TRANSGENIC ELITE INDICA RICE PLANTS EXPRESSING CRYIAC DELTA-ENDOTOXINOF BACILLUS-THURINGIENSIS ARE RESISTANT AGAINST YELLOW STEM BORER (SCIRPOPHAGA INCERTULAS)

Generation of insect-resistant, transgenic crop plants by expression o f the insecticidal crystal protein (ICP) gene of Bacillus thuringiensi s (Bt) is a standard crop improvement approach, In such cases, adequat e expression of the most appropriate ICP against the target insect pes t of the crop species is desirable. It is also considered advantageous to generate Bt-transgenics with multiple toxin systems to control rap id development of pest resistance to the ICP, Larvae of yellow stem bo rer (YSB), Scirpophaga incertulas, a major lepidopteran insect pest of rice, cause massive losses of rice yield, Studies on insect feeding a nd on the binding properties of ICP to brush border membrane receptors in the midgut of YSB larvae revealed that cryI4b and cryI4e are two i ndividually suitable candidate genes for developing YSB-resistant rice , Programs were undertaken to develop Bt-transgenic rice with these IC P genes independently in a single cultivar, A cryIAe gene was reconstr ucted and placed under control of the maize ubiquitin 1 promoter, alon g with the first intron of the maize ubiquitin 1 gene, and the nos ter minator, Tile gene construct was delivered to embryogenic calli of IR6 4, an elite indica rice cultivar, using the particle bombardment metho d Six highly expressive independent transgenic ICP lines were identifi ed, Molecular analyses and insect-feeding assays of two such lines rev ealed that the transferred synthetic cryI4e gene was expressed stably in the T-2 generation of these lines and that the transgenic rice plan ts were highly toxic to YSB larvae and lessened the damage caused by t heir feeding.