A Race to Save the Orange by Altering Its DNA
Trees that are infected by disease are cut down and burned in Clewiston, Fla., at groves owned by Southern Gardens Citrus. Richard Perry/The New York Times
By AMY HARMON
July 27, 2013 761 Comments
CLEWISTON, Fla. — The call Ricke Kress and every other citrus grower in Florida dreaded came while he was driving.
“It’s here” was all his grove manager needed to say to force him over to the side of the road.
The disease that sours oranges and leaves them half green, already
ravaging citrus crops across the world, had reached the state’s storied
groves. Mr. Kress, the president of Southern Gardens Citrus, in charge
of two and a half million orange trees and a factory that squeezes juice
for Tropicana and Florida’s Natural, sat in silence for several long
moments.
“O.K.,” he said finally on that fall day in 2005, “let’s make a plan.”
In the years that followed, he and the 8,000 other Florida growers who
supply most of the nation’s orange juice poured everything they had into
fighting the disease they call citrus greening.
To slow the spread of the bacterium that causes the scourge, they
chopped down hundreds of thousands of infected trees and sprayed an
expanding array of pesticides on the winged insect that carries it. But the contagion could not be contained.
They scoured Central Florida’s half-million acres of emerald groves and
sent search parties around the world to find a naturally immune tree
that could serve as a new progenitor for a crop that has thrived in the
state since its arrival, it is said, with Ponce de León. But such a tree
did not exist.
An orange from a tree infected with citrus greening, right, is stunted compared with a normal orange. Richard Perry/The New York Times
“In all of cultivated citrus, there is no evidence of immunity,” the
plant pathologist heading a National Research Council task force on the
disease said.
In all of citrus, but perhaps not in all of nature. With a precipitous
decline in Florida’s harvest predicted within the decade, the only
chance left to save it, Mr. Kress believed, was one that his industry
and others had long avoided for fear of consumer rejection. They would
have to alter the orange’s DNA — with a gene from a different species.
Oranges are not the only crop that might benefit from genetically
engineered resistance to diseases for which standard treatments have
proven elusive. And advocates of the technology say it could also help
provide food for a fast-growing population on a warming planet by
endowing crops with more nutrients, or the ability to thrive in drought,
or to resist pests. Leading scientific organizations have concluded
that shuttling DNA between species carries no intrinsic risk to human health or the environment, and that such alterations can be reliably tested.
I
invite you to share your perspective on the issues raised in my
article. What are the main considerations that inform your opinion on
genetically modified foods? — Amy Harmon, ReporterJoin the Discussion
But the idea of eating plants and animals whose DNA has been manipulated
in a laboratory — called genetically modified organisms, or G.M.O.’s —
still spooks many people. Critics worry that such crops carry risks not
yet detected, and distrust the big agrochemical companies that have
produced the few in wide use. And hostility toward the technology, long
ingrained in Europe, has deepened recently among Americans as organic
food advocates, environmentalists and others have made opposition to it a
pillar of a growing movement for healthier and ethical food choices.
Mr. Kress’s boss worried about damaging the image of juice long promoted as “100 percent natural.”
“Do we really want to do this?” he demanded in a 2008 meeting at the
company’s headquarters on the northern rim of the Everglades.
Mr. Kress, now 61, had no particular predilection for biotechnology.
Known for working long hours, he rose through the ranks at fruit and
juice companies like Welch’s and Seneca Foods. On moving here for the
Southern Gardens job, just a few weeks before citrus greening was
detected, he had assumed his biggest headache would be competition from
flavored waters, or persuading his wife to tolerate Florida’s humidity.
But the dwindling harvest that could mean the idling of his juice
processing plant would also have consequences beyond any one company’s
bottom line. Florida is the second-largest producer of orange juice in
the world, behind Brazil. Its $9 billion citrus industry contributes
76,000 jobs to the state that hosts the Orange Bowl. Southern Gardens, a
subsidiary of U.S. Sugar, was one of the few companies in the industry
with the wherewithal to finance the development of a “transgenic” tree,
which could take a decade and cost as much as $20 million.
An emerging scientific consensus held that genetic engineering would be
required to defeat citrus greening. “People are either going to drink
transgenic orange juice or they’re going to drink apple juice,” one
University of Florida scientist told Mr. Kress.
And if the presence of a new gene in citrus trees prevented juice from
becoming scarcer and more expensive, Mr. Kress believed, the American
public would embrace it. “The consumer will support us if it’s the only
way,” Mr. Kress assured his boss.
