Helping nature protect plants.

Helping nature protect plants

Many plants produce chemicals that stunt the growth of insects. Unfortunately for farmers, most of the more effective of these chemicals are not produced by cultivated crops. But chemists at the Agriculture Department's Western Regional Research Center in Albany, Calif., are working to change that.

Anthony C. Waiss and Carl A. Elliger have found that varieties of Physalis (a genus including the tomatillo and cape gooseberry) and of petunia contain chemicals that can dramatically stunt Heliothis zea -- also known, depending on the host, as tomato fruitworms, corn earworms or bollworms. The researchers extracted the active chemicals and added them to the fruitworms' diet for six days. Some of these chemicals were so potent that insects dining on them grew to just 3 to 10 percent of the weight of insects fed a pesticide-free diet.

Researchers have sought to isolate the genetic capacity to make such chemicals from plants that are related only distantly, if at all, to the cultivated crops, Waiss says, "because the further we can go away from the cultivated plant, the longer it will likely take that plant's predators to evolve resistance" to its new chemicals. But this also presents a challenge, he says, because such distantly related plants cannot be crossed using standard horticultural methods.

Their current approach -- protoplast fusion -- merges the contents of a cell from each selected genus, and then regenerates the hybrid. While they haven't developed a satisfactory hybrid yet, Waiss predicts it's just a matter of time. Ultimately, once the genes responsible for producing the stunting chemicals have been identified and mapped, Waiss says they can be spliced into the desired crop plant through recombinant DNA techniques. And a benefit in this approach to chemical insect control, he notes, is that the active agents should be present only in the leaves, not in the edible fruit.