射干叶斑病病原菌鉴定及室内防治药剂筛选OA

This study aimed to identify the pathogenic fungi responsible for leaf diseases in Belamcanda chinensis within the Chongqing region by integrating morphological examination with multi-gene phylogenetic analysis.The biological characteristics of the pathogen were assessed using hyphal growth rate measurements,while chemical and biological fungicides were evaluated through in vitro virulence assays.The pathogen was conclusively identified as Alternaria alternata.Infection manifested on mature B.chinensis leaves as circular or elliptical lesions characterized by greyish-white centers,dark brown margins,and yellow halos,which subsequently expanded into irregular shapes,leading to leaf necrosis and,in severe cases,defoliation.Biological characterization revealed optimal mycelial growth on potato sucrose agar,carrot agar,and potato dextrose agar(PDA),with PDA being most favorable for sporulation.Light conditions did not significantly affect mycelial growth;however,complete darkness enhanced spore production.Mycelial growth was supported across a pH range of 6 to 11,with maximal sporulation at pH 7.The optimal temperature for mycelial proliferation ranged from 25 to 30℃,while spore production peaked between 25 and 28℃.Carbon sources such as maltose,fructose,mannitol,glucose,and lactose accelerated mycelial growth,with mannitol yielding the highest spore counts.Nitrogen sources including beef extract,peptone,and glycine also promoted mycelial growth,with glycine resulting in the greatest spore production.In vitro toxicity assessment demonstrated that among seven chemical fungicides tested,400 g/L fluoxastrobin exhibited the most potent inhibitory effect,with an EC50 value of 0.016 8 μg/mL.Among seven biocidal agents,0.3％tetracycline showed the highest efficacy,with an EC50 of 0.167 μg/mL.These findings provide a scientific basis for the precise identification of A.alternata induced leaf spot in B.chinensis and inform the targeted application of effective control measures.