Pubdate: Tue, 20 May 2003 Source: Newsday (NY) Copyright: 2003 Newsday Inc. Contact: http://www.newsday.com/ Details: http://www.mapinc.org/media/308 Author: Robert Cooke, Staff Writer SOUPED-UP FUNGI AIMED AT WEEDS Researchers Find Early Success With Genetic Engineering By engineering new genes into plant-killing fungi, scientists in Israel report they're creating extra-potent biological weed-whackers. The fungi, which can be applied via spraying, are still in the research phase. Before being widely used, said plant scientist Jonathan Gressel, the gene-modified fungi must be guaranteed safe. But if super-efficient weed-killing fungi do work and prove harmless, they could greatly improve farmers' ability to control weeds. Success should reduce food costs, energy use and herbicide application. "Weeds are the main pest restraint on row-crop agriculture," Gressel and his colleagues, Ziva Amsellem and Barry Cohen, wrote in Nature Biotechnology. In fact, "the major variable is control of weeds, whether mechanically or chemically." The researchers work at the Weizmann Institute of Science, in Israel. Digging weeds up can lead to erosion and damage to crop plants' roots. But herbicides create another set of environmental problems, such as runoff into water supplies and killing nearby plants accidentally, as well as weeds developing resistance to herbicides. The souped-up fungi might alleviate such problems with crops as varied as rice in paddies and the vast fields of vegetables that are grown in rows. Annually, farmers worldwide spend millions of dollars struggling to control weeds. In fact, said Gressel, "more than 60 percent of pesticides used in the developed world are herbicides for weed control." The problems posed by weeds are so costly and hard to solve that experts have tried to recruit insects, fungi and other naturally occurring plant-killing agents that might do the job easier, better or cheaper. Specific organisms such as fungi have been identified that naturally attack many of the most troublesome weeds. According to Gressel, attempts to use natural fungi have provided "a modicum of control" when the fungi are densely applied. But so far fungi "have not been sufficiently cost-effective" despite years of research and "have not met expectations." One reason for less-than-stellar success is that the fungi and the weeds tend to develop an evolutionary balance that allows both to survive, "even when the myco-herbicide [fungus] is used at very high levels." Application of fungi has also been difficult. For best results humidity has to remain at almost 100 percent for six to 18 hours after fungi have been applied. Gressel and his two co-workers tried engineering the fungal cells to improve performance. One step was to insert extra "virulence" genes into one strain of the fungus, Colletotrichum coccodes. The idea was to make the fungus kill weeds quicker and to make it effective on mature weeds as well as seedlings or juvenile plants. Also, the researchers want to keep the fungi from spreading beyond their target, so they're removing the genes responsible for sporulation, which is the production of tiny, seed-like spores. This tactic should stop spore production, or at least disarm the spores. The Israeli team also showed that adding special new genes made the fungus much more effective at killing the correct species. And, they said, the killing effect was extended over a longer period of time, allowing them to catch weeds that sprouted later. Eventually, highly specialized fungi might be targeted at plants such as opium poppies, cocaine and marijuana. This could even open a new "front" in the drug war. - --- MAP posted-by: Richard Lake