Study On Protein Elicitor From Verticilium Lecanii To Inducing Resistance Against Megoura Japonica Matsumura On Phaseolus Vulgaris L.

Bean aphid,M.japonica Matsumura,is a dangerous insect pest of a wide range of crops in the world.Entomopathogenic fungus V.lecanii and B.bassiana are high effective,environment friendly,and target specific biological control tools against many sucking insect pest species.This study determined the effect of two strains of B.bassiana?B76 and B252?and two strains of V.lecanii?L2 and L5?against bean aphid.Three bioassays were conducted with filtrate and conidial formulations of B76,B252,L2 and L5 and their binary combinations?L2+B76,L2+B525,B76+L5,and L2+B76+B252+L5?.In the comparation bioassays of filtrate and conidia,2 mL fungal filtrate and conidia of each strain were used.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.Results revealed maximum pathogenicity against test aphids on the 8^th day of all treatments.Both strains of B76?85.3%?and L2?77.9%?exhibited higher aphid mortality than two strains of B252?66.0%?and L5?60.9%?with the highest concentration of 1×10⁸conidia mL^-1.Likewise,binary combinations of B76 and L2 strains showed significantly higher aphid mortality?90.5%?than other combinations,it suggested that both strains of B76 and L2 are mutually compatible and can be utilized together as new biological control tools against insect pests such as bean aphid.In the comparation test of filtrate and conidia,the result shows that the effect of different fungi filtrate against bean aphid was higher conidial treatments.A novel elicitor protein PevL1 was extracted from V.lecanii strain L2 exhibiting induced system resistance in P.vulgaris L.against bean aphid.This 402 bp elicitor protein encodes a polypeptide of 134amino acids with a molecular mass of 14.46 kDa and induced a hypersensitive response?HR?necrosis in leaves of Nicotiana tabacum.In-vitro bioassays were performed with three different concentrations of this PevL1 protein(i.e.,24.0,31.0,and 50.0?g mL^-1)against bean aphids on P.vulgaris L..Protein treatments were applied on P.vulgaris L.and newly emerged?0–6 h old?adult aphids were exposed to the treated leaves.The fecundity rate was significantly reduced by different concentrations of elicitors applied at different temperature regimes.The minimal number of offspring was recorded as 7.7 at 15 ^oC at a concentration of 50.0?g mL^-1.Aphids preferred to colonize buffer-treated plants?70%aphid?than elicitors-treated plants?30%aphid?.In addition,elicitor-treated plants exhibited an induced resistance against aphids as compared to buffer-treated?control?plants.Gene expression analysis done with RT-qPCR revealed that many plant defenses associated genes,i.e.,SA responsive and JA responsive genes,were up-regulated in the PevL1 treated plants.Overall,this study not only demonstrates the pathogenicity potential of entomopathogenic fungal strains but also isolated a novel protein elicitor that could trigger plant systemic resistance against bean aphid.