Pathogen identification and indoor fungicides screening of Houttuynia cordata Thumb. Anthracnose

【Objective】 To identify the pathogen and screen out effective control agents for anthracnose of Houttuynia cordata Thumb., so as to provide reference for field control of this disease.【Method】 Tissue separation method was used to isolate the pathogen of anthracnose of H. cordata in Lianghe Town, Dangyang City, Hubei Province. Pathogenicity of the pathogen was determined based on Koch's rule. The sequences of ITS, GAPDH, TUB2, ACT and CAL in the pathogen were amplified respectively. The pathogen was identified based on multi-gene sequence analysis and morphological characteristics. The biological characteristics of pathogen and indoor toxicity of 5 common fungicides against the pathogen were determined by the method of mycelial growth rate.【Result】 A total of 6 strains were isolated from diseased leaf samples, and the representative strain YXC26 was selected for morphological characteristics and pathogenicity determination. The pathogenicity test showed that YXC26 was the pathogen causing anthracnose of H. cordata Thumb. The strain YXC26 was identified as Colletotrichum gloeosporioides by morphological observation and multi-gene sequence analysis. The results of biological characteristics determination of strain YXC26 showed that the optimum pH was 6, the best carbon sources were maltose and glucose, and the best nitrogen sources were yeast extract and beef dipping powder. The lethal condition of mycelium was incubated at 53℃ for 10 min. Among the 5 tested agents, 50% carbendazim wettable powder (WP) had the best inhibitory effects on mycelial growth of strain YXC26, with EC₅₀ value of 0.04 mg/L, followed by 25% pyraclostrobin suspending concentration(SC), and its EC₅₀ value was 0.14 mg/L. The EC₅₀value of 62% pyrimidine· fludioxonil water dispersible granule(WDG) was 1.16 mg/L, and the inhibitory effect was acceptable. The EC₅₀ values of 30% methamphetamine aqueous solution(SL) and 250 g/L azoxystrobin SC both exceeded 30.00 mg/L, which had low inhibitory effect.【Conclusion】 The pathogen of anthracnose of H. cordata Thumb. in Lianghe Town, Dangyang City, Hubei Province was C. gloeosporioides. 50% carbendazim WP, 25% pyraclostrobin SC and 62% pyrimidine·fludioxonil WDG had excellent inhibitory effect on mycelial growth of C. gloeosporioides, which could be used as a candidate agent for anthracnose control of H. cordata Thumb. in the field.