Host Plant Resistance of Cotton genotypes. Australian cotton is attacked by a diversity of insect pests. While transgenic Bt cottons will increasingly provide control of Helicoverpa, conventional host plant resistance remains a valuable component for tolerance to other pests and to “support” the by enhancing background levels of resistance. This proposal sought to continue research on host plant resistance from the previous project (CSE59C Evaluation of Pest Resistance in Australian Cottons) through: (i) continued field and laboratory studies of a range of cotton genotypes; (ii) increased emphasis on sucking pest resistance, particularly aphids and mirids; and (iii) research on the biochemical changes in cotton associated with induced defences, compensation ability and the efficacy of transgenic cottons.