Abstract
Rice blast is a devastating disease, caused by the fungal pathogen, Pyricularia oryzae. RNA interference (RNAi) is a novel crop protection method that could control rice blast disease. In this study, dsRNA (PyDCL2–863 bp) was synthesized for silencing of DCL2 transcript of P. oryzae and its efficacy was evaluated. Using slide culture method, P. oryzae mycelial growth was evaluated under different concentrations of PyDCL2-dsRNA molecules i.e. from 0.1 to 10 ng/µl. After 24 hours of incubation, microscopic observations showed abnormal growth with high hyphae branching and vesicle formation in P. oryzae of 10 ng/µl dsRNA-treated slide culture. Disease severity caused by P. oryzae on rice leaves was compared using the detached leaf method with different PyDCL2-dsRNA concentrations, i.e. from 0.1 to 10 ng/µl. It was found that a 10 ng/µl concentration of dsRNA molecules reduced rice blast disease severity by up to 13%. Under glasshouse conditions, PyDCL2-dsRNA was sprayed at 10 ng/µl concentration on rice plants at three-week-old seedlings and disease reduction of rice blast disease was 35.11% six days after dsRNA application compared to unsprayed control. In glasshouse trial, the dsRNA solution with 10 ng/µl concentration was able to perform gene silencing on DCL2 in P. oryzae until 3 days after application. These findings showed a potential for PyDCL2-dsRNA to be developed as a new biofungicide using RNAi-mediated approach for a sustainable disease management of rice blast.