New Researches in Biotechnology - Facultatea de Biotehnologii ...

Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011AN ANALYSIS OF THE EFFECT OF TEMPERATURE ON THEQUANTITY OF BT TOXIN IN COTTON VARIETIES1. Universitatea de Stiinte Agronomice si Medicina Veterinara, Bucuresti, Romania2. University of Agriculture, Faisalabad, PakistanMUHAMMAD SAJJAD ALIi 1 , INTEZAR ALI 2Abstract. The expression of Bt transgene in cotton cultivars is dependent upon a host of factors.Extreme variations in temperature not only affect overall plant vigour and growth but the expressionof Cry1Ac gene is also compromised. The expression of Bt content correlated with temperature wasquantified in six cotton varieties during the cotton year 2010-2011. The results indicate a decline inexpression of Cry1Ac over temperature independent of the hybrid genotype. The situation necessitatesa post commercialization monitoring of the formally approved cotton varieties.Keywords: Cry toxin; quantity; temperature; correlation1. INTRODUCTIONBt cotton was developed to thwart the bollworm’s attack and during the last couple ofyears, there has been a steady growth in area covered by Bt cotton varieties in Punjab(figure 1).If on one hand, there is an increase in the adoption of Bt technology, there arealso many Bt varieties of unknown parent germplasm.The expression of Bt toxin is dependent upon a host of factors including parent germplasm,plant parts, availability of macronutrients especially nitrogen and changes in temperature.According to the work done in India, the expression of toxin in boll-rind, squares and in theovary of flowers was found below the threshold of 1.8µg/g ,the amount considered as LD 99(Kranthi et al., 2005).A high dose expression of Bt toxin ensures the durability of Bt technology and it isimportant that the foliar plant parts express this endotoxin in sufficient quantities to causemaximum mortality of the target pests i.e. Helicoverpa armigera (Hubner), Earias vitella(Fabricius) and Pectinophora gossypiella.The first instar of these target pests completesdevelopment on leaves chewing the tender foliar tissues. An enhanced quantity of Btendotoxin, therefore, in leaves is desirable in domestically developed and commercializedBt cotton varieties.However, the temperature extremes affect the plant vigour leading to a decrease inproduction of Bt endotoxin. The expression of Cry1Ac in Bollards due to temperaturevariations have been found varying and correlated with the survival of target pests (Olsen etal., 2005).The present study was designed in order to verify the uniformity of optimumexpression of Bt toxin with temperature variations in commonly commercialized cottonvarieties during the cotton season 2010-2011. It was necessary because earlier research hasshown a variance of Bt toxin in illegal varieties commonly found in farmers’ fields.15