Transgenic peanut varieties perform well in trials

Peanut production in Virginia is up in 2007 and the future looks even more optimistic as researchers at Virginia Tech University inch closer to getting transgenic versions of two popular varieties (Wilson and Perry) ready for growers.

The end result will be elimination of one of the biggest obstacles to growing peanuts in North Carolina and Virginia — sclerotinia blight.

Researchers added barley oxidase oxalate genes to Wilson, Perry and NC-7 peanuts and have grown these peanuts from the lab to the field for seven growing seasons with the often called ‘boo’ genes carrying over flawlessly from one generation to the next.

In highly regulated tests, yield and quality components are almost identical to non-transgenic peanuts from the same two varieties. The only difference is the transgenic peanuts have a very high level of resistance to sclerotinia blight.

Even NC-7, which is notorious for its susceptibility to the disease, has shown virtually no infection, when the boo gene is included in its genetic makeup.

Virginia Tech researchers Pat Phipps and Beth Grabau are heading a team of scientists determined to provide Virginia growers with these genetically improved varieties that will allow them to overcome devastating yield losses and economically debilitating costs of controlling sclerotinia blight.

Phipps, a plant pathologist at the Tidewater Area Research and Education Center in Holland, Va, with over 25 years experience with peanut diseases and Grabau, a plant physiologist with a keen interest in genetics, based on the Virginia Tech campus at Blacksburg, have been working on genetically improved peanut varieties for seven growing seasons, including 2007.

Though the wheels of government regulation turn slowly, sometimes incredulously slow, in the case of the transgenic peanuts, they are turning. “Nobody has ever developed genetic disease resistance in peanut varieties, and we have been a kind of model case for the regulatory agencies,” Phipps says.

Far from blaming regulatory agencies for the long-term development of the sclerotinia blight resistant varieties, Phipps explains that errors on the side of caution are much preferable to rushing into genetic changes that may damage the environment. “We will present our data this winter to APHIS, the regulatory agency for transgenic crops, in hopes of getting these varieties deregulated. If that happens we can get the transgenics into variety tests across the region and begin the process of getting them ready for growers,” Phipps says, admitting that is still a good ways down the road.

From the technical perspective, the transgenic peanut varieties have performed flawlessly. The Virginia researchers isolated the barley oxalate oxidase gene that creates an enzyme that breaks down oxilic acid, which the causal agent for sclerotinia blight must have in order to create infection in a peanut plant.

Technically, what happens inside the transgenic plants is oxalate oxidase (OXO) converts oxalic acid (OA) and O2 to CO2 and hydrogen peroxide (H2O2), and acts as a source of H2O2 in certain plant-pathogen interactions.

The fungus that causes sclerotinia blight must have oxalic acid when it contacts peanut plants to cause an infection. The boo gene essentially robs the fungus of its ability to cause disease.

So far, seven generations of Wilson, Perry and NC-7 peanuts that carry the boo gene have performed in every way as well as their parent, except they have resistance to sclerotinia blight. “We have seen no resistance to CBR or leafspot, or any other difference in the transgenic varieties, other than sclerotinia resistance,” Phipps stresses.

Even aflatoxin levels are within 1 to 2 parts per billion the same for transgenic versus non-transgenic plants from the same variety. Again, it would be nice if aflatoxin could be eliminated all together, but the boo gene doesn’t have that capability. Fortunately Virginia type peanuts are not usually as susceptible to aflatoxin problems as runner varieties.

While growers would like to see additional disease resistance, from a research standpoint and from an envirionmental safety standpoint, the boo gene is doing exactly what it is supposed to do and nothing else — a big strongpoint for regulatory purposes.

Pod size, shape and brightness in Wilson peanuts, for example, with the boo gene is identical to those agronomic characteristics in Wilson peanuts without the boo gene. Even the fatty acid levels, and other mineral and nutrient levels in transgenic and non-transgenic are the same, according to Phipps.

Out-crossing of the gene from one row to the next is very low. And, as it goes further away from the row, out-crossing tends to go away completely. Even from one row to the next is only 1-2 percent. For safety purposes, transgenics are separated by at least a quarter of a mile. Peanuts are self-pollinating, so out-crossing is not likely to be a problem. All in all the transgenic peanuts are about as stable as a crop can be, making it more reasonable to expect fairly quick acceptance of the data package for deregulation.

The Virginia Tech scientist, who has been an ardent supporter of peanut growers in Virginia throughout his career, is optimistic that getting a transgenic variety onto the market will greatly speed the process along for development of future peanut varieties with resistance to other disease problems.

Sclerotinia blight was first detected in Virginia in 1971. Since that time it has spread to North Carolina and in more recent years has become a serious economic threat to peanuts in Texas and Oklahoma. Disease losses, especially in the cooler regions of North Carolina and Virginia, can be catastrophic, commonly exceeding 50 percent.

Though several management strategies have been developed for the disease, the common united thread is cost. The high cost of managing sclerotinia, and to a lesser degree other diseases, has consistently driven peanut acreage down in Virginia and parts of North Carolina.

For most of his career Phipps has helped Virginia peanut growers battle sclerotinia blight. He is dogged in his determination to get these new transgenic varieties to growers. And, he hopes to provide an open path for other researchers to develop other varieties with resistance to other common diseases of peanuts.

Phipps hopes the new transgenic variety will be released as a Virginia Tech variety. “In the case of Perry, which is a good variety with CBR resistance and other good production traits, we would include North Carolina State in the release, because the parent belongs to them.

“Beth Grabau and I are very interested in getting these varieties to growers as soon as we can. It has been a long process, but one that hopefully will pay off for peanut growers,” Phipps says.

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