Expression of osa-miR7695 against the blast fungus Magnaporthe oryzae in Vietnamese rice cultivars

Magnaporthe oryzae causes rice blast disease, which leads to devastating yield losses in Vietnam and other rice-growing countries. Recent studies indicated that 30% of rice- growing areas are affected by rice blast disease. MicroRNAs (miRNAs) are short non-coding RNAs that are related to plant development and biotic stress tolerance. Osa-miR7695 as one of the common miRNAs, and its target the OsNramp6 gene were evaluated as factors that contribute to the pathogenic activity of different rice cultivars. The expression profile of microRNA osa-miR7695 was evaluated to identify blast resistance or susceptibility in rice cultivars. Results of RT-PCR and real-time qPCR indicated the presence of osa-miR7695 in most Oryzae sativa Indica group cultivars in Vietnam. Upregulation of osa-miR7695 observed in blast resistant rice cultivars at different infection time intervals was higher than in blast non-resistant rice cultivars. Expression of the OsNramp6 gene increased in blast non-resistant cultivars, particularly at 72 h post inoculation. Average Delta Ct values of osa-miR7695 in blast resistant rice cultivars were higher by approximately 4-fold than in blast non-resistant rice cultivars. Results suggested osa-miR7695 as a potential biomarker for microRNA based detection of blast resistance and non-resistance in Vietnamese rice cultivars to improve understanding of the biological role of microRNA in rice immunity.