Development of Plants Resistant to Insect Pests using Gene Manipulation

Damage to pasture plants caused by insect pests reduces the supply of feed for grassland animal production. In addition, the use of chemical insecticides for the control of pasture pests is undesirable for reasons of high cost and possible damage to the environment. One way to overcome these limitations is 10 utilize a recent development. in plant molecular biology which has seen the incorporation of cloned genes that confer insect _pest resistance into crop plants. To date, the most widely used genes for this purpose are those coding for insecticidal proteins from the bacterium Bacillus thuringiensis, and for inhibitors of protein digestion. However, other possible insect-resistance factors, including carbohydrale-digeslion inhibitors, lectins, feeding deterrents and insect peptide hormones, are also under investigation. A detailed knowledge of the specificity and molecular mode of action of these factors on insects is required for the implementation of a multigcne strategy to produce transgenic plants wilh durable insect pest resistance. Here we describe progress in the development of transgenic plants resistant to insect pests, with particular emphasis on our efforts to identify and manipulate genes that confer resistance to pests of the important forage legume, while clover.