Effects Of Transgenic Cry1Ab/Cry1Ac Rice On The Biology And Main Enzymes In The Pink Stem Borer, Sesamia Inferens

The transgenic crylAb/crylAc rice SY63Bt and the untransgenic control rice SY63was used as material in this paper. The field and indoor experiments were conducted to explore the effect of main enzymes and biological facts on the pink stem borer, Sesamia inferens Walker, by cry1Ab/cry1Ac-transformed gene rice. The results show as follows:1. The results of field experiments for three years continuously indicated that the control effect of white head rate on cry1Ab/cry1Ac-transformed gene rice was significantly better than that on controls (p<0.05). The investigation of the pink stem borer, S. inferens ratio in harmed rice fields found that the ratio of pink stem borer in rice fields, no matter transgenic rice or ordinary rice, was in absolute advantage which was much higher than that of other species of stem borer.2. The effects of a cry1Ab/cry1Ac-transformed rice on the food consumption, growth and survival of the pink stem borer, S inferens larvae were measured in vitro bioassay. The result shows that the cumulative food consumption and the relative consumption rate of both3rd and5th instar larvae that fed on Bt rice were significant reduced, as compared with those on the control. After fed on Bt rice, the net growth of both3rd and5th instar larvae performed to be negative. The motality rate of larvae increased with the extension of feeding time, the corrected mortality of3rd instar larvae mostly reached100%, when the5th instar larvae was85%at the end of the experiment.3. The methods of alive feeding and biological tests were conducted to explore lethal and sublethal effect of the pink stem borer larvae in3rd and5th instar by feeding cry1Ab/cry1Ac-transformed gene rice. When3rd and5th instar larvae were feeding with transformed gene rice continuously, the motality rate of larvae increased with the extension of feeding time. However, when larvae in3rd and5th instar got into sublethal amount then the food was switched into ordinary rice, the motality rate achieved a certain value then stopped increasing, and the larvae could get into next stage with larvae duration extension. Some of larvae could pupate after sublethal treatment but total pupation rate was significantly lower than that of the control. The pupa weight and length was decreased but emergency rate of the one which already pupated was not changed much. Laying eggs amount of adults which emerged from young larvae was decreased but that of adults which emerged from older larvae was not affected significantly.4. The effects of transgenic Bt rice on the activities of three protective enzymes(SOD, CAT and POD) in the pink stem borer larvae were studied by assaying enzyme activities after the3rd and5th instar larvae were fed with stems of transgenic and non-transgenic rice (control) for different time. The results showed that SOD activity of the3rd instar larvae which were fed with Bt rice for24h was significantly higher by43.44%than that of control, then reached the minimum after48h. the POD activity of the3rd larvae which were fed with Bt rice reached the maximum after24h, and significantly higher by29.22%than that of control, then reached the minimum after48h which was significantly lower than that of control. the CAT activity of the3rd larvae increased by30.33%after fed Bt rice for4h, after48h, the CAT activity of the treated larvae decreased by27.01%than that of control. The SOD activity of the5th instar larvae was significantly higher than that of control after the larvae was fed on transgenic rice for4h and reached the minimum which was lower by31.62%than that of control after the larvae was fed for36h; the POD activity reached the maximum and raised by73.2%than that of control after the larvae was fed for8h then reached the minimum after36h; the CAT activity reached the maximum and raised by75.73%after the larvae was fed for4h and decreased by7.55%after fed for48h than that of control. The resistance level of the3rd instar was lower than the5th instar when treated by transgenic Bt rice for the reason that3rd instar itself had lower defense capability. In the initial stage of feeding, the enzyme activity of larvae were found rising for protecting larvae from toxic action of BT toxalbumin. The enzyme activity were determined as rapidly descending and the metabolize mechanism of larvae was disturbed along with extension of feeding time which caused the poisoning symptom and even death of larvae.5. Enzyme activities determination was conducted to study the effect of two detoxification enzymes’(AChE and GSTs) activity in the pink stem borer larvae by feeding crylAb/crylAc-transformed gene rice. The results indicated that the AChE and GSTs activity in3rd and5th instar larvae was affected by Bt protein after feeding transformed gene rice. The enzyme activity of5th instar larvae descend range was a little smaller than that of3rd larvae. After feeding with transformed gene rice for48hours, AChE activity of3rd instar larvae descended for64.64%and the GSTs activity descended for17.45%than the control; AChE activity of5th instar larvae descended for42.53%and GSTs activity of5th instar larvae was matched with control group after treatment. 6. The change of trypsin activity of the pink stem borer after feeding crylAb/crylAc-transformed gene rice indicated that the trypsin activity of3rd and5th instar larvae was lower than control group after treatment. The trypsin activity of3rd instar larvae was decreased with expansion of treatment time. After feeding transformed gene rice for48hours, the trypsin activity descended for62.74%in3rd instar larvae while that descended for38.46%in5th instar larvae which indicated that Bt protein affected younger larvae more obviously.