石斛组培污染枝孢菌的鉴定及其敏感性杀菌剂筛选OA

[Objective]The present paper aimed to identify the common fungal species that contaminated the tissue cultures of Dendrobium spp.and to screen for sensitive fungicides by evaluating their inhibitory effects in vivo.[Method]Fungal strains were isolated using the direct colony picking method from Dendrobium spp.tissue cultures media,and the morphological characteristics of their colonies and spores were ob-served.The ITS,EF1-α and RPB2 fragments were amplified from genomic DNA of isolated strains via PCR.The species of contaminating fun-gi were identified through PCR products sequencing and their sequences analysis.Additionally,indoor screening of fungicides was conducted against the isolated strains.[Result]The isolated strains SH-1 and SH-2 exhibited the same morphology as Cladosporium spp.,and their ITS and EF1-α sequences showed the highest identities 100％and 99.59％to C.asperulatum and C.guizhouense,respectively.Further phyloge-netic analysis based on ITS and EF1-α sequences indicated that SH-1 and SH-2 were respectively identified as C.asperulatum and C.guizhouense.Among the eight screened fungicides,the strain SH-1 showed the highest sensitivity to carbendazim and thiabendazole,while strain SH-2 was only sensitive to carbendazim.In contrast,procymidone showed the weakest inhibitory effect against both Cladosporium spp.,with no significant inhibition observed even at a concentration of 3 mg/L.The EC50 values of carbendazim for SH-1 and SH-2 were further de-termined to be 0.09 mg/L and 0.11 mg/L,respectively.Moreover,0.25 mg/L of carbendazim could completely inhibit the growth of both strains on PDA.[Conclusion]The study identifies that the fungal contaminants in tissue cultures of the D.officinale and the D.anosmum are C.asperulatum and C.guizhouense,respectively.Among the eight tested fungicides,carbendazim demonstrates the most effective inhibition a-gainst the two Cladosporium spp..The findings provide a scientific basis and practical guidance for effectively preventing and controlling fun-gal contamination in Dendrobium spp.tissue cultures production.