[Identification, biological characterization, and fungicide screening of pathogens causing leaf spot of Belamcanda chinensis].

The leaf spot of Belamcanda chinensis often appears in May to June and spreads rapidly during the flowering stage(July to September) in the cultivation fields, seriously affecting the yield and quality of B. chinensis. To identify and characterize the pathogens of the leaf spot, we isolated two species of Alternaria, identified them according to Koch's postulates, and tested their pathogenicity and biological characteristics. Furthermore, we determined the inhibitory effects of 6 chemical fungicides, 1 plant fungicide, and 3 microbial fungicides on the pathogens by using mycelial growth rate and plate confrontation method to select the appropriate control agents. The results showed that the two pathogens causing B. chinensis leaf spot were Alternaria tenuissima and A. alternata. The conidia of A. tenuissima often formed long chains with no or a few branches, while those of A. alternata often formed short branched chains. The optimum growth temperature of both A. tenuissima and A. alternata was 25 ℃. The two pathogens grew well in alkaline environment. The indoor fungicide screening experiments showed that 40% flusilazole had good inhibitory effects on the two pathogens, with the EC_(50) values of 12.42 mg·L~(-1) and 12.78 mg·L~(-1) for A. tenuissima and A. alternata, respectively. The results of this study provide a theoretical basis for the subsequent theoretical research and field control of B. chinensis leaf spot.

[Identification, biological characteristics, and control of pathogen causing southern blight of Pinellia ternata].

In summer in 2020, Pinellia ternata in many planting areas in Hubei suffered from serious southern blight, as manifested by the yellowing and wilted leaves and rotten tubers. This study aims to identify the pathogen, clarify the biological characteristics of the pathogen, and screen fungicides. To be specific, the pathogen was isolated, purified, and identified, and the pathogenicity was detected according to the Koch's postulates. Moreover, the biological characteristics of the pathogen were analyzed. Furthermore, PDA plates and seedlings were used to determine the most effective fungicides. The results showed that the mycelia of the pathogen were white and villous with silk luster, which produced a large number of white to black brown sclerotia. The pathogen was identified as Athelia rolfsii by morphological observation and molecular identification based on LSU and TEF gene sequences. The optimum growth conditions for A. rolfsii were 30 ℃ and pH 5-8, and the optimum conditions for the germination of sclerotia were 25 ℃ and pH 7-9. Bacillus subtilis, difenoconazole, and flusilazole were identified as effective fungicides with PDA, and their half maximal effective concentration(EC_(50)) was all less than 5 mg·L~(-1). The effective fungicides screened with the seedlings were hymexazol and difenoconazole. Based on the screening experiments, difenoconazole can be used as the main agent for the prevention and treatment of southern blight.

[Identification,biological characteristics and fungicide screening of pathogen of southern blight in Cynanchum stauntonii].

During the high-temperature and rainy season from June to October in 2017-2019,serious southern blight broke out in the Cynanchum stauntonii planting area in Tuanfeng county,Hubei province,which had a great impact on the yield and quality of medicinal materials. In this study,the pathogen of C. stauntonii was isolated,purified,and identified,and the pathogenicity was tested according to Koch's postulates. Meanwhile,the biological characteristics of the pathogen were analyzed. On this basis,the effective fungicides were screened in laboratory. Finally,the pathogen( BQ-1) was identified as Athelia rolfsii( Deuteromycotina,Basidiomycota,anamorph: Sclerotium rolfsii). The optimum growth conditions for BQ-1 were 25-30 ℃,p H 5-8,and alternating light and dark.The effective chemical fungicides were lime-sulphur-synthelic-solution( LSSS) and flusilazole,and the effective botanical fungicide was osthole. BQ-1 was highly homologous to the pathogen HS-1 of peanut southern blight,with the similarity of 18 S r DNA and TEF sequences at 99. 09%. The southern blight in C. stauntonii might be resulted from that in peanut. In the production of C. stauntonii,the following measures should be taken: avoiding rotation or neighboring with peanut,draining water from June to October to reduce humidity,and reasonably applying fungicides.

[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.