The Virulence Difference Of 10 Fungal Species Against Three Insect Species And The Regulation Of Gene Expression To Host Insect

Demand of biological control is increasing with the passage of time because it is relatively safe with minimum risk and hazards to environment and the non-target living organisms communities.It also can be applied inundatively as a control option.Recently,microbial pest control agents have been getting more focus over the other available control measures against the insect pest population.Among the entomopathogen microbes,entomopathogenic fungi holds an important position,compared to other microbes,such as viruses and bacteria,because in case of entomopathogenic fungi,it can easily penetrate in the insect body via insect cuticle passage,where as some other microbes need to be orally ingested in order to cause the infection.In response of fungal penetration through the cuticle,a series of biochemical interactions takes place inside the host inect body,where the entomopathogenic fungi follow the sequential movements trend towards the insect mortality,and in this case,finally insect mortality occurs via entomopathogenic fungi and in the whole process various biochemical and physiological processes are involved,some of them have already been described,but not all the queries has been completely addressed yet.The current study was designed to explicates the virulence and pathology of three important EPF fungal genera,Metarhizium,Isaria and the Beauveria as a possible alternate for the management of three different pest species,by using the Sitophilus oryzae,Myzus persicae and Acyrthosiphon pisum as an test insect models.In case of A.pisum,host insect defense enzyme activities were also determined and fungi interaction during the infection in insects.Results of the bioassay in general revealed that,tested fungi strains were to be pathogenic but the level of virulence varies in the tested insect species.In case of S.oryzae,as per initial screening,evaluated effective isolates were further tested for multiple dose response against the Sitophilus oryzae adults.The results clearly demonstrates the differences of pathogenicity among the tested isolates as well as the methods.LT₅₀ values of the potential isolates varies,ME-33,3.63±0.11 days,Qin-21 4.17±0.18 days while Qin-188.58±0.33 days respectively,at the high conidial dose rate of 1×10⁷/ml.over all among the tested isolates,Isaria was found to be most potent on Beauveria and Metarhizium in terms of high pathogenicity and the low LT₅₀ values.In case of tested sucking insect pests,aphids species M.persicae was found to be more susceptible over A.pisum and surprisingly again Isaria isolates proved to be highy pathogenic and it has clarified that pathogenicity directly links to conidial dose rate and the exposure time.Among the four tested EPFs isolates,I.fumosorosea?SP-535?and I.fumosorosea?G-800?comparatively proved more virulent with LC₅₀ and LC₉₀ values of 4.6×10⁴,5.2×10⁵ and1.47×10⁶,1.76×10⁸?against M.persicae?while 5.9×10⁵,7.8×10⁶ and 1.97×10⁸,3.30×10⁹ was observed in case of?A.pisum?,and the results about the different temperature regimes clearly determined that Isaria spp.isolates proved be virulent at the temperature 25?respectively.We also have then studied the profiles activity changes of some important key enzymes,antioxidative enzymes POD-Peroxidases,SOD-Superoxidase dismutase and the CAT-Catalase as well as we also have studied the detoxification enzymes profiles,GST-glutathionine S-transferase,CarE-Carboxylesterase and the AKP-Alkaline phosphate enzyme activity in A.pisum insect host.CAT activity was measured high on 12 hpi?P<0.05?for the?SP-535?and the activity suppressed lately.Similarly an increase in activity was found at 24 hpi for the?Qin-13?which has showed decreasing trend on later time points,in case of SOD,among the treatments down-regulation was observed at 12 hpi in?SP-535?as well as 24 and 48 hpi in?Qin-13?,overall here mixed activity trend was observed,In case of POD,gradual up-regulation was observed in case of?SP-535?,while in case of?Qin-13?,initially up-regulation and lately suppression in activity was found.In case of detoxification enzymes,GST enzyme activity was clearly suppressed or down-regulated by?SP-535?on all later time points except 12 hpi,while in case of Qin-13 initially some significant suppression,but lately up-regulation was founded.In case of CarE enzyme activity,suppression was observed in case of?SP-535?but not significant suppression was found in case of?Qin-13?,latstly in case of AKP,no significant suppression was found in activity in case of both isolates except at 12 hpi.Over all GST enzyme activity of virulent strain?SP-535?has showed significant reduce in enzyme activity where as other isolate didn't showed the significant suppression.Metarhizium isolate with less virulence has not much significant effect on the enzymes activity.Transcriptome data revealed that in total 279 genes were differentially expressed in our tested samples CK 60 hrs Vs Treatment?SP-535?60 hrs represents and among of them 52 genes up-regulated and 227 down-regulated,while in total 122 differentially expressed genes,and among of them 56 were up-regulated and 66 down regulated in the tested sample of CK 6hrs Vs Treatment?SP-535?6 hrs.In KEGG differentially expressed genes in our tested 60 hrs samples were found 74 and while in case of 6 hrs sample treatment only 18 genes were differentially expressed.Genes in KEGG pathways were also differentially expressed and among of them,Metabolisim of xenobiotic by cytochrome P450,Glutathione metabolism,Fatty acid biosynthesis,Fatty acid degradation,Glactose metabolism,Purine and Lysine metabolism genes were found to be differentially expressed.However,further studies were needed to understand the mechanisim of biochemical pathways in A.pisum.The study demonstrates that the different entomopathogenic fungal genus has varying level of virulence and pathogenicity,Difference in the virulence linked with the down-regulation of the selected enzymes and their encoded genes of the host insects.It's possibly to provide an important basis to understand the entomopathogenic fungi interaction with their host insects.