California Fruit and Vegetable

Tag: ARS

  • USDA Study Reveals Airborne Fungus Can Trigger Plant Growth

    The U.S. Department of Agriculture’s (USDA) Agricultural Research Service (ARS) recently announced that a harmless airborne fungus, Cladosporium sphaerospermum strain TC09 (TC09), can dramatically accelerate plant growth if a germinating plant is near the fungus as it emits volatiles or gases.

    Scientists used tobacco and pepper plants as models to study the conditions for accelerated plant growth once exposed to TC09. Following a relatively short duration of exposure at the seedling stage, the plants began to sense the fungi’s volatiles and gases. USDA scientists were then able to stimulate extremely rapid plant growth, earlier flowering and fruit yield increases.

    “This is a game-changer for agriculture and for research that seeks innovative ways to accelerate plant growth,” said USDA Scientist Dr. Chris Dardick. “Its implications are far-reaching and will help ARS’ commitment to deliver cutting-edge scientific advances for American farmers and producers.”

    The effects of TC09 were largely correlated with the duration of exposure. Visual observation indicated that plants with TC09 exposure for 10 days exhibited substantially more vigorous growth, thicker stems, larger leaves, and a more robust root system relative to plants without fungal exposure. Results also showed that treated plants flowered 20 days sooner and pepper plants yielded up to 213 percent more fruit that was ready for harvest three weeks earlier than untreated controls. More recent studies have shown similar research results for numerous other crops such as lettuce, arugula, kale, basil, and other leafy greens.

    This species of fungus is commonly found in indoor environments and is not known to cause disease in plants or any ailments in humans or animals. Also, unlike other microbial species that have been tested, the researchers showed that TC09 does not induce defense or stress responses in exposed plants. Scientists hope to identify the specific volatiles and gases that stimulate plant growth in future research.

    Research on microbial biostimulants that enhance plant growth has recently intensified because they provide an eco-friendly, cost-effective and sustainable strategy to benefit agriculture. USDA scientists will continue to study TC09 and seek practical strategies to apply it during commercial crop production, particularly for urban and indoor agricultural systems. They are awaiting approval of a patent and commercial evaluation license and partnered with NASA to apply this research technology to spaceflight conditions. This research was supported in part by grants from USDA-ARS, ARS’ Appalachian Fruit Research Lab, and the Oak Ridge Institute for Science and Education.

    The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in agricultural research results in $20 of economic impact.

  • Plant, Insect Viruses Work Together to Spread Disease

    In what may be a first for science, researchers with the Agricultural Research Service (ARS) have found an example of plant and insect viruses working together to increase their spread.

    Molecular biologist Michelle Heck, of the ARS Emerging Pests and Pathogens Research Lab in Ithaca, NY, scouts for aphids (Photo by Jennifer Wilson, Cornell University).

    Michelle Heck, an ARS research molecular biologist, was leading research into poleroviruses, a type of plant virus spread by aphids, when she and Cornell University graduate students Jenny Wilson and Patricia Pinheiro made the surprising discovery. Heck is in ARS’s Emerging Pests and Pathogens Research Unit at the Boyce Thompson Institute, on the campus of Cornell University, in Ithaca, NY.

    “Poleroviruses produce a molecule, called P Zero (P0), which dampens the aphid’s immune system,” Heck said. “When the aphid immune’s system is turned down, it allows an aphid virus called a densovirus to infect the insect at very high levels.”

    Densoviruses have a curious effect on aphids: Aphids usually develop wings when the weather begins to cool, but densoviruses can induce the insects to sprout wings. When poleroviruses and densoviruses interact in this way, it allows them to carry the polerovirus farther and faster.

    “We think this is the result of evolution,” Heck said. “Both the plant virus and the insect virus have evolved to manipulate the aphid. Our work shows they are in cahoots to promote virus spread, though possibly at the aphid’s expense.”

    The research is vital to crop producers because aphids transmit more than 100 different viruses to peaches, tomatoes, potatoes, apples, cotton, cabbage, corn, and other plants. In particular, the potato leafroll virus can reduce the worldwide potato yield by more than 50 percent, causing the loss of 20 million tons of crop each year. There is a new and emerging polerovirus infecting cotton, cotton leafroll dwarf virus, that Heck and her team are now studying.

    “Aphids are resistant to many commonly used insecticides, so chemical treatment is not effective in killing them and blocking the spread of viruses,” Heck said. “By the time a farmer notices aphids in the field, it is too late to block the spread of these viruses by aphids.”

    Follow-on research includes a quest to understand how the polerovirus protein, P0, suppresses the aphid’s immune system at the molecular level. Heck is also looking at exactly how the densovirus triggers the aphid to grow wings.

    “We now know that poleroviruses can interfere with the aphid’s immune response to densoviruses,” she said. The question Heck hopes to answer is, can the densovirus infection be made so severe that it kills the aphids, and if so, could it be used as a biological control tool? – By Scott Elliott, ARS Office of Communications

  • Freeze-Dried Strawberries & Ice Cream Make for a Very Stable Relationship

    ARS researchers have shown some freeze-dried berry powders—especially freeze-dried strawberry powder—can act as outstanding stabilizers in ice cream and other frozen dairy desserts.

    Freeze-dried strawberry powder is so effective a stabilizer that frozen dairy desserts with it included will maintain their shape even after reaching room temperature, according to Agricultural Research Service (ARS) research food technologist Cristina Bilbao-Sainz with the Healthy Processed Foods Research Unit in Albany, California.

