Study On Production And Application Of Aschersonia From Aleurotrachelus Camelliae Kuwana

Destructiveness and resistance of whitefly pest species have encouraged the development of alternative eco-friendly strategy,biological pesticides,for the management of noxious insect pests.In view of the advantages of Aschersonia spp.and the stock colonies we have,the objectives of the study here were:(1)To select a most efficient strain from 26 isolates of Aschersonia against Bemisia tabaci then to determine if the fungus selected is capable of infecting different instars of B.tabaci larvae and insecticidal capacity.(2)To optimize medium components for enhancement of hyphal growth and conidial production of target fungus by diphasic liquid-solid fermentation system using Response Surface Methodology.(3)To study the issue of formulation composition,interaction of formulation and inseticide,and biosafety of our fungus,and so on.Strain screening and test of insecticidal capacity Conidial suspensions for experiments were prepared with an aqueous solution of 0.05%Tween 80.Conidial concentration used to test the 2nd instar larvae in the experiment of strain screening was 107 conidia mL-1 and the concentrations of 108,107,106,105 and 104 conidia mL-1 were employed to infect each instar larvae in other experiments.The results indicated that most strains of Aschersonia could infect whitefly pest species and proved that A.placenta FJSM can parasitize B.tabaci larvae of different instars.Furthermore,in most cases,FJSM could fully complete its life cycle by sporulating on B.tabaci cadavers.The adults and eggs of Bemisia tabaci are the most resistant to fungus tested.However,the highest mortality of 3rd to 1st instars larvae post-inoculation ranged from 93%to 100%.Data of observation fit well to the time dose-mortality model,which indicate the significance of the TDM relationship of A.placenta FJSM to the B.tabaci larvae.The time-dose effects,the estimates of the LD50 and LT50 values,and the virulence of A.placenta FJSM for B.tabaci larvae of different instars demonstrated that A.placenta FJSM is a promising fungal agent for B.tabaci control.Optimization of diphasic liquid-solid fermentation system using ResponseSurface Methodology A culture medium for the mycelial growth production and sporulation of entomopathogenic fungus Aschersonia FJSM was optimized using response surface method(RSM).Interactions of medium components and the optimization of biphasic production system were studied using Box-Behnken design(BBD)with three levels and three variables.The coefficients of determination(R2)of 93.36%and 95.32%confirm that the models used in predicting the degree of growth and sporulation process has a very satisfactory and appropriate fitness with the test variables.The maximal yield of mycelial dry weight was 2.1524g per100 mL culture when the concentrations of glucose,vitamin B6 and MgSO4·7H2O was set at 31.4g/l,11.5mg/l,0.64g/l,respectively.In the second stage,the maximum production of conidia(5.1145×109 spores for each dish)could be achieved in the medium containing 33.8g/l millet,1.11g/1 KH2PO4 and 0.37g/l MgSO4.To verify the model,the calculated levels of the variables were used to cultivate the strain.The results showed that the mycelial dry weight was 2.1405 g/flask,which was close to the predicted value.The maximum spore yield(5.9132×109)obtained were higher than the predicted production,demonstrating the accuracy of the model and the superiority of the diphasic production system.Composition screening of Aschersonia FJSM formulation In order to improve the storage capacity and environmental stability of Aschersonia FJSM spores,a test was conducted to find a better formulation components using germination rates of Aschersonia conidia on raw materials.Moreover,the ratio of composition of oil formulation,water-in-oil formulation,suspending agents were obtained in the test.Biological compatiblity of fungal water-in-oil formulation and several inseticides Influences of each concentration of insecticides on germination rate of FJSM strain were tested firstly to find some insecticides compatible with our fungus,followed by their interaction tested.The results indicated that differences of inseticides biocompatible with fungus tested,Nitenpyram and Biphenthrin conducted a better performance.Especially,Nitenpyram with a low dose dissolved in fungal water-in-oil formulation can do the trick,with a mortality of 96%against B.tabaci.Test of Biosafety As biological agents,safety has been the focus in our concern and research.So acute takes orally tests with mice and acute percutaneous experiments using rat were carried out with FJSM biomass and its water-in-oil formulation to evaluate fungal safety to environment and non-target organisms in the study.During the period of 28d tested,weights of animals increased normally and there was no death,illustrated FJSM strain and its water-in-oil formulation belonging to low-toxic or actually non-toxic products.Moreover,there is no obvious influences on growth and death,irritation on skin or mucous membrane occurring in tested goldfish,which indicated that fungal FJSM strain and its water-in-oil formulation were biological safe products,with an applied potential.To sum up,the main achievements and innovations of this study are as follows.Firstly,TDM model was made to test insecticidal ability of candidate strain.Secondly,medium components of diphasic liquid-solid fermentation system were optimized using Response Surface Methodology.Thirdly,compositions of Aschersonia FJSM formulation were investigated in the test.Fourthly,biological compatibility of FJSM water-in-oil formulation and insecticide was revealed in the stydy.Finally,Biosafety of FJSM strain and its water-in-oil formulation was tested for the first time.In a word,FJSM strain and its water-in-oil formulation are safe,with a high application value.