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WSU’s On Solid Ground – Citrus Greening, Superfruits, Goldwater – May 8, 2013

Posted by l.meyer | May 8, 2013

U.S. Orange Growers Feeling Squeezed

Citrus affected by citrus greening disease. (Photo courtesy of the U.S. Department of Agriculture)
Citrus greening prevents fruits from ripening and threatens the industry. Photo courtesy the U.S.D.A.

If left unaddressed, the entire U.S. citrus industry could be wiped out. In addition, as Florida Senator Bill Nelson said, “We’ll end up paying $5 for an orange-–and it’ll be one imported from someplace else.”A pandemic is destroying orange groves in Florida. The disease, called citrus greening, is also spreading to citrus groves in Texas and California, threatening an industry valued at more than $3 billion per year.

Citrus greening disease is spread by bacteria that block trees’ nutrient and water chann

els and prevent fruit from ripening. “It’s like choking the tree from the inside out,” said David Gang, a WSU molecular biologist and biochemist who is collaborating with a large, interdisciplinary team to combat the disease.

The Culprit

The bacteria are hosted and spread by an insect related to aphids and whiteflies called the Asian citrus psyllid (pronounced sill-id). The disease is thought to have spread from China in the early 2000s. Citrus greening has already destroyed the citrus industry in Jamaica.

The invasive psyllids pierce the citrus trees with a needle-like mouthpiece, similar to the way a malaria-transmitting mosquito infects its victims. As it feeds on the tree’s water and nutrients, the psyllid injects the disease-causing bacteria, which then spreads through the rest of the plant.

To combat this aggressive disease, the U.S. Department of Agriculture has funded a multifaceted, multi-institutional, multi-state initiative involving more than 40 researchers. These scientists are looking at the disease’s ecological consequences, the biology of citrus trees, the Asian citrus psyllid, and the mechanism(s) by which the insect transmits the greening disease bacteria.

Pesticides have been of some use in controlling the psyllids, but researchers are concerned the insects will develop resistance. And biocontrols-–siccing good bugs to prey on the bad ones-–have proven ineffective because the psyllids simply outbreed their predators.

That’s where David Gang enters the scene.

Altering the Insect

“Getting good quality data from this kind of approach is actually quite challenging,” Gang said. “But once you learn how to do it, the procedure is relatively routine; because of that, we were invited to be part of this project.”Gang’s lab in the WSU Institute of Biological Chemistry specializes in using new technologies like genomics and proteomics to study plant defense mechanisms, particularly the chemical compounds that help plants survive and combat pathogens and pests. In the USDA-funded project, Gang and his colleagues isolate and sequence the genes being expressed in the psyllids as they feed on citrus plants.

Once Gang and his colleagues obtain gene expression data, they make it available in a database for their collaborators to use. “We hope this data can be used to develop a “nupsyllid” (as in “new-psyllid”) that will be unable to transmit or harbor the citrus greening bacteria,” Gang said.

The researchers are also turning to genetic engineering as a last resort weapon against citrus greening: “We can shut off genes that are involved in transmission of the bacterium,” said Gang. Since citrus plants have no inherent defense and consumers reject genetically engineered food, the research team is focused on modifying the disease-transmitting pest. Gang said that nupsyllids are expected to outcompete and eventually replace the disease-spreading psyllids because citrus greening disease infects and weakens its insect host.

Avoiding Devastating Damage

Ensuring the economic and horticultural health and sustainability of the U.S. citrus industry is the goal of the USDA-funded five-year project. “The investment the USDA is putting into this project is really very small compared to the economic damage already caused by this disease and is trivial compared to the potential damage that could be caused down the road,” Gang said. “It’s one of those things where we don’t really have a choice. If we don’t do something, all of the citrus trees in the United States will likely be dead within 10-20 years.”

That’s why he and his colleagues are seeking a workable genetic solution to the citrus greening challenge, Gang said: “We’re kind of proud of the fact that it’s difficult to do and we’re good at it.”

Learn more about the work in David Gang’s lab at http://lcme.wsu.edu/people.php.

-Chelsea Pickett

Bringing Home Scotland Superfruit Study Findings

Raspberries are one of the "superfruits" being studied this summer by WSU Mount Vernon weed scientist Tim Miller and his colleagues in Scotland. Photo by Tim Miller, WSU.
Raspberries are one of the “superfruits” being studied this summer by WSU Mount Vernon weed scientist Tim Miller and his colleagues in Scotland. Photo by Tim Miller, WSU.

