| Peach aphid(Myzus persicae)is a kind of agricultural pest,which is one of the most common and most hardestto control in China.It can infect more than 400 hosts and all the plants in facility cultivation.It can also cause sooty mold and spread the viral disease among the plants,resulting in a substantial reduction in crop production.With the continuous development of China's agriculture,the advantages of a variety of single cropping,high-density continuous cropping,farming environment deterioration,as well as the massive abuse of chemical insecticides leaded to aphid resistance increasing year by year.In this paper,we collected the dead insects in Qinling virgin forest,selected the biocontrol fungi with high pathogenicity to peach aphids,identified the strains we collected and optimized the liquid culture conditions.The main research results were as follows:In this study,101 dead insects were collected from the soil of the Qinling Mountains in Shanxi Province,including 4 Classes 9 Orders,such as Insecta,Diplopoda,Chilopoda and Arachnoidea.There were 5 Orders belonging to Insecta.A total of 50 strains of fungal strains were obtained by isolation and purification.The initial isolates was numbered 1-50.The number of fungal isolates isolated from Insecta insects was 44,accounting for 88% of the total strains.A preliminary screening of pathogenic isolates was carried out by inoculating peach aphids in the untreated cabbage.A total of 45 pathogenic isolates were selected from all the strains,10 isolates with cumulative mortality and the rate of insectsreaching 30% were screened and the BQ-63,which had the strongest infectivity to peach aphids.The optimum spore concentration of BQ-63 was screened,which showing the cumulative mortality,corrected mortality and the muscardine cadaver rate were highest when the spore concentration was 108 conidia mL-1,as 89.53%,90.10% and 89.84 %,respectively.In this study,strain BQ-63 was identified by morphological identification and molecular identification.Based on the identification key of ‘insect fungi',the fungus was identified as Beauveria.The amplicon size18 S rDNA and ITSsequences were approximately1300 bp and 547 bp,respectively.BLAST analysis confirmed the identity of the fungus,showing 100% similarity toBeauveria bassiana,and the GenBank accession numbers were KU240022 and KU240023.The phylogenetic tree constructed by 18 S rDNA and ITS sequences showed that the strain clustered within a clade comprising reference isolates ofB.bassiana,which showing strain BQ-63 was identified as B.bassiana.At the same time,the growth status and sporulation rate of strain BQ-63 were tested.The strain BQ-63 was cultured on PDA,the colony diameter reached42.15 mm on 7th day,and the amount of sporulation was measured on 15 th day reaching 3.65 × 108 spores/dishand the sporulation rate was higher.In this study,single factor variable analysis was used to determine the liquid culture conditions of strain BQ-63,such as carbon source,nitrogen source,trace element and pH based on the liquid culture medium.The final culture conditions were as follows: 30 g/L glucose as carbon source,15 g/L yeast leaching powder as nitrogen source,adding 0.1 g/L K+,0.1 g/L Mg2+,0.2 g/L Mn2+ as trace element,and the pH is natural pH.After incubation for 4 days with these conditions,the spores were 6.44× 108 spores/mL,the dry weight of mycelium was 10.82 g/L.Alltheindex had significantly improved and the optimization is obvious.In this study,70% acetamiprid water dispersible granules,30% permethrin water emulsion,25% thiamethasone water dispersible granules,20% imidacloprid wettable powder,5% pyrethrin missible oil,0.5% veratridine soluble concentrate were selected to make a comparison with strain BQ-63 on control peach aphids.The results showed that the decrease rate of the insects was 89.8% and the control effect was 88.18% after treated by BQ-63 fermentation broth.It was lower than the result of 20% imidacloprid wettable powder and the difference between them was slight.Therefore,the BQ-63 on the control of peach aphids was safe and environmentally friendly.It was not easy to make the pest resistant and high economic efficiency with significant application value. |
PDF Full Text Request