Sustainable methods to control Pyricularia oryzae, the causal agent of rice blast disease.

By 2030, global rice production will need to increase to meet the demand of the growing world population. However, rice is severely affected by blast disease caused by the fungus Pyricularia oryzae, which accounts for 10-30% yield losses per year globally, thus posing a threat to the world’s most important food crop. The fungus can infect all parts of the rice plant, including leaves, nodes and pani-cle. In the early stages of the infection process, P. oryzae forms an infection struc-ture called appressorium to break the plant cuticle. After an initial biotrophic phase, the fungus kills plant cells thus leading to visible symptoms. Currently, several methods for the management of rice blast disease, such as agronomic practices, use of resistant cultivars and synthetic fungicides, are avail-able and can be exploited in an integrated management approach. However, de-spite some resistant rice varieties that have been developed by breeding pro-grams, P. oryzae is able to rapidly develop new races that overcome resistance genes. Furthermore, the continuous use of fungicides may be harmful to humans and environment and can increase the risk of appearance of resistant fungal races. Biological control using microbial agents or plant extracts with antimicrobial ac-tivity is therefore considered a possible alternative and sustainable approach to control rice blast disease. However, biological protection is difficult to achieve in the field as its effectiveness is variable, highly depending on formulations and climatic conditions. Because of these drawbacks, durable control of rice blast still represents a substantial challenge. Innovative strategies for the identification of new molecules for the sustainable protection of rice are thus highly desirable.