Identification and biological characteristics of southern blight causing root rot on three medicine plants of Iridaceae in Dabie Mountains

In order to identify the species and biological characteristics of the pathogen of southern blight from three kinds of Chinese medicine of Iridaceae(Belamcanda chinensis, Iris tectorum and I. japonica) in Dabie Mountains, the isolation, identification, pathogenicity and biological characteristics of the pathogens were studied according to Koch's postulates. In addition, 9 chemical fungicides, 3 botanical fungicides and 5 microbial fungicides were used to evaluate their inhibition to the isolates in vitro. The results showed that all the strains(SG-Q, YW-Q, and HDH-Q) isolated and purified from the diseased plants of B. chinensis, I. tectorum and I. japonica, respectively, were identified as Sclerotium rolfsii through morphological observation and sequence aligement of 18 S rDNA, rDNA-ITS and TEF. Field observations showed that the intensity of the disease incidence of three Iridaceae plants was B. chinensis>I. japonica> I. tectorum, and the pathogenicity of the strains was SG-Q>YW-Q>HDH-Q. For biological characteristics, SG-Q strain was suitable for growth under the 12 h light/12 h dark cycle, with the optimal growth temperature of 30 ℃ and pH of 5. Among the 9 tested chemical fungicides, 29% lime sulphure and 10% flusilazole had stronger inhibitory effect on mycelia growth of SG-Q. For 3 botanical fungicides, 1% osthol, 20% eugenol and 0.5% berberine could effectively inhibt the mycelial growth of SG-Q and cause the morphological variation of the pathogen. For 5 microbial fungicides, Trichoderma harzianum and Bacillus subtilis had better inhibition on the mycelium growth of SG-Q.