungus, thereby controlling its spread and host infection. We induced cell wall/plasma membrane, oxidative and osmotic stresses in the fungus by growing it on media supplemented with 20% w/v SDS, 10 mM H2O2 and 1M NaCl, respectively. Under these stresses, we evaluated the vegetative growth, pathogenicity, conidiation and conidia morphology of the blast fungus. Our results revealed that the fungal vegetative growth was seriously hindered by the various biological stresses, with SDS exerting the most pronounced growth inhibition. Conidiation was completely abolished under osmotic stress while oxidative stress significantly reduced conidia production, compared to the unstressed group. However, no significant difference was observed in conidiation following treatment with SDS. We also found that the various stresses have no effect on the physical morphology of the fungal conidia, with the exception of NaClinduced stress that completely blocked conidiation. In the presence of the biological stress, the pathogenicity of M. oryzae has been dramatically affected. No development of disease lesion was observed on rice leaves infected with SDS- and H2O2-stressed fungi. A weak lesion was however observed on NaCl-treated fungus. These findings have revealed the crucial potential of biological stress in the control and management of the rice blast disease, which hold a great promise to sustaining the global food security.