Establishment of a Rapid Detection Method for Rice Blast Fungus Based on One-Step Loop-Mediated Isothermal Amplification (LAMP).

Rice blast is one of the most serious diseases for rice, and controlling the filamentous fungus Magnaporthe oryzae that causes rice blast is crucial for global food security. Typically, early infected rice does not show symptoms. Therefore, the early diagnosis of rice blast is particularly important to avoid uncontrollable propagation of rice blast fungus. In the present work, a rapid and efficient loop-mediated isothermal amplification (LAMP) method was developed to detect the pathogen at the early infected stage of rice. The Alb1 superfamily hypothetical protein MGG_04322, a nuclear shuttling factor involved in ribosome and melanin biogenesis, was chosen as the target for designing the LAMP primers. The LAMP assay enabled rapid detection of as little as 10 pg of pure genomic DNA of M. oryzae. In addition, we established the quantitative LAMP (q-LAMP) detection system to quantify the conidia of rice blast fungus. The q-LAMP assay enabled rapid detection (within 35 min) of the fungal spores at a sensitivity of 3.2 spores/ml. In addition, the assay sets up the linearization formula of the standard curve as y = 0.3066 + 15.33x (where x = amplification of time), inferring that spore number = 100.60y. In addition, the q-LAMP assay was successfully used to detect the presence of the virulence strains of M. oryzae (wild type) in comparison with that of the two mutant strains by quantifying the biomass within host tissue. These results provide a useful and convenient tool for detecting M. oryzae that could be applied in the incubation period of rice blast before symptoms appear.