Posts Tagged: walnuts
When consumers are asked in surveys whether they would buy genetically engineered (GE) produce such as fruit, most say they would not buy GE produce unless there were a direct benefit to them, such as greater nutritional value.
Yet with continuing invasions and spread of exotic insects and diseases for which there is no known control, the potential importance of trees or vines with some form of genetically engineered resistance is on the rise. In California, such diseases include Pierce's disease in grapes, crown gall disease in walnuts, and the invasive citrus greening (huanglongbing or HLB) in citrus.
"These are potentially devastating diseases to California growers, who produce 70 percent of the fresh fruit and nuts for the entire United States," notes Victor Haroldsen, scientific analyst at Morrison and Foerster, in the current California Agriculture. "They are also a mainstay of the California economy. Fruit and nut tree crops accounted for one-third of the state's total cash farm receipts, or $13.2 billion in 2010."
Now, however, Haroldsen reports that there may be a way to satisfy both consumers and growers — called "transgrafting."
"In transgrafting the genetically engineered rootstock can potentially confer the whole plant with resistance to disease. Yet the rootstock does not transfer the modified genes to the fruits or nuts produced," said Haroldsen.
Although over 10 years old, transgrafting technology is just now nearing commercialization, partly due to the long generation times of most trees and vines. Two such transgrafting applications are: a crown gall-resistant walnut rootstock, and a grape rootstock that confers moderate resistance to Pierce's disease.
"The key advantage of transgrafting is that the plant's vascular system can selectively transport across graft junctions the proteins, hormones, metabolites and vitamins from the roots without changing the heritable genes or DNA sequence in the fruit or nut." says Haroldsen.
In recent research at UC Davis, Haroldsen (a former graduate student) and his colleagues confirmed that modified DNA and full-length RNA from the rootstock does not cross the "graft union" into the scion, in the walnut and grape applications, or in a tomato model of these two systems.
"These current GE applications address root or xylem pests and diseases, but future applications will likely target traits aimed at consumer needs such as increased nutritional value or improved flavor," said Haroldsen. "If perceived risks to personal health and the environment could be reduced, genetic engineering could benefit not only growers but Californians around the state," he adds.
Consumer concerns about GE fruit are a factor discouraging commercialization. Plums shown are engineered to resist plum pox virus; they have received regulatory approval, but have not come to market.
Wild-type (left) and GE (right) walnut microshoots, after inoculation with crown gall-inducing virus. The wild-type shows tumor growth; the GE microshoot on the right does not. Transgrafting allows disease resistance to protect the plant while maintaining non-GE nuts.
Can what we eat help fix what ails us? Research increasingly suggests the answer is “yes.” Many foods contain biofactors — biologically active compounds — that may prevent and treat illnesses including asthma, diabetes and heart disease, according to new studies from the UC Davis Center for Health and Nutrition Research (CHNR).
The upcoming July-September California Agriculture journal (to be posted by July 11) reports UC research into plant compounds (phytochemicals) that can help prevent or treat disease. The findings stem from pilot projects at the center, as well as other UC research. Articles focus on how micronutrients, biofactors and phytochemicals (plant compounds) can help reduce the risk of chronic diseases.
Phytochemicals and health. Epidemiological studies link particular diets to less risk of chronic diseases. Notably, the traditional Mediterranean diet — mostly vegetables, fruits and whole grains, with moderate amounts of nuts, olive oil and red wine — is associated with lower rates of heart disease, cancer, and Parkinson's and Alzheimer's diseases. However, it has yet to be firmly established that specific phytochemicals in our diets can protect against diseases. Nutritionists therefore advise eating a wide variety of plant-based foods rather than taking supplements.
Mitochondrial nutrients and aging. The Mediterranean diet is rich in plant compounds that boost mitochondria (organelles in our cells that convert glucose and other nutrients into energy) and so are known as mitochondrial nutrients. When mitochondria are scarce or have genetic defects that keep them from working properly, this can generate toxic metabolites and damaging free radicals.
“Mitochondria are central to aging,” says UC Irvine aging expert Edward Sharman. “Improving their function may modulate or delay the onset of diseases related to aging, such as type 2 diabetes and age-related macular degeneration.” Mitochondrial dysfunction also plays a key role in chronic illnesses such as heart disease, type 2 diabetes and inflammatory diseases such as arthritis.
A new essential nutrient? Another promising mitochondrial nutrient is pyrroloquinoline quinone (PQQ), which was first found in nitrogen-fixing soil bacteria and is now known to be ubiquitous.
“We’re exposed to PQQ all the time at low levels,” says CHNR co-director Robert Rucker, a UC Davis nutrition professor. “It can be derived from amino acids found in stellar dust, and stellar dust is what the earth is made of.”
While Escherichia coli and other common gut bacteria do not make PQQ, the soil bacteria provide it to the plants in our diet. Good sources include fermented soybeans, wine, tea and cocoa.
Animal studies show that PQQ affects health markedly. Rucker and his colleagues found that depriving rats of PQQ compromised their immune systems, and retarded their growth and reproductive rates. In contrast, restoring PQQ to their diets reversed these effects and returned them to good health. Moreover, PQQ stimulated nerve growth and counteracted aging in cultured cells.
Rucker and his colleagues found that, like hydroxytyrosol, PQQ increases the number of mitochondria in cells. “It’s also an extremely good antioxidant and anti-inflammatory agent,” he says.
Personalized medicine. Understanding what biofactors do in our bodies could ultimately lead to personalized medicine, where nutrition-based treatments are tailored to the particulars of each person’s biochemistry. This individual variation at the biochemical level may help explain the inconsistent outcomes of research on omega-3 fatty acids and inflammation.
“The studies are mixed,” says UC Davis pulmonologist Nicolas Kenyon. “Some have shown little effect and others have shown that omega-3 fatty acids can reduce arthritis and inflammation in blood vessels.”
This genotyping is targeted to DNA sequences associated with asthma and so is not comprehensive.
“Some people are nervous about genome-wide analysis, which is scary because none of us is perfect,” Kenyon says. “But people are more interested when the focus is specific screening that could increase their chances of treatment.”
Two free publications on nuts have recently been published by ANR — Nuts: Safe Methods for Consumers to Handle, Store, and Enjoy and Nuts: Safe Methods for Home Gardeners to Harvest, Store, and Enjoy.
Both publications outline the nutritional benefits of eating nuts, including information from the FDA affirming that:
- Including nuts in a diet low in saturated fat and cholesterol may help reduce the risk of heart disease.
- Almonds, pecans, pistachios, and walnuts contribute to health through their protein, dietary fiber and unsaturated fat.
The consumer publication includes a handy table outlining optimal freezer and refrigerator storage times for a variety of nuts as well information on nut allergies, nutrition and resources for recipes.
Home gardeners with nut trees will find useful information on harvest times and methods, hulling and drying procedures, safe handling procedures, storage, and nutrition information for almonds, chestnuts, pecans, pistachios and walnuts.
Inside both publications is a discussion of recent bacterial outbreaks in nuts and the steps producers have taken to minimize the risk of exposure to consumers.