    To be technically classified as ice cream, it must contain between 10 percent and 16 percent milkfat; everything else is called a frozen dairy dessert.

    Physical scientist Craig Carriere enjoys fat-free soft-serve ice cream produced with Fantesk (Photo by Keith Weller).

    Without a stabilizer, ice cream—home-made or commercial—can become unpleasantly crunchy with the growth of large ice crystals. It can happen in either or both the ice cream maker or the freezer, when temperatures change. Stabilizers also slow down melting, prevent wheying off (the leaking of a clear watery serum), help avoid shrinking during storage and increase your mouth’s perception of creaminess.

    Standard stabilizers such as sodium alginate, guar gum, iota carrageenan, xanthan gum and carboxymethyl cellulose are commonplace. But people tend to react negatively to these unfamiliar, chemical sounding names when they appear on an ice cream label, assuming these must be artificial ingredients.

    Actually, many do come from natural sources. For example, sodium alginate is extracted from brown seaweed.

    Bilbao-Sainz became intrigued with the idea of freeze-dried fruit powders as ice cream stabilizers when an all-natural dessert maker came looking for scientific facts about them. The possibilities of freeze-dried fruit powder have been previously known but not technically quantified.

    “We discovered that some of the freeze-dried fruit powders—especially strawberries—completely prevent the melt-down of dairy frozen desserts similar to ice cream made with whole milk, whole whipping cream, sugar and skim milk powder,” Bilbao-Sainz said. “Freeze-dried berry powder will absorb moisture from the premix base, improving its stability and texture to the point where the frozen dessert will keep its shape even after “melting” to room temperature.”

    This is probably due to the fiber in the berry powder becoming completely hydrated, which contributes to an increase in viscosity and resistance to melt-down, she explained.

    In Bilbao-Sainz’s testing, adding 3.5 percent of either strawberry, raspberry or blackberry freeze‐dried powder reduced the water available for ice crystal formation during stirring and freezing, preventing crystal growth and slowing melting. That translates to adding about 0.7 ounces for a 1-quart home ice cream maker.

    Strawberry powder was the best stabilizer, completely preventing melt‐down, followed closely by raspberry. While blackberry powder prevented the frozen dessert from wheying off the foam structure still collapsed so it lost its original shape.

    Blueberry powder, on the other hand, did not prevent melt-down or ice crystal formation during refreezing, and the frozen dessert showed a little wheying off.

    Of course, using freeze-dried strawberry powder as a stabilizer in frozen dairy desserts such as ice creams also means accounting for the added strawberry flavoring—a plus if you are making strawberry balsamic vinegar ice cream, more difficult in a brown butter bourbon ice cream recipe. — By Kim Kaplan, USDA-ARS

    This research was published in the Journal of Food Processing and Preservation. The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in agricultural research results in $20 of economic impact.

  • New Traps Cut Off Citrus Greening Pests from Hiding Places

    Researchers across the nation are struggling to end the scourge of citrus greening disease, also known as huanglongbing. The disease renders citrus fruit inedible and eventually kills entire orchards. In Florida alone, from 2012-2016 the disease caused production losses of $4.4 billion and eliminated about 7,900 jobs.

    With economic impact like that, it’s no wonder that previous citrus greening research and mitigation efforts have mainly focused on commercial production. Now, researchers with the Agricultural Research Service’s (ARS) Horticultural Research Laboratory in Fort Pierce, FL, and their collaborators are bringing the citrus greening fight to the suburbs, where citrus trees are popular landscape plantings.

    The Asian citrus psyllid, an insect about the size of an aphid (roughly 1/8 of an inch), carries the bacterium Candidatus Liberibacter asiaticus in its salivary glands. As it feeds on citrus leaves, the psyllid transmits the bacterium to the tree. The bacterium then prevents sugars created through photosynthesis from traveling throughout the tree. The result is yellowed leaves, bitter fruit, and eventual tree death.

    Spraying insecticides is not really an option in residential areas because many homeowners either have concerns about insecticides or find it too difficult to adequately treat backyard trees, said ARS research entomologist Joseph Patt.

    “There are virtually no control measures being taken against psyllids in citrus trees growing in residential and commercial landscapes,” he said. “This is important because the psyllid can fly from residential areas to commercial citrus groves. In other words, residential areas provide a kind of refuge for the psyllids because homeowners haven’t had a way to control them in their backyard trees.”

    Leaves of an orange tree infected with Huanglongbing, or citrus greening. The blotchy mottling pattern seen here, along with thickening, are characteristic symptoms of infected leaves.

    Patt and Texas A&M-Kingsville entomologists Andrew Chow and Mamoudou Setamou developed “attract-and-kill” traps to prevent this hide-and-seek, back-and-forth migration of psyllids. The traps, which are hung from citrus trees, are the same color as young citrus foliage and contain a fast-acting insecticide that kills the psyllid. According to Patt, the traps provide an environmentally friendly way for homeowners to help control Asian citrus psyllid and citrus greening disease. The insecticide remains in the device and does not spread to the surrounding foliage. The active ingredient is not toxic to mammals or birds and does not persist in the environment.

    Initial testing was completed last year in the Rio Grande region of Texas. “The results are promising,” Patt said. “Deployment of 20 attract-and-kill devices per test tree resulted in a 90-percent decrease in psyllid eggs compared to unprotected test trees. We are currently working on a design for use in commercial citrus. Psyllids invade citrus groves by first landing in the trees growing along the edge of the grove, so we will run tests to determine if devices placed only on border trees are effective in controlling the psyllid throughout the grove.” – by Scott Elliott, USDA-ARS Office of Communications