When WSU weed scientist Tim Miller first teamed up with fruit researchers in the United Kingdom last summer, he was hoping to learn how weeds affect the quality and nutritional value of raspberries. This May 14-23, he is traveling back to the James Hutton Institute in Invergowrie, Scotland, for a second year of berry trials to refine his findings leading toward the production of a higher-quality “superfruit” in the Pacific Northwest

Miller developed the series of trial projects in order to find out whether weeds–or the herbicides used to control them–produce berries with less of the vitamin C and other antioxidants and nutrients which make the fruit so healthful and appealing to consumers. His research complements that of UK researchers who have perfected the method for measuring the amounts of various compounds in raspberry and black currant, the two so-called superfruits which contain large amounts of antioxidants.When WSU weed scientist Tim Miller first teamed up with fruit researchers in the United Kingdom last summer, he was hoping to learn how weeds affect the quality and nutritional value of raspberries. This May 14-23, he is traveling back to the James Hutton Institute in Invergowrie, Scotland, for a second year of berry trials to refine his findings leading toward the production of a higher-quality “superfruit” in the Pacific Northwest.

Antioxidants are vitamins, minerals, and other nutrients that protect and repair cells from damage caused by free radicals that can impair the body’s immune system. Superfuits are believed to help fight off that damage by boosting the immune system, enabling the body to better ward off colds, flu, and other infections.

Collaborative Compatibility

“Since we both grow berries, it was a natural thing for a Pacific Northwest weed scientist and the small fruit breeders in the United Kingdom to team up and see what some of the factors are that affect berry quality,” said Miller. His initial Scottish berry trial results linked the presence of some hard-to-control weeds like broadleaf dock, fireweed, and quackgrass to such negative impacts on berries as lower amounts of sugar and vitamin C, as well as reduced color and sweetness. Miller hopes this year’s trials will provide even more useful information for berry growers and consumers across the globe. For raspberries, one common factor may be how weeds are managed. “Producers in the Pacific Northwest, as in Scotland, use herbicides to manage cane growth and control weeds,” Miller said. Their research may determine–for the first time–whether weed control also influences berry quality, sugar content, color, and antioxidant levels.

“A better understanding of the potential effects of management decisions will give growers one more tool to improve not only the yield of their fruit, but also how good that fruit is for consumers,” Miller said. “Whenever you test living plants in the real world, you can expect some variation in the results from year to year. If berry quality factors respond the same way two years in a row, it’s a good indication that you are looking at a true response rather than simply a short-term reaction to temperature or some other environmental factor.”

Read more about Tim Miller’s work with berries at http://bit.ly/130LZnE.

-Brian Clark and Cathy McKenzie

Developing a Plan to Feed Future Generations

Olympia native and WSU undergraduate Sarah Brewer describes herself as a “plant-aholic” who first got her hands dirty in a backyard greenhouse where she and her stepfather grew 16 varieties of tomatoes.

Sarah Brewer plans on researching cotton seed as a consumable.
Sarah Brewer plans on researching cotton seed as a consumable.

Brewer’s high school teacher helped ignite her interest in biology and inspired a curiosity for how plants work at a basic level. He also introduced her to Norman Lewis, WSU Regents Professor, professor of molecular plant sciences and chemistry, and director of the Institute of Biological Chemistry (IBC).

Funded by a National Science Foundation grant, Brewer was selected to be a high school intern in Lewis’ IBC lab the summer between her junior and senior years. She returned to the lab her first day on the WSU campus as a freshman and has been there ever since.

“Plants are important to food, medicine, and fibers, so there are many directions my work could go,” Brewer said. “It’s difficult to know how to make oneself most useful as a plant scientist. I think about societies facing food shortages and other challenges in coming years, plus how climate change is impacting the entire world. I think I’d like to create new cultivars of plants for the future that would be drought-resistant.”

Brewer is also looking into research that could lead to a new protein-rich human and animal consumable: cotton seed. While the seeds are 22% protein, some of the molecules in them are toxic to animals with a single-compartment stomach, such as humans or swine.

Brewer’s experimental strategy is to reveal how cotton plants produce gossypol, which is the problematic toxic compound that also has desirable qualities, including anticancer and plant pathogen defense mechanisms. She hopes to establish the biochemical and molecular reasons for these effects so the positive can be optimized and the negative eliminated. Conducted over the coming year, she will also use the project for her Honors College thesis.

Broad Focus

Now a junior, Brewer has two majors: one in agricultural biotechnology and another in biochemistry in the College of Veterinary Medicine. Ag biotech emphasizes the development and application of new technology to ensure a safe and abundant food and fiber supply. It aligns perfectly with Brewer’s career goals to earn a Ph.D. in plant biology, become a university professor who inspires undergraduates to pursue science careers, and conduct interdisciplinary research in molecular plant sciences.

Brewer recently received national awards from the Barry M. Goldwater Scholarship and Excellence in Education Program to support her quest to make the world a better place. She hopes to qualify next for a Marshall scholarship that would allow her to study in the United Kingdom. Learn more about the Goldwater Scholarship and Excellence in Education program at http://bit.ly/123U5vf.

-Beverly Makhani