地毯草叶斑病病原菌鉴定和寄主范围测定

Identification and host range test of leaf spot pathogen of Axonopus compressus

2022年,在昆明市松华坝蔬菜基地发现大片地毯草(Axonopus compressus)上发生1种由未知病原菌引起的地毯草叶部病害,其病斑呈褐色近圆形或长条形。为明确其致病菌,并对该病原菌进行寄主范围测定和杀菌剂毒力测定。通过分离培养、形态学和多基因联合测序分析,结果表明,引起地毯草叶斑病的病原菌为玉米平脐蠕孢(Bipolaris zeae)。孢子液离体叶片接种21种经济作物及常见杂草,发现B.zeae还可侵染水稻(Oryza sativa)、玉米(Zea mays)、高粱(Sorghum bicolor)、小麦(Triticum aestivum)、薏苡(Coix lacryma-jobi)、棕叶狗尾草(Setaria palmifolia)、狗尾草(Setaria viridis)、野燕麦(Avena fatua)、黑麦草(Lolium perenne)、稗草(Echinochloa crusgalli)。7种杀菌剂对B.zeae毒力表现为苯醚甲环唑EC50最小(0.381 mg∙L^(-1)),其他毒力(EC50)由大到小依次为氟唑菌酰胺(0.988 mg∙L^(-1))、异菌脲(1.864 mg∙L^(-1))、代森锰锌(5.401 mg∙L^(-1))、甲基硫菌灵(930.572 mg∙L^(-1))、嘧菌酯(989.571 mg∙L^(-1))、百菌清(1547.315 mg∙L^(-1))。本研究明确了引起地毯草叶斑病的病原菌及其寄主范围,并筛选出了抑菌效果较好的杀菌剂,为该病害的诊断与防控提供了理论依据。

In 2022,an extensive outbreak of an unknown disease showing symptoms of brown,nearly round,or elongated spots on leaves was observed in the field of Axonopus compressus at the Songhuaba vegetable base in Kunming,Yunnan,China.To clarify the pathogenic species causing A.compressus leaf spot,the hypothetical pathogen was isolated and cultured,morphologically analyzed,multi-gene sequenced,and tested using Koch’s postulates.The results proved that the pathogen was confirmed as Bipolaris zeae.The host spectra of this pathogen were tested by spore suspension inocultaion.The results proved that it can infect twenty-one economically important crops and common weeds,including rice(Oryza sativa),maize(Zea mays),sorghum(Sorghum bicolor),wheat(Triticum aestivum),coix(Coix lacryma-jobi),palm grass(Setaria palmifolia),foxtail grass(Setaria viridis),wild oat(Avena fatua),ryegrass(Lolium perenne),and barnyard grass(Echinochloa crusgalli).Furthermore,the toxicity(EC50)of seven chemicals against B.zeae was tested on plates,revealing that difenoconazole(0.381 mg∙L^(-1))exhibited the highest efficacy in inhibiting its growth,followed by fluxapyroxad(0.988 mg∙L^(-1)),iprodione(1.864 mg∙L^(-1)),mancozeb(5.401 mg∙L^(-1)),thiophanate-methyl(930.572 mg∙L^(-1)),azoxystrobin(989.571 mg∙L^(-1)),and chlorothalonil(1547.315 mg∙L^(-1)).The pathogens and host range of A.compressus leaf spot were clarified,and the fungicides with good antibacterial effect were selected.This study provides a theoretical basis for the diagnosis and prevention of this disease.