Rashid, B: Gene Pyramiding: An Approach Towards Sustainable

Gene pyramiding approach was used to produce transgenic cotton expressing two Bt genes for sustainable resistance. The vector construct pK2Ac contained Bt genes and nptII gene both driven by CaMV35S promoter, confers resistance to Kanamycin.Sonication-assisted Agrobacterium-mediated transformation system was used. Heliothis armigera 2nd instar larval mortality ranged 75-100% and Bt protein was quantified in the leaves of transgenic plants. Segregation showed inheritance pattern 3:1 and confirmed the stable inheritance and integration of transgenes. Resistance of the transgenic plants against activity of Heliothis armigera was measured as average number of boll damaged per plant. Height of the transgenic plants was reduced and average number of bolls was increased. Ginning out turn was improved and medium staple length and coarse fiber quality could be improved considering environmental and physiological factors. Stacking or pyramiding toxin genes that express toxins with different modes of action or binding characteristics at a high dose, offers a potential route for achieving sustainable development of resistance.