| Isaria fumosorosea(Hyphomycetes)is one of the most important fungi.At present,it is mainly used to control agricultural pests such as Bemisia tabaci,aphids and thrips.Entomopathogenic fungi are made from living conidia,which are show to control pests and are not stable enough.This greatly restricts the industrialization development and application of fungal pesticides.Toxins from entomopathogenic fungi can not be affected by external factors such as environment,temperature and humidity.It is an important development direction of entomopathogenic fungi.The extraction,isolation,purification and structural identification of the entomogenic mycotoxins are important in understanding the pathogenicity and toxin production mechanism of entomogenous fungi.Bemisia tabaci(Gennadius)(Hemiptera:Aleyrodidae)as a serious pest of agricultural crops in different regions of the world,contains more than 36 cryptic species within a species complex.Direct damage of B.tabaci occurs as a result of sucking plant sap from the phloem,secreting honey dew which serves as a substrate for growth of sooty moulds.Management of MEAM1 B.tabaci has been dominated by the frequent used of broad spectrum conventional insecticides resulting in development of insecticide resistance.Tis injudicious use of chemicals leads to the intermission of natural biological control systems and outbreaks of B.tabaci.All these factors have necessitated research and development of environmentally secure,biodegradable and indigenous methods for insect pest management.Hence,the search for selective chemical constituents of naturally occurring entomopathogenic fungi based biopesticides can be a potential method to overcome environmental pollution and resistance problems.These studies were performed to screen out 15 different isolates of I.fumosorsea based on protein production in fermentation broth,production of crude toxin and different solvent extraction methods.Furthermore,the toxins extracted from 2 screened out isolates were identified through LC-Ms analysis and toxicity of these toxins was also observed against B.tabaci.The results of the study are as follows:Screening of 15 I.fumosorsea isolates:The mycelium yield and protein concentrations in fermentation broth of 15 I.fumosorsea isolates were determined after shake flask fermentation.The strain with the highest mycelia yield were SP502,SP535,SP504 having biomass contents of 1.167±0.049 g,0.891±0.039 g,0.799±0.120 g,respectively.The highest protein concentration in the fermentation broth of SP502,SP535 and SP483 were0.372±0.001 mg/mL,0.346±0.005 mg/mL,0.293±0.004 mg/mL,respectively.Screening of solvents toxin extarction:Three organic solvents were selected to extract the crude toxin produced by Isaria fumosorosea(15 isolates)under submerged fermentation.Protein concentrations of the organic phase obtained after extraction with different solvents were in following order;Ethyl acetate>Methanol>n-hexane.The total crude toxin contents obtained through different solvents were in following order;ethyl acetate>methanol>n-hexane.Identification of crude toxins extracted though different organic solvents:The crude toxins from fermentation broth of SP502 and SP535 extracted with ethyl acetate,methanol,and n-hexane were identified by HPLC-MS.The results showed that crude toxins contained toxins such as Beauvericin and Penicillin G(Benzylpenicillin)used in various fields,such as agriculture and medicine.Bioassay:The conidial suspension(1x10~7conidia/mL),fermentation broth,three organic residues extracted from fermantion broth and crude toxin from Isaria fumosorsea isolates(SP502 and SP535),were tested for their toxicity against the 2nd instars nymphs of Bemisia tabaci.a.The corrected mortality of Ethyl acetate and Methanol crude toxins was higher than the corrected mortality of caused by conidial suspension and fermentation broth treatments.b.The pathogenicity of I.fumosorsea isolate SP502 was higher than SP535. |
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