Research On The Mechanism Of The Bt Strains Insectidal Activity Against Rice Planthopper

Rice planthoppers seriously threaten rice production and endanger food security,chemical reliance is heavily during the process of production control,cause environmental pollution and increase drug resistance of rice planthoppers.As an agricultural pest of sucking and sucking mouthparts,rice planthoppers feed on screens of rice and cannot feed on Bt on rice leaves.It is generally believed that the insecticidal specificity of Bt is a long-term coevolution of insects and Bt in nature.of.In the early stage of the laboratory,a strain with high insecticidal activity against rice planthoppers(IPPBIOTSUC1012,Bt1012)was found.Therefore,planthoppers could not directly feed on Bt.What is the specific insecticidal mechanism of Bt1012? Therefore,this study explored the action model of Bt1012 and rice planthoppers.(1)First,this study investigated the first key issue in the process of co-evolution.Since rice planthoppers cannot feed on Bt,the only source of co-evolution between the two is that the Bt1012 strain endogenously enters rice,thereby increasing the contact between the two.This study analyzed the endogenous status of the Bt1012 strain in the hosts of rice planthoppers(Oryza sativa).Laser confocal detection results showed that the green fluorescent protein-labeled strain Bt1012 could be endogenous to rice.(2)Since Bt1012 can endogenously enter rice,then can the rice planthoppers feed on the spores and crystals of Bt1012.First,we tested the spore width and crystal diameter(~740 nm,~810 nm)of the Bt1012 strain and found that the spores and crystals of the Bt1012 strain were similar to the diameter of the mouth of the rice planthopper(? 1 ?m).In order to further determine the feeding range of rice planthoppers,the fluorescence signals of the midgut of Laodelphax striatellus were detected by feeding fluorescent nanospheres of different diameters(100 nm,625 nm,and 1350 nm)of SBPH.100 nm microspheres can be taken,and only a few individuals can ingest 625 nm microsphere particles,indicating that the size of the particles that can be fed by the fly squirter is about 625 nm.Bacterial suspensions of Bt strain(HD73-)were found to have a mortality rate of more than 90% for Laodelphax striatellus,but only about 10% of the slugs were fed with a solution that removed the Bt strain HD73-spore(with a negative control.Consistently,the above results indicate that spores and crystals can cause death of Laodelphax striatellus.The cause of death was that the spore and crystal blocked the mouth of the rice planthoppers.(3)Laodelphax striatellus is unable to feed the crystal-spore of Bt,then the way Bt1012 strains to play function is that the crystals dissolve only when they are in vitro,and fed by L.striatellus.The results of crystal solubility analysis of Bt1012 showed that the Cry64Ba-Cry64 Ca insecticidal protein could be dissolved under neutral condition(PH = 7),and sucrose could promote its dissolution,which was different from other alkaline solutions required for the insecticidal protein.At the same time,Cry64 Ba and Cry64 Ca had strong insecticidal activity against rice planthoppers only when they were co-expressed.Cry64 Ba and Cry64 Ca expressed individually lost the insecticidal activity against rice planthoppers.(4)The binding experiments of Cry64Ba-Cry64 Ca protein,Cry78 Aa protein and BBMV of Laodelphax striatellus indicated that the specific binding sites of Cry78 Aa protein was found on the midgut BBMV of Laodelphax striatellus,and the specific binding site of Cry64Ba-Cry64 Ca protein was more than Cry78 Aa protein.The above research data show that in nature,the strain Bt1012 may endogenize in rice and express and dissolve Cry64 Ba and Cry64 Ca insecticidal proteins,which in turn affect the rice planthopper.In this process rice is an important medium for the interaction of Bt strains with insects.However,the interaction between this strain and rice and rice planthoppers,and whether rice can express Cry64 protein and be fed by SBPH need further study.