ITHACA, N.Y. -- Biologists at Cornell and Washington universities have genetically engineered and successfully field tested rice plants that resist some of the most destructive insects as well as salt and drought damage. Technology for the transgenic rice plants, which incorporates genes from potato plants to resist insect damage and genes from barley plants to make them salt-and drought-tolerant, will be given to developing countries under provisions of a Rockefeller Foundation grant. Rights to the technology, which potentially can reduce crops losses by billions of dollars each year, will be sold in developed countries such as the United States and Japan.
Development of the insect-resistant rice, which was reported in the April 1996 issue of the journal Nature Biotechnology, marks the first time that useful genes were successfully transferred from a dicotyledonous plant, the potato, to rice, a monocotyedonous plant.
The potato genes cause rice plants to produce a protein that interferes with insects' digestive process whenever the plant is wounded by insects. Thus, insects such as the pink stem borer eat less, grow less quickly, and plant damage is reduced to tolerable levels. A barley gene enables rice plants to produce a protein that makes them salt- and drought-resistant so that they grow in saline conditions and recover quickly from dry conditions.
"These are capabilities that wild plants develop naturally over years of evolution, but we can't afford to wait for domestic rice varieties to evolve resistance to insect pests or drought," said Ray Wu, Cornell professor of biochemistry, molecular and cell biology, and leader of the international team that spliced other plant species' genes into rice. "Hundreds of millions of hungry people need this rice now, and the crop losses to insects, drought and increasing salinization of soils are devastating."
According to Gary Toenniessen, deputy director for agricultural sciences at the Rockefeller Foundation, Wu and his colleagues "have made a significant contribution toward meeting world food requirements by demonstrating that biotechnology can be used to enhance the rice plant's ability to defend itself against pests and stresses, without the use of expensive and sometimes detrimental inputs such as pesticides."
Development of transgenic rice with salt and drought tolerance was reported in the March 1996 issue of the journal Plant Physiology by Wu and by Deping Xu, Xiaolan Duan and Baiwang Wang, all researchers in Cornell's Section of Biochemistry, Molecular and Cell Biology, and by Bimei Hong, Tuan-Hua David Ho, researchers in Washington University's Department of Biology. Reporting their development of insect-resistant transgenic rice plants were Wu, Duan and Xu, as well as Xigang Li and Mahmoud Abo-El-Saad, both Cornell researchers, and Qingzhang Xue, a biologist at Zhejiang Agricultural University in Hangzhou, China.
The transgenic rice was developed with support from the Rockefeller Foundation's International Rice Biotechnology Program. That program funds some 40 laboratories in developed countries and another 80 in developing countries where scientists are trained to help their countries become more agriculturally self-sufficient.
Transgenic plants from both technologies are in advanced stages of testing, with large field tests scheduled this year in China. Commercial production of seed is about two years away, Wu estimated, but several companies have already signed licensing agreements to use the insect-resistance gene technology in other crops, including corn and wheat.
The genes from other plant species that made the transgenic rice were first introduced to cells of three Japonica rice varieties with the Biolistic particle delivery system, the "gene gun" invented at Cornell by plant biologist John Sanford and electrical engineer Edward Wolf. Cornell Research Foundation has applied for patents on the transgenic rice technologies.
Now that molecular biologists know how to transfer the insect-resistance gene to rice, Wu predicted, it should work against any lepidopteran (or caterpillar type) insect that eats plants in the larval stage -- and that is about 70 percent of the known insect pests worldwide. Among crops damaged by lepidopteran insects are sorghum, oats, rye, barley and wheat, as well as corn and rice.
In the case of the highly destructive rice pest, the pink stem borer, the insect enters the plant near the base and eats its way to the top of the stem where the rice grains form, either killing the plant or greatly reducing its yield. Because the transgenic plants do not produce an insect toxin -- just a proteinase inhibitor that disrupts insects' digestion -- the strategy is not 100 percent effective in eliminating insects, the Cornell scientists noted. Greater insect resistance can be easily achieved by adding genes that cause the plant to produce the Bt (Bacillus thuringiensis) toxin, Wu said.
Anticipating potential objections to the genetically engineered rice plants, Wu said that the potato proteinase inhibitor has no effect on humans, and it is present in raw the form of a related plant -- tomatoes. Nor are insects themselves likely to ever develop resistance to the proteinase inhibitor, as they eventually do to many toxins and chemical pesticides, because the protein has a different type of action on their systems, he said.
And genes for the insect-, salt- and drought-resistant rice should stay where the genetic engineers put them and not escape to produce a super weed, Wu said, because rice is a self-pollinating plant and few other plants can cross-pollinate with it.
The Rockefeller Foundation's Toenniessen observed that undernourishment already is a problem in most rice-dependent countries of Asia. "Populations are projected to continue growing for at least 30 years, and essentially no land is left for agricultural expansion," he said. "Discoveries such as those made at Cornell reduce crop losses and help farmers to produce more food on the same land while causing less environmental damage."