射干叶斑病病原菌的鉴定、生物学特性及其有效杀菌剂研究

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

射干叶斑病在射干栽培产区多有发生,常始发于5月—6月,于开花期(7月—9月)快速蔓延,对该药材产量及质量造成严重影响。为明确射干叶斑病病原菌种类及其生物学特性,该研究依据科赫法则分离纯化、鉴定出2种链格孢属致病真菌并进行致病性测定及生物学特性测定。同时,利用菌丝生长速率法及平板对峙培养法测定6种不同化学杀菌剂、1种植物源杀菌剂、3种微生物源杀菌剂对致病菌的抑制作用,筛选出合适的防治药剂。结果表明,有2种病原菌可导致射干叶斑病,分别为细极链格孢菌Alternaria tenuissima及交链格孢菌A.alternata。病原菌显微特征显示A.tenuissima产孢表型为分生孢子形成不分枝或少分枝长链,而A.alternata分生孢子则常形成树枝状分枝短链。A.tenuissima及A.alternata最适生长温度均为25℃;2种病原菌均在pH偏碱性环境中生长较好;经室内杀菌剂筛选实验可知,化学杀菌剂40%氟硅唑对2种病原菌均具有较好抑制效果,其中A.tenuissima、A.alternata的EC50分别为12.42、12.78 mg·L-1。该研究结果为射干叶斑病后续理论研究及田间病害防控提供了一定的理论依据。

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 EC50values of 12.42 mg·L-1and 12.78 mg·L-1for 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.