Discovery And Biocontrol Potential Of One Cordyceps Javanica Strain

In this paper,one high effective strain of entomopathogenic fungi Cordyceps javanica（Bally）Kepler,B.Shrestha & Spatafora,was screened from the insect and soil samples which collected in wooded mountain and farmland.Myzus persicae was used for bioassay.The strain was named Cordyceps javanica IJ-tg19,and preserved in the China General Microbiological Culture Collection Center with No.18566.The optimal culture conditions were determined by setting different medium,temperature,photoperiod,and p H.The results showed that C.javanica IJ-tg19 produced more spores on SMAY and MEA than Czperk,PSA,PDA,SDAY,and SDA,and the sporulation concentrations were 4.59 ×10⁷ spores/mL and 4.57 ×10⁷spores/mL.Meanwhile,strain IJ-tg19 on MEA had the largest colony diameter after 14 d,which was 43.03± 0.61 mm.Strain IJ-tg19 produced the most spores at 25 30℃,and the concentration was 3.25 ³.46 ×10⁷spores/mL.The maximum concentration of Strain IJ-tg19 was 14.27 ×10⁷ spores/mL at 24L:0D photoperiod.The optimal pH of Strain IJ-tg19 was 7,and the spore concentration was 4.77 ×10⁷ spores/mL.The sporulation of this strain was influenced when p H > or < 7.Therefore,the laboratory culture conditions of C.javanica IJ-tg19 was on MEA medium with pH 7 at 25°C and 24L: 0D photoperiod.According to the best fitting equation,Y=1.08519-(0.7732/(1+（X/193311）^3.67186)),we know that the rapid growth period of strain IJ-tg19 was1.32 2.82 d,and the strain got the fastest growth rate at 1.93 d.Finally,mycelium with a maximum dry weight of 0.773 g would be obtained.The spray method was used to test the insecticidal activity of C.javanica IJ-tg19 on Myzus persicae adult,Trialeurodes vaporariorum 3rd instar nymph,Plutella xylostella 3rd instar larvae,and Potosia brevitarisis 2nd instar larvae.Bioassay results showed that the corrected mortality rates of M.persicae adult,T.vaporariorum 3rd instar nymph,P.xylostella 3rd instar larvae were 100% when spores concentration of C.javanica IJ-tg19 was 1×10⁸ spores/mL,and the LT50 was 2.77 d,3.04 d,and 1.45 d respectively.The results indicating that C.javanica IJ-tg19 has strong pathogenicity to the above three pests,and has the strongest infestation ability against P.xylostella 3rd instar larva,but it has weak pathogenicity to P.brevitarisis 2nd instar larvae.This study found a new strain of entomopathogenic fungi,C.javanica IJ-tg19,determined its optimal culture conditions and pathogenicity to some pests,and proved its potential to be used for biological control.This study was a useful exploration of the excavation and utilization of native biocontrol resouces in Shanxi Province,laid a foundation for further research and was expected to become new development resourse to help pest control and sustainable management of organic agriculture.