Wide-Spectrum Synergy Of Recombinant Enhancin

The enhancin named P96 is a part of the protein expressed by the full-length enhancin gene from Trichoplusia ni Granulovirus(TnGV) in Escherichia coli. As a new kind of biologic synergist,it has be primitively demonstrated that it can significantly increase the virulence of Bacillus thuringiensis(Bi) and Avermactins to Helicoverpa armigera.Based on that,further research was carried out armed at P96's scale of broad-spectrum. This research involved P96's debilitation on the pests's development, feeding and oviposition ,the P96's decomposition to peritrophic membrane (PM) in the midgut of lepidopterous larvae,and the rapid procedure to obtain resistant strain by single-pair-selection method.Evidently,the result was acceptable.The effects of recombinant enhancin P96 on the development and oviposition of cotton bollworm, H. armigera, were studied in the laboratory. The results showed that the larvae of cotton bollworm developed slowly significantly after treated with P96, and the weight of pupal survivals was declined remarkably by 4.90% - 5.21 % and the fecundity of adult survivals was lessen remarkably by 52.62% - 65.68%, compared with those of control. This strong debilitation of P96 on the development of cotton bollworm should be another synergy mechanism of recombinant enhancin.The PM of lepidopterous larvae prevents harmful things,including all kinds of pesticides,from getting into the blood of lepidopterous. According to SDS-PAGE, P96 could decompose PM in the midgut of the 5th instar larvae of cotton ballworm.During the scale of P96's concentration 1.9 105-1.9 106OBs/mL, invertebrate intestinal mucin (IIM) of PM was completely decomposed.With the decreasing of P96's concentration, IIM of PM got incompletely decomposed gradually.The P96's notable synergism for two pesticides to kill the resistant and the suspectible strain of H. armigera was observed.To Lambda-cyhalothrin,the synergy ratios were 2.53-fold and 3.38-fold respectively,and to Bt,those were 1.33-fold and1.72-fold, respectively.Based on population genetics, a procedure of single pair selection was devised for studying a method of rapid obtaining resistant strain.The original genarations being the same,the resistance to Bt was single pair selected in laboratory while the resistance to Lambda-cyhalothrin was mass selected .We studied the role of single pair selection on speeding up resistance selection to Bt in cotton ballwarm.After two genarations' selection,the resistance ratio to Bt increased to 2.87-fold,whereas the resistance ratio to Lambda-cyhalothrin only increased to 1.88-fold.The result shows that the single pair selection can greatly speed up cotton ball warm's resistance to Bt as well as to chemic pestcides,and it is beneficial for the resistance selection to alternate a few generations single pair selection in mass selection.