Pathogen identification and screening of fungicides against Pseudostellaria heterophylla(Miq.) Pax leaf spot

【Objective】 In order to identify the pathogen species of Pseudostellaria heterophylla(Miq.) Pax leaf spot in Shibing, Guizhou, and to explore the indoor inhibitory activity of six fungicides against the pathogen, so as to provide reference for field fungicide control.【Method】 The pathogen were isolated and purified from diseased leaves wit typical leaf spot systems by tissue isolation method, and the pathogen were verified according to Koch's rule. Combined with morphological observation and phylogenetic tree based on ITS, tef1, LSU, SSU, GAPDH and rpb2 genes, the pathogenwere identified, and the indoor toxicity of six common fungicides(35% tebuconazole·tebuconazole SC, 43% fluorobacterium·oximeryl ester SC, 75% oximex·tebuconazole WG, 60% azolethenyl WG, 37% difenoconazole WG and 30% benzopropiconazole EC) to the pathogen was determined by mycelial growth rate method.【Results】 Alteraria tenuissima was the pathogen causing the leaf spot disease of P. heterophylla in Shibing, Guizhou, and the strain number was TZSYB1. The results of indoor toxicity test showed that the six fungicides had certain inhibitory effect on the mycelial growth of TZSYB1. Among them, 30% propiconazole EC had the strongest inhibitory activity with Moderate inhibitory concentration(EC50) of 10.81 μg/mL, followed by 37% difenoconazole WG, and EC50 was 21.31 μg/mL, then was 43% fluorobactam·oxime ester SC, which EC50 was 27.31% μg/mL.【Conclusion】 The pathogen of P. heterophylla leaf spot in Shibing, Guizhou is A. tenuissima. 30% propiconazole EC, 37% difenoconazole WG and 43% fluorobacilli·oxime ester SC can be selected for further field control.