Panax notoginseng round spot disease (PRSD), caused by Mycocentrospora acerina, is the main leaf disease occurring in cultured P. notoginseng. Aiming to find a safe and efficient control method for PRSD, we studied the disease characteristics of PRSD and the optimal growth conditions of M. acerina and evaluated the efficacy of rain-shelter cultivation in PRSD control. Moreover, we described M. acerina based on morphological characterization and molecular analyses (ITS, ACT, LSU, and TEF-1α). The optimum temperature for M. acerina conidial germination was found to be 14 to 22°C. Furthermore, leaf surface wetness for at least 4 h is required for conidial germination, and conidia can successfully infect P. notoginseng when the leaf wetness lasts for more than 8 h. Additionally, rainwater splashing determines the conidial transfection distance, which is less than 2 m. Finally, our study revealed that rain-shelter cultivation is an effective and simple physical prevention strategy to control PRSD, with an average efficacy of up to 100%.

Round spot is a destructive disease that limits of Panax notoginseng production in China. However, the genetic diversity of its etiological agent Mycocentrospora acerina has yet to be studied. In this work, firstly, we developed 32 M. acerina polymorphic microsatellite markers using MISA and CERVUS 3.0 and selected 14 for further analysis. Then, we studied the genetic diversity of 187 isolates collected from P. notoginseng round spot using simple sequence repeat markers and polyacrylamide gel electrophoresis. The genetic diversity ranged from 0.813 to 0.946, with 264 alleles detected at the 14 microsatellite loci. The expected average heterozygosity was 0.897.