Identification and herbicidal activity of pathogenic fungi against Avena fatua and safety to crops
[Objective]The study aimed to screen for biocontrol strains with high safety,low drug resistance and strong herbicidal activity,providing a new biocontrol strategy for the prevention and control of the pernicious weed Avena fatua in farmland.[Method]Leaves of natural-ly diseased Helianthus cucumerifo,Chenopodium hybridum,Alcea rosea and Hordeum vulgare plants were collected for the isolation and puri-fication of strains using tissue and single spore isolation methods.Strains with biocontrol potential were obtained through in vitro leaf assays(primary screening)and in vivo pot experiments(secondary screening).The strains were identified based on colony morphology observation and the use of the Internal Transcribed Spacer(ITS)and Elongation Factor-1 alpha(EF-1α/EF-2)genes.A phylogenetic tree was con-structed using MEGA 7.0 software.Strains with biocontrol potential were further tested on live A.fatua plants using spore suspensions of dif-ferent concentrations(101-104)to determine disease incidence,disease severity index and fresh weight efficacy.Finally,safety tests were conducted on main crops in Qinghai province(Brassic anapus'Qingza5',Triticum aestivum'Qingchun38',Hordeum vulgare'Kunlun18',Vicia faba'Qinghai9',Pisum sativum'Caoyuan224',Zea mays'Qingyu517'and some vegetables(Brassia campestris'Zhebai6',Solanum lycopersicum'Boyu368',Cucum issativus'Zhongnong5',Spinacia oleracea'Huabo1',Capsicum annuum'Zhongjiao4',Raphanus sativus'Chunbai2')to select the most suitable application conditions for the strains.[Result]Seven fungal strains with herbicidal activity against A.fatua were isolated from leaves of naturally diseased plants and named DT-YSB1,DT-04A2,DT-DYLC,DT-XRKA,DT-08C,DT-14A2 and DT-QKBD004A.Through in vitro leaf assays and greenhouse pot experiments,strain DT-QKBD004A was identified as having strong herbicidal activity against A.fatua.Its colony morphology resembled that of Fusarium species,and molecular identification using rDNA ITS and EF-1α(EF-1/EF-2)genes,along with phylogenetic analysis,confirmed it as F.avenaceum.Efficacy tests at different spore concentra-tions revealed that a concentration of 9.40 × 104 spores/mL of strain DT-QKBD004A achieved the best control efficacy against A.fatua,with disease incidence,disease severity index,and fresh weight efficacy ranging from 45.09％-89.48％,42.68-88.53,and 38.70％-88.42％,respectively.Crop safety tests showed that a concentration of 9.40 x 104 spores/mL of strain DT-QKBD004A was safe for broad bean,corn,Chinese cabbage,tomato,cucumber and pepper.[Conclusion]F.avenaceum DT-QKBD004A has strong pathogenicity to A.fat-ua and is safe to some crops.It has good application value and can provide a good biocontrol strain for the prevention and control of malignant weeds in farmland.
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