元宝枫翅果褐斑病病原鉴定、生物学特性及室内药剂毒力测定

Identification and biological characterization of the pathogen causing brown spot on samara of Acer truncatum Bunge and screening of effective fungicides

为明确引起元宝枫(Acer truncatum Bunge)翅果褐斑病的病原,采用组织分离法对采集自贵州省的翅果发病组织进行分离,进一步通过回接试验确定了YB26菌株是致病菌,可在元宝枫翅果上引起同田间一致的褐斑症状。通过形态学观察,结合ITS-Alt a1-GAPDH多基因系统发育分析,将引起元宝枫翅果褐斑病的病原鉴定为链格孢菌(Alternaria alternata)。通过测定A.alternata YB26菌株在不同碳源、氮源、温度、pH值、培养基和光照条件下的生长,明确了该病原菌的生物学特性,结果表明:甘露醇为碳源、牛肉膏为氮源、温度为28℃、pH=7、沙氏葡萄糖琼脂培养基(SDA)和全黑暗培养条件最适合其菌丝生长。通过测定7种杀菌剂对A.alternata YB26菌株的室内毒力,发现25%啶菌噁唑的抑菌效果最好,EC50为0.8323 mg·L^(-1)。本研究是对A.alternata引起元宝枫翅果褐斑病的首次报道,研究结果将为元宝枫翅果褐斑病病害诊断和科学防控提供依据。

To investigate the causal agent of samara brown spot occurred on Acer truncatum Bunge in Guiyang City,Guizhou Province,we collected diseased samara for pathogen isolation.YB26,a representative fungal strain causing the disease through pathogenicity test,was identified as Alternaria alternata based on combined results of morphological characteristics and multigene(rDNA⁃ITS,Alt a1 and GAPDH)phylogenetic analysis.Then the biological characteristics of A.alternata strain YB26 were determined by testing the mycelial growth rate under different carbon and nitrogen sources,temperatures,pH values,media and light conditions.The re⁃sults showed that the suitable conditions for vegetative growth of YB26 were mannitol as carbon source,beef ex⁃tract as nitrogen source,Sabouraud glucose agar(SDA)as culture medium,temperature of 28℃,pH value of 7,and incubation under darkness.Furthermore,the inhibitory effects of 7 fungicides against strain YB26 were tested,among which 25%pyrisoxazole had the best antifungal activity,with the EC50 value of 0.8323 mg·L^(⁃1).This is the first report of samara brown spot on A.truncatum caused by A.alternata.The results provide a basis for the diagnosis and control of the disease on A.truncatum.