金龟子绿僵菌MaHGM202303菌株对高温和紫外线的抗逆性及对草地贪夜蛾的毒力OA

[Objective]The aim of this study was to clarify the stress resistance of conidia of Metarhizium anisopliae MaHGM202303 strain,the optimal culture medium,and the virulence against Spodoptera frugiperda,so as to provide scientific basis for large-scale cultivation,selection of field application conditions,and green prevention and control of Spodoptera frugiperda.[Method]Using Metarhizium anisopliae MaHGM202303 strain as the test material,the colony growth rate,spore production,and conidial germination rate were determined by the plate culture method under different culture media(SMAY,SDAY,and PDA),temperature stress(water bath at 25,35,40,45,and 50 ℃ for 30 min),and ultraviolet stress(spores were irradiated with a 20 W ultraviolet lamp at a distance of 30 cm at 25 ℃ for 24,48,72,and 96 h).The virulence of the strain against the 2nd instar larvae of Spodoptera frugiperda was tested by the immersion method.[Result]SMAY medium was the optimal medium for MaHGM202303 strain.On this medium,the daily colony diameter increase and spore production reached 4.94 mm/d and 1.54×10 ⁷ CFU/mm² respectively after 11 d of culture.When 2nd instar larvae of Spodoptera frugiperda were inoculated with conidia of MaHGM202303 strain produced on dif-ferent media,there was no significant difference in spore production per larva(P>0.05,the same below).High tempera-tures above 35 ℃ greatly affected the conidial activity.The conidial survival rate after treatment at 35 ℃ for 30 min was 82.33％.Ultraviolet irradiation inhibited conidial activity,24 h of irradiation had no significant effect on conidial germina-tion,but after 48,72,and 96 h of irradiation,the germination rates decreased to 74.96％,63.54％,and 51.31％respec-tively.The virulence assay showed that the cumulative corrected mortalities of 2nd instar larvae at 3 and 9 d after inocula-tion with conidial suspensions of MaHGM202303 strain ranging from 1.0×104 to 1.0×108 CFU/mL were 6.78％-35.60％and 20.34％-86.72％respectively.The median lethal times(LT50)at conidial concentrations of 1.0×106,1.0×107,and 1.0×108 CFU/mL were 7.22,6.21,and 4.20 d respectively.The median lethal concentrations(LC50)at 7 and 11 d after inocu-lation were 1.17×107 and 1.35×105 CFU/mL respectively.[Conclusion]Metarhizium anisopliae MaHGM202303 strain shows strong virulence against 2nd instar larvae of Spodoptera frugiperda and has the potential to be a candidate strain for biological control of Spodoptera frugiperda.For field application,environmental temperature and ultraviolet radiation in-tensity should be comprehensively considered,and the application timing should be rationally selected to improve control efficacy.