Objective To achieve the rapid and effective differentiation and identification of M. medusae and M. larici-populina.

Methods In this study, several sets of primers for loop-mediated isothermal amplification (LAMP) were designed based on the 28S ribosomal DNA gene of the two rust fungi. The putative primers selected from experiments were employed for LAMP reactions, and for the specific detection with the controls of genomic DNA from M. medusae, M. larici-populina, Sawadaia tulasnei, Erysiphe paeoniae, Gymnosporangium asiaticum, Morchella esculenta and Flammulina velutipes. The initial LAMP reaction system was established firstly and then the reaction system components and reaction conditions were further optimized. Hydroxynaphthol blue dye (HNB) was supplied into the reaction system to realize visual detection. Finally the sensitivity of the detection system was determined by the lowest DNA substrate.

Results The results showed that the selected primers had specificity-species. The optimal Mg^{2 +} concentration in the 25 μL LAMP detection system for M. medusae was 6 mmol·L⁻¹, the optimal internal and external primer ratio was 8:1, and the optimal dNTPs concentration was 1.2 mmol·L⁻¹. Meanwhile, the correspondent case for M. larici-populina was 4 mmol·L⁻¹, 6:1 and 1 mmol·L⁻¹. And all reaction products could be clearly detected with 160 μM hydroxynaphthol blue dying（HNB）. The two rusts detection system can be visually determined at 61 ℃ for 30 min and 40 min, respectively, each corresponding to the lowest DNA substrate concentration of 34 fg·μL⁻¹ and 60 fg·μL⁻¹.

Conclusion Through establishing a visual LAMP-HNB detection system, M. medusae and M. larici-populina can be differentiated and identified by the LAMP technology. This study provides a technological support in practice for rapid identification and detection of the important poplar rust diseases.