Friday, October 31, 2014
YOLO COUNTY NEWS
99 CENTS

Nutritionist finds clues to saving citrus from dreaded disease

By
From page A9 | March 10, 2013 |

UC Davis nutrition expert Carolyn Slupsky shows off a lemon tree as she explains research done by her team to find effective ways to treat and prevent the spread of citrus greening disease, also known as huanglongbing or HLB. Some Florida producers are masking the bitter taste of HLB-infected fruit in orange juice by giving consumers what is essentially sugar water. Courtesy photo

By Diane Nelson

A nutrition expert at UC Davis has discovered important clues to the deadly attack strategy of a puzzling plant pathogen that has destroyed hundreds of thousands acres of citrus across the world.

The novel research by Carolyn Slupsky, associate professor and nutritionist with the UCD department of food science and technology and Agricultural Experiment Station, and her team may pave the way for safe, effective ways to treat and prevent the spread of citrus greening disease, also known as huanglongbing or HLB.

“HLB is not just bad for growers and for the economy,” Slupsky said. “The loss of fresh oranges and other citrus could seriously impact our health.”

HLB is a disease caused by a microbe called Candidatus Liberibacter asiaticus and spread by the Asian citrus psyllid, a tiny insect that feeds on the leaves and stems of citrus trees. There is no cure yet for HLB, so once a tree is infected, it will slowly die. The disease has decimated citrus groves in Asia, Brazil and the Dominican Republic. Florida has lost one-third of its citrus to the disease. Both HLB and the Asian citrus psyllid have recently been spotted in California.

HLB is a silent killer — an infected tree can live for years without symptoms, allowing the pathogen to spread undetected to other trees. Symptoms emerge over time, as a tree’s fruit starts to turn green and misshapen, with a bitter, metallic taste.

Is there a way to spot HLB before visual symptoms occur? The microbe that causes HLB can sometimes be found in a leaf sample, but since the pathogen isn’t evenly distributed throughout the tree, results can be misleading.

“Just because the pathogen doesn’t show up in one leaf, that doesn’t guarantee the tree isn’t infected,” said MaryLou Polek, vice president of science and technology for the California Citrus Research Board. “So when you sample a leaf, there’s a high probability of a false negative result.”

Slupsky and Andrew Breksa, a research chemist with the USDA Agricultural Research Service based in Albany, tried a different tack, searching for clues in a tree’s chemical fingerprint. They used nuclear magnetic resonance spectroscopy to study the amino acid composition of juice from three types of citrus: fruit from healthy tress, symptom-free (asymptomatic) fruit from HLB-positive trees, and fruit with symptoms from HLB-positive trees.

“We found major differences in the chemical fingerprint among healthy, asymptomatic and symptomatic fruits,” Slupsky said.

With further research, the profiles may prove to be a reliable, rapid, and early indicator of the presence of the HLB pathogen. With early detection, growers and regulators can know which trees might need to be removed before the disease spreads throughout the orchard (and beyond).

“These findings are huge for citrus growers, backyard gardeners and everyone who loves fresh citrus,” Polek said.

And there’s more. While analyzing the amino acids, Slupsky and Breksa discovered what looks like a mechanism underlying the microbe’s mode of attack.

“The pathogen responsible for HLB seems to cause havoc with a tree’s ability to defend itself from infection,” Slupsky said.

Trees need amino acids for growth, development and defense. From Slupsky and Breksa’s studies, it looks like the HLB pathogen affects the trees’ ability to create, use and recycle some of those amino acids. For example, a tree can convert the amino acid phenylalanine into cinnamic acid, a precursor to compounds important to the tree’s defense systems. But juice from oranges of HLB-positive trees had significantly higher concentrations of phenylalanine.

Also, juice from oranges grown on HLB-infected trees contained a lot less of the amino acid proline, which a tree usually synthesizes when it knows something is wrong.

“It could be that the pathogen is outsmarting the tree by undermining its defenses,” Slupsky said. “That’s a spectacular discovery, because when we understand the mechanisms behind the attack, we have a chance at blocking them. Maybe we can find ways to enhance a tree’s natural immunity.”

As tough as HLB has been on citrus in Florida, the stakes are even higher in California where so much of the world’s fresh citrus is produced.

“Florida’s citrus industry produces mostly orange juice, and they can use additives and filtration to adjust for the bitter taste of HLB-affected fruit,” Polek said. “It can be reduced to sugar water, essentially, and then built back up to taste like orange juice. We produce fresh citrus here in California, and chemistry is not an option.”

Losing fresh citrus is a real possibility if HLB spreads throughout California, and that prospect is the driving force behind Slupsky’s research.

“From a nutritional standpoint, it’s hard to beat the importance of fresh citrus,” Slupsky said. “Oranges provide energy, pectin, and a wide variety of nutrients, vitamins and minerals. They’re one of the most consumed fruits in the United States. I can’t imagine life without fresh citrus.”

Slupsky and Breksa collaborated with Thomas G. McCollum of the ARS Horticultural Research Laboratory in Fort Pierce, Florida, along with Anne Slisz and Darya Mishchuk of Slupsky’s lab. A peer-reviewed article on their findings was published in the Journal of Proteome Research in June 2012.

— UC Davis College of Agricultural and Environmental Sciences

Comments

comments

Special to The Enterprise

.

