The Combination Of The Entomopathogenic Fungus Metarhizium Anisopliae With The Insecticide Suppresses Immunity Against Locusta Migratoria(Meyen)

Locusta migratoria isan important agricultural pest of crops and pastures in China.Metarhizium anisopliaeis a kind of important biological control agent against locustwidely,because of its strong pathogenicity,harmlessness to people,livestock and crops.In view ofenvironmental factors,spray method and preparation quality limited in the practical application,the process of Metarhizium anisopliaeeffect on insectis slow.To evaluate the synergism effect and elucidate the biochemical mechanisms of synergism reason,we used low dose of insecticides combination with Metarhizium anisopliae against Locusta migratoriain this experiment.The contents of this paper are as follows:1.Under the same feeding conditions,the purified population had higher hatchability,survival rate,oviposition,the net reproductive rate and the intrinsic rate of increase compared with the field population.The activities of general esterases?ESTs?,phenol oxidase?PO?,acetylcholinesterase?ACh E?,peroxidase?POD?and catalase?CAT?in the purified population were concentrated.Locusts of narrow genetic background wereused to study the immune of Pathogen.2.We found the synergisticinteractions of M.anisopliaein combination withcycloxaprid against L.migratoriafor 7 days at the ratio of 8:2 and 2:8.Synergisticinteractions were also found between M.anisopliaeand imidaclopridagainst L.migratoria.M.anisopliaein combination withmalathion or beta cypermethrin ormethoxyfenozidehave synergisticinteractionsat the ratio of 8:2against L.migratoria.Synergisticinteractions were also found between M.anisopliaeand chlorantraniliproleat the ratio of 8:2 and 5:5against L.migratoria.3.When M.anisopliaein combination withinsecticides against L.migratoriafor 7 days,we monitored the activities of 10 enzymes.We found that theincreased activity of Multi-function oxidases?MFO?could led to synergistic interactionswhen M.anisopliaein combination withcycloxapridor Imidacloprid respectively.The increased activity of MFO and PO could led to synergistic interactionswhen M.anisopliaein combination withmalathion.The increased activity of MFO and decreased activity of PO could led to synergistic interactionswhen M.anisopliaein combination withbeta cypermethrin.The increased activity of MFO,ESTs and ACh E could led to synergistic interactionswhen M.anisopliaein combination withmethoxyfenozide.4.We challenged L.migratoria with simultaneous doses of M.anisopliaeandchlorantraniliprole for 6 days and monitored the activities of 10 enzymes.Activities of GST,ESTs and PO decreased in the insect during the initial time period andthat ofsuperoxide dismutase?SOD?,CAT and POD decreased at a later time period post treatment.Whereas those of aryl acylamidase?AA?and chitinase?CHI?increased during the initial period and that of ACh E increased during a later time periodcould produce high mortality in locusts.Our results suggest that L.migratoria immunity to chlorantraniliprole and M.anisopliae was weakened bydecreasedactivities.Locust mortality increased as a result of synergism via a mechanism related to Ca²⁺ disruption in the hostwhen M.anisopliae in combination with chlorantraniliprole have synergistic interaction.5.In this experiment,M.anisopliaein combination withchlorantraniliprolesuppressed the expression of GNBP1 at the transcription and protein level in host recognization.Toll,d My D88,PPO1 and PPO2 also decreasedat the transcription level of Toll pathway signal transduction and prophenoloxidase-activating reaction.We speculatedthat GNBP1 and Toll might be the target of M.anisopliae in host.Our results establish a theoretical basis for the interaction between M.anisopliae and insecticides and should inform future studies investigating the mechanism by which M.anisopliae overcomes host immunity.