Activity Analysis Of Entomopathogenic Fungi And Novel Protein Elicitor (PeBb1) Against Myzus Persicae

Green peach aphid,Myzus persicae?Hemiptera:Aphididae?,is an economically important pest of a wide range of crops all over the world.Entomopathogenic fungi such as Beauveria bassiana,Lecanicillium lecanii and Metarhizium anisopliae are effective,environment-friendly and target-specific biocontrol tools against many sucking insect pest species.This research work encompasses in-vitro pathogenicity of two strains of B.bassiana?BB-72 and BB-252?and one strain of L.lecanii?V-4?against green peach aphid.Using a leaf-dip method,three bioassays were conducted with filtrate and conidial formulations of BB-72,BB-252 and V-4 and their binary combinations.In filtrate bioassays,2 mL fungal filtrate of each strain was used while in conidial bioassays,three different concentrations(i.e.,1×10⁶,1×10⁷ and 1×10⁸ conidia mL^-1)of each fungal strain were used and in binary combination bioassays,LC₅₀ and LC₃₃ of these fungal strains were evaluated.Results revealed maximum pathogenicity against test aphids at 10^th day of all treatments.Both strains of B.bassiana?BB-72 and BB-252?exhibited higher mortality of aphids?up to 95and 91%,respectively?than L.lecanii?V-4?strain?87%?.Likewise,binary combinations of BB-72 and BB-252 strains showed significantly higher aphid mortality?94%?than other combinations,which suggesting that both strains of B.bassiana?i.e.,BB-72 and BB-252?are mutually compatible and can be utilized together as new biocontrol tools against destructive insect pests such as M.persicae.To this end,we report here a novel elicitor protein PeBb1 extracted from B.bassiana BB-72?ARSEF 2860?strain exhibiting induced system resistance?ISR?in Brassica rapa subsp.pekinensis against green peach aphid M.persicae.This 534 bp elicitor protein encodes a polypeptide of 177 amino acids with a molecular mass of 19 kDa and induced a hypersensitive response?HR?necrosis in leaves of Nicotiana tabacum.In-vitro bioassays were performed with three different concentrations of this PeBb1 protein(i.e.,26,35,52?g ml^-1)against green peach aphids on B.rapa plants.Protein treatments were applied on B.rapa at 4-leaf stage and newly emerged?0–6 h old?adult aphids were exposed to the treated leaves.Results showed significant?p<0.05?and pronounced sub-lethal effects of exogenous application of PeBb1 elicitor on M.persicae.By the application of PeBb1 elicitor protein,aphids'fecundity was significantly reduced as compared to control plants.Gene expression analysis done with RT-qPCR revealed that many plant defense associated genes,i.e.,ethylene?ET?-responsive and jasmonic acid?JA?-responsive genes,were up-regulated in the PeBb1 treated plants.Overall,this study not only demonstrates the pathogenicity potential of novel strains of entomopathogenic fungi but also isolated a novel protein elicitor that could trigger plant systemic resistance against M.persicae.