News

 
State superintendent makes campaign stop in Davis

By Jeff Hudson | From Page: A1 | Gallery

State races test one-party rule

By New York Times News Service | From Page: A2

 
Couple killed in Yolo County crash

By Lauren Keene | From Page: A2

 
Same-party races challenge incumbents

By The Associated Press | From Page: A2

 
Indians celebrate Diwali with gala on Sunday

By Special to The Enterprise | From Page: A3

Rairdan dinged for late report

By Jeff Hudson | From Page: A3

 
Veterans will tailgate at ‘Salute to Heroes’ game

By Enterprise staff | From Page: A3

Wolk hailed for environmental votes

By Enterprise staff | From Page: A3

 
Yamada honored for leadership on aging issues

By Enterprise staff | From Page: A3

Embroidery group meets at mall

By Enterprise staff | From Page: A3

 
Bones for Life classes offered

By Enterprise staff | From Page: A4

Bet Haverim will hear Israel update

By Special to The Enterprise | From Page: A4

 
Local artisans featured at holiday craft fair

By Enterprise staff | From Page: A4

Got bikes? Donate ‘em!

By Enterprise staff | From Page: A4

 
Kids walk for friends at Birch Lane

By Special to The Enterprise | From Page: A4

Explorit: Creep out with some spooky science

By Lisa Justice | From Page: A4

 
Shambhala offers Tai Chi class

By Special to The Enterprise | From Page: A4

Enjoy wine, music and art at Sunday fundraiser for DHS choir

By Anne Ternus-Bellamy | From Page: A9

 
.

Forum

New-school cheating on the smartphone

By Creators Syndicate | From Page: B5

 
My choices on Tuesday

By Letters to the Editor | From Page: A10

 
Garamendi, Dodd get my votes

By Letters to the Editor | From Page: A10

Tom Meyer cartoon

By Debbie Davis | From Page: A10

 
High hopes for Sunder

By Letters to the Editor | From Page: A10

Public service is in her heart

By Letters to the Editor | From Page: A10

 
A calm, thoughtful voice

By Letters to the Editor | From Page: A10

Sunder is a perfect fit

By Letters to the Editor | From Page: A10

 
Best predictor is past behavior

By Letters to the Editor | From Page: A10

Vote for students, with Tuck

By Letters to the Editor | From Page: A10

 
.

Sports

DHS plays undefeated Pacers Friday night

By Enterprise staff | From Page: B1

 
Blue Devil girls net an easy win at Grant

By Enterprise staff | From Page: B1 | Gallery

Aggie offense A-OK; now what about defense?

By Bruce Gallaudet | From Page: B1 | Gallery

 
In Davis, rugby is as American as apple pie

By Bruce Gallaudet | From Page: B1

 
 
Niemi’s 43 saves aren’t enough in loss to Wild

By The Associated Press | From Page: B8 | Gallery

.

Features

.

Arts

 
Calling all artists for upcoming show

By Enterprise staff | From Page: A11

‘Birdman': A dark comedy that soars

By Derrick Bang | From Page: A11

 
DHS Madrigals host singing workshop

By Enterprise staff | From Page: A12

 
Marcia Ball to play at The Palms

By Enterprise staff | From Page: A12 | Gallery

 
.

Business

Big, capable luxury defines Yukon

By Ann M. Job | From Page: A5 | Gallery

 
.

Obituaries

Joseph Francis Gray

By Special to The Enterprise | From Page: A4

 
.

Comics

Comics: Friday, October 31, 2014

By Creator | From Page: B6

 
.

Real Estate Review

Featured Listing

By Special to The Enterprise | From Page: RER1

Professional Services Directory

By Special to The Enterprise | From Page: RER2

Lyon Real Estate

By Special to The Enterprise | From Page: RER3

RE/Max Gold

By Special to The Enterprise | From Page: RER4

Kim Eichorn

By Special to The Enterprise | From Page: RER5

Yolo FCU

By Special to The Enterprise | From Page: RER6

Juan Ramirez

By Special to The Enterprise | From Page: RER6

Susan von Geldern

By Special to The Enterprise | From Page: RER6

Team Traverso

By Special to The Enterprise | From Page: RER6

Tracy Harris

By Special to The Enterprise | From Page: RER7

Susan von Geldern

By Special to The Enterprise | From Page: RER7

Wells Fargo Home Mortgage

By Special to The Enterprise | From Page: RER8

Julie Leonard

By Special to The Enterprise | From Page: RER8

Joe Kaplan

By Special to The Enterprise | From Page: RER9

Melrina A Maggiora

By Special to The Enterprise | From Page: RER9

Coldwell Banker

By Special to The Enterprise | From Page: RER10

Leslie Blevins

By Special to The Enterprise | From Page: RER12

Julie Partain

By Special to The Enterprise | From Page: RER12

Robin Garland

By Special to The Enterprise | From Page: RER13

Jamie Madison

By Special to The Enterprise | From Page: RER13

Diane Lardelli

By Special to The Enterprise | From Page: RER13

Karen Waggoner

By Special to The Enterprise | From Page: RER14

Jamie Madison & Associates

By Special to The Enterprise | From Page: RER14

Lisa Haass

By Special to The Enterprise | From Page: RER14

Ciana Wallace

By Special to The Enterprise | From Page: RER15

Travis Credit Union

By Special to The Enterprise | From Page: RER16

Malek Baroody

By Special to The Enterprise | From Page: RER17

Marcelo Campos

By Special to The Enterprise | From Page: RER18

F1rst Street Real Estate

By Special to The Enterprise | From Page: RER20