Introduction of new traits into cotton through genetic engineering : insect resistance as example

The main goal of gene transfer into cotton is the development of insect-resistant varieties. The stakes are important since cotton protection against insects uses almost 24% of the world's chemical insecticides market, which is not without consequences on the environment. The first approach was to introduce and express in the cotton genome genes from the bacterium #Bacillus thuringiensis# (B.t.) which produces entomopathogenic toxins. The development of an efficient #Agrobacterium tumefaciens# mediated transformation system was the first step. The expression of #B.t.# genes was studied and synthetic genes more adapted to a plant genome have been constructed. Studies on their expression in cotton is underway. The second focus was to develop startegies that would minimize the risks of inducing insect resistance. The main approach is to associate several genes coding for entomopathogenic proteins with different modes of action. Genes encoding protease inhibitors were chosen. One possibility is to associate a #B.t.# gene and a gene encoding a protease inhibitor. Several protease inhibitors were tested in artificial diets on major pests of cotton. The corresponding genes have been introduced into the cotton genome. These various orientations of the research program will be presented. (Résumé d'auteur