EVALUATION OF TRANSGENIC COTTON CULTIVARS CONTAINING CRY TOXINS FROM BACILLUS THURINGIENSIS AGAINST THRIPS

Abstract

Cotton (Gossypium hirsutum L.) is a significant fiber crop that is contributing 7 to 10% in the GDP of Pakistan. In the production of cotton, Pakistan is ranked at 4^th position among the major cotton growing countries. Various insect pests, especially sucking and chewing pests, attack cotton crop. Among the sucking pests, thrips (Thrips tabaci Lindeman) causes the most significant damage to cotton at seedling stage. Due to tremendous usage of insecticides, these pests have developed resistance against insecticides. Therefore, cultivation of resistant cotton varieties is the best tactic that can minimize the attack of thrips on this crop. In the present study, five Bt cotton varieties with different cry toxins were evaluated for their resistance/susceptible response to thrips. The cotton cultivars selected for this study were including four Bt cotton cultivars (two single and two double toxins) and one non-Bt cotton cultivar. The experiment was carried out under climatic conditions of Faisalabad, Pakistan. There was not any pronounced difference in thrips population on different Bt cotton cultivars either they were single or dual toxin gene cotton cultivars. MNH-186 and FH-141 showed decreasing trend in population of thrips with the passage of time as compared to other Bt cotton cultivars. The little variation in thrips population among the Bt cotton cultivars showed that all Bt cotton varieties had good control effect on the thrips population. Thrips population was insignificant with respect to leaf position i.e. upper, middle and lower leaves. Correlation study of thrips population with different environmental factors exhibited r values of -0.2213, 0.49837 and 0.41735 for temperature, humidity and rain fall, respectively.