The Biology And Pathology Of Striped Stem Borer,Chilo Suppressalis Fed On Bt Rice

The biology and pathology of striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae), fed on Bt rice were studied. The two Bt rice homozygous line i.e. KMDland KMD2 containing a synthetic crylAb gene from Bacillus thuringiensis Berliner, which gained by Zhejiang University and Ottawa University of Canada, and their parental untransformed control cultivar Xiushui 11, were used as the material in this study. The results show as follows:1 Impacts of Bt rice on the food consumption, growth and survival of striped stem borer larvae under different temperaturesThe Bt rice homozygous line i.e. KMD1 was tested in the laboratory for evaluating its effects on larval food consumption, growth and survival of striped stem borer. The food consumption and body weight growth as well as the survival of both 3rd and 5th instar larvae fed on Bt rice were significantly reduced, as compared with those on the control. The temperature showed no marked effect on both food consumption and body weight growth of larvae fed on Bt rice stems since the onset of 3rd instar, conversely had significant effects as since the initial stage of 5th instar. In contrast, the temperature did not distinctly influence the survival of both 3rd and 5th instar larvae. There was a linearly positive relationship between the corrected mortality of larvae and the accumulative amount of Bt rice tissues ingested by larvae.2 The lethal and sub-lethal effects of Bt rice on the larvae of striped stem borerThe lethal and sub-lethal effects of Bt rice line KMD1 was measured on the larvae of striped stem borer. The Bt rice line acted high toxic to the 1st, 3rd and 5th instar larvae. When larvae of the tested three instars continually fed on the transgenic rice stems, they extremely died and could not pupate, even though the 5th instar larva were able to survive for a long time. In contract, larvae fed on untransformed control rice stems after feeding Bt rice tissues for several time, had a lower mortality and could survive into the next instar or pupal stage, while showed no significant difference in development time from the control. The larvae of three tested instar, except the 1st instar, reared with the control tissues after feeding the transgenic tissues could pupate and then emerge. Their emergence percentage and laid egg number werenot lower than those of the control. As regard to body weight and body length of moths developed from the treated larvae, they were not significantly different from those of the control as the larvae were treated since the 3rd instar, whereas performed markedly different as treated since the 5th instar.3 Pathological effects of Bt rice on the larvae midgut of striped stem borerThe pathological changes of the larvae midgut of striped stem borer, after feeding with Bt rice line KMD1, was studied with electron microscopy. Ultrastructural investigations of the anterior midgut showed cellular alternations in larvae, such as swelling of mitochondria, endoplasmic reticulum, dilatation of intercellular spaces, fenestration or disorganization of the Golgi complex, concentric arrangement of rough endoplasmic reticulum. The initial infected organelles were mitochondria. As the pathological process went on, the upper portions of the cells swelled, and cytoplasm in these regions decreased in electronic density and other organelles were damaged to a certain degree, such as wiredraw of nucleus, condensation of nuclesr, and the increase of number of rough endoplasmic reticulum. As the infection proceeded still further, pathological changes in the mitochondrial abundant areas of basal membrane infoldings of columnar cells and cytoplasmic projections of goblet cells were obvious. The midgut epithelium cells disrupted and sloughed off from the basal membrane finally.4 Impacts of Bt rice on the cellular immunity of larvae of striped stem borerThe impacts of Bt rice line KMD1 on the cellular immunity of larvae of striped stem borer weree investigated. The results shown that Bt rice affected the hemocytes of 5...