New Researches in Biotechnology - Facultatea de Biotehnologii ...

Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 20113. RESULTS AND DISCUSSIONThe quantities of Bt toxin determined over the growing season are expressed below (table1).Table 1: Variation in the quantity of Bt toxin over the growing seasonMeanTemperature37 0 C 39 0 C 36 0 C 31 0 C 26 0 CVarieties 30DAP 70 DAP 100 DAP 130 DAP160DAPAA802 0.921 0.755 0.672 0.546 0.541MG6 0.915 0.764 0.722 0.548 0.514IR3701 0.924 0.76 0.681 0.546 0.523AA703 0.92 0.749 0.716 0.548 0.521FH113 0.924 0.765 0.727 0.546 0.527IR1524 0.913 0.756 0.657 0.549 0.506GH2035 0.912 0.765 0.673 0.543 0.504FH114 0.928 0.744 0.636 0.544 0.519N121 0.924 0.743 0.634 0.548 0.516The trend of change in concentration of Bt toxin related with temperature shows the highestproductivity at 37 0 C which declines onwards with an increase in temperature (figure2).The Bt toxin concentration is expressed in µg/g.Bt toxin concentration ranged between0.930—0.510 µg/g. The maximum level of Bt protein was produced at 30DAP whileminimum being at 160 DAP. The concentration of Bt content is tapered off towards the endof the growing period.At 37 0 C, i.e. at 30DAP, the varieties produced the highest quantity of toxin.The juveniletissues produced the maximum effect.However, at this stage the bollworms do not infest thefield as they appear later in the crop season at about 80-100 DAP. At 26 0 C (160DAP), theplants had the favorable temperature for growth and mature plants produced Bt toxinsufficiently. However, the graph clearly indicates that at no growth stage, no plant variety atany temperature range produced Bt toxin high enough to cause 95% mortality of targetpests (high dose strategy).Illegal varieties produced by random crossing of Bollard varietieswith local high yielding cultivars not only cause an economic loss to farmers (as the Btseeds are priced higher than non Bt); but also cause the survival of target pest individuals.The resistance evolution case has not yet been observed in Pakistani cotton fields as noresearch report indicates so. Pakistani cotton experts are of the view that the resistanceevolution in target pests due to less-than-optimal toxin concentration is not feasible(Sharma, 2009). The farmers have small holdings and due to adjacent fields of differentcrop plants, target pests do not survive due to host unavailability in vicinity. However, inmany cotton areas especially nearby cities, there is a trend of vegetable growing nearbycotton fields. The migrating surviving pests may find ochra, brinjal and cauliflower asalternate hosts for development.17