[Identification and biological characterization of pathogen causing black spot of Pseudostellaria heterophylla in...

In Zherong county, Fujian province, the black spot of Pseudostellaria heterophylla often breaks out in the rainy season from April to June every year. As one of the main leaf diseases of P. heterophylla, black spot seriously affects the yield and quality of the medicinal material. To identify and characterize the pathogens causing black spot, we isolated the pathogens, identified them as a species of Alternaria according to Koch's postulates, and then tested their pathogenicity and biological characteristics. The results showed that the pathogens causing P. heterophylla black spot were A. gaisen, as evidenced by the similar colony morphology, spore characteristics, sporulation phenotype, and the same clade with A. gaisen on the phylogenetic tree(the maximum likelihood support rate of 100% and the Bayesian posterior probability of 1.00) built based on the tandem sequences of ITS, tef1, gapdh, endoPG, Alta1, OPA10-2, and KOG1077. The optimum conditions for mycelial growth of the pathogen were 25 ℃, pH 5-8, and 24 h dark culture. The lethal conditions for mycelia and spores were both treatment at 50 ℃ for 10 min. We reported for the first time the A. gaisen-caused black spot of P. heterophylla. The results could provide a theoretical basis for the diagnosis and control of P. heterophylla leaf spot diseases.