[Identification, biological characterization, and fungicide screening of pathogen causing southern blight in Aster...

This study aims to clarify the species and biological characteristics of the pathogen causing southern blight in Aster tataricus and screen out effective fungicides for the prevention and control of this disease. We collected the typical diseased plants and sclerotia on soil surface for the isolation of the pathogen, and identified the pathogen based on morphological characteristics, molecular biological characteristics, and pathogenicity. Further, we evaluated the inhibitory effects of 12 fungicides on the pathogen by plate growth inhibition assay. In the diseased plants, watery brown spots first appeared at the stem base and then spread upward, which were covered with white mycelia and surrounded by white to yellow-brown sclerotia. From the diseased plants, 15 strains with consistent traits were isolated. The pathogen was identified as Athelia rolfsii based on morphological characteristics and ITS and TEF sequences. The pathogenicity test was carried out according to Koch's rule, which showed the disease symptoms consistent with those in the field. The pathogen presented the optimum growth at 28-30 ℃, pH 5-8, and full darkness. The preliminary indoor screening demonstrated that four chemical fungicides(taifujin, hymexazol, flusilazole, and lime-sulphur-synthelic-solution), two botanical fungiticides(ethylicin and garlic oil), and a microbial agent(Bacillus subtilis) had good inhibitory effects on A. rolfsii. The results of gradient inhibition experiments showed that B. subtilis, flusilazole, and ethylicin had stronger inhibitory activity. The further in vivo screening indicated that ethylicin can be used as the main fungicide for the prevention and treatment of southern blight in A. tataricus.