Engineered potatoes said to fight off fungus

WASHINGTON (Reuters) -- A borrowed alfalfa gene has helped potatoes fight off a fungus that causes one type of potato blight, researchers said this week.

They said it was the first time a single gene had been shown to protect a plant as well as herbicides do, and said they hoped they had found a way to use genetic engineering to protect against a range of diseases.

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The researchers, based at Monsanto, an 85 percent owned subsidiary of Pharmacia Corp., based their work on the highly successful use of another gene to protect against bugs.

Many crops are now engineered to produce Bacillus thuringiensis (Bt), which some plants make naturally to fight insects. But nothing has been found to work against fungi, which can devastate potatoes.

Potatoes, along with rice, wheat and corn, are one of the four major food crops of the world. Developing nations are turning to potatoes because they can be harvested in as little as 90 days.

One fungus, potato late blight, struck Ireland and continental Europe in the 1840s, causing at least a million people in Ireland to starve.

Late blight caused by the fungus Phytophthora infestans, costs potato growers about $3 billion a year, according to the International Potato Center in Lima, Peru. Another fungus causing early blight costs an estimated $21 million to $44 million to control in the United States and Canada alone.

Other crops such as alfalfa do not fall victim to these fungal diseases. Ai-Guo Gao and colleagues at Monsanto analyzed extracts from alfalfa and isolated a peptide they called alfAFP, for alfalfa antifungal peptide.

It belongs to a class of peptides called defensins and it has strong action against Verticillium dahliae, which causes "Verticillium wilt" or potato early dying complex.

They genetically engineered potatoes to produce alfAFP and planted them in soil infected with V. dahliae. The genetically modified potatoes survived well, they reported in the December issue of the journal Nature Biotechnology.

They have grown them in fields in Illinois, Wisconsin, and Oregon, which all have problems with fungal disease.

"There have been no previous demonstrations of a single transgene (transplanted gene) imparting ... disease resistance ... that is at least equivalent to those achieved through current practices using fumigants," the researchers wrote.

They also tried their new potatoes out against a fungus that causes early blight, but it did not work especially well, they reported.

More tests will have to be done to see how the transplanted gene affects the vitamin and mineral content, taste and yield of the potatoes, they said.

Monsanto has had a tough time with its genetic engineering of crops, such as its Round-Up Ready soybean that resists a weedkiller of the same name.

Biotech crops are popular with U.S. farmers because they offer higher yields. In Europe, activists have demonstrated against genetically engineered crops and some of the fears have transferred to U.S. consumers.

Huge news media attention has surrounded the recalls this year of 300 types of taco shells, chips and cornmeal made with StarLink corn, produced by Aventis SA. The genetically engineered corn has not been shown to cause any harm but is not approved for use in people.

Scientists with the Centers for Disease Control and Prevention in Atlanta, and the Food and Drug Administration have said they were investigating claims that at least 35 Americans became ill after eating foods containing StarLink corn. But federal officials said investigators may never be able to pinpoint whether the modified maize was to blame.

Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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Links to Web sites about potatoes
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