Workers inspected orange trees and marked the infected ones. Citrus greening has turned up in millions of trees. Richard Perry/The New York Times
Readers’ Perspectives
“While the notion of modifying
nature's bounty conjures up images of science run amok in the interests
of corporate interests, I see no principled difference between this and
stem cell research, with its aim to ameliorate human suffering.”
His quest to save the orange offers a close look at the daunting process
of genetically modifying one well-loved organism — on a deadline. In
the past several years, out of public view, he has considered DNA donors
from all over the tree of life, including two vegetables, a virus and,
briefly, a pig. A synthetic gene, manufactured in the laboratory, also
emerged as a contender.
Trial trees that withstood the disease in his greenhouse later succumbed
in the field. Concerns about public perception and potential delays in
regulatory scrutiny put a damper on some promising leads. But intent on
his mission, Mr. Kress shrugged off signs that national campaigns
against genetically modified food were gaining traction.
Only in recent months has he begun to face the full magnitude of the gap
between what science can achieve and what society might accept.
Millenniums of Intervention
Even in the heyday of frozen concentrate, the popularity of orange juice
rested largely on its image as the ultimate natural beverage,
fresh-squeezed from a primordial fruit. But the reality is that human
intervention has modified the orange for millenniums, as it has almost
everything people eat.
Before humans were involved, corn was a wild grass, tomatoes were tiny,
carrots were only rarely orange and dairy cows produced little milk. The
orange, for its part, might never have existed had human migration not
brought together the grapefruit-size pomelo from the tropics and the
diminutive mandarin from a temperate zone thousands of years ago in
China. And it would not have become the most widely planted fruit tree
had human traders not carried it across the globe.
The varieties that have survived, among the many that have since arisen
through natural mutation, are the product of human selection, with
nearly all of Florida’s juice a blend of just two: the Hamlin, whose
unremarkable taste and pale color are offset by its prolific yield in
the early season, and the dark, flavorful, late-season Valencia.
Because oranges themselves are hybrids and most seeds are clones of the
mother, new varieties cannot easily be produced by crossbreeding —
unlike, say, apples, which breeders have remixed into favorites like
Fuji and Gala. But the vast majority of oranges in commercial groves are
the product of a type of genetic merging that predates the Romans, in
which a slender shoot of a favored fruit variety is grafted onto the
sturdier roots of other species: lemon, for instance, or sour orange.
And a seedless midseason orange recently adopted by Florida growers
emerged after breeders bombarded a seedy variety with radiation to
disrupt its DNA, a technique for accelerating evolution that has yielded
new varieties in dozens of crops, including barley and rice.
Its proponents argue that genetic engineering is one in a continuum of
ways humans shape food crops, each of which carries risks: even
conventional crossbreeding has occasionally produced toxic varieties of
some vegetables. Because making a G.M.O. typically involves adding one
or a few genes, each containing instructions for a protein whose
function is known, they argue, it is more predictable than traditional
methods that involve randomly mixing or mutating many genes of unknown
function.
But because it also usually involves taking DNA from the species where
it evolved and putting it in another to which it may be only distantly
related — or turning off genes already present — critics of the
technology say it represents a new and potentially more hazardous degree
of tinkering whose risks are not yet fully understood.
If he had had more time, Mr. Kress could have waited for the orange to
naturally evolve resistance to the bacteria known as C. liberibacter
asiaticus. That could happen tomorrow. Or it could take years, or many
decades. Or the orange in Florida could disappear first.
Plunging Ahead
Early discussions among other citrus growers about what kind of disease
research they should collectively support did little to reassure Mr.
Kress about his own genetic engineering project.
“The public will never drink G.M.O. orange juice,” one grower said at a
contentious 2008 meeting. “It’s a waste of our money.”
“The public is already eating tons of G.M.O.’s,” countered Peter McClure, a big grower.
“This isn’t like a bag of Doritos,” snapped another. “We’re talking about a raw product, the essence of orange.”
The genetically modified foods
Americans have eaten for more than a decade — corn, soybeans, some
cottonseed oil, canola oil and sugar — come mostly as invisible
ingredients in processed foods like cereal, salad dressing and tortilla
chips. And the few G.M.O.’s sold in produce aisles — a Hawaiian papaya,
some squash, a fraction of sweet corn — lack the iconic status of a
breakfast drink that, Mr. Kress conceded, is “like motherhood” to
Americans, who drink more of it per capita than anyone else.
If various polls were to be believed, a third to half of Americans would
refuse to eat any transgenic crop. One study’s respondents would accept
only certain types: two-thirds said they would eat a fruit modified
with another plant gene, but few would accept one with DNA from an
animal. Fewer still would knowingly eat produce that contained a gene
from a virus.
Seven Genetically Engineered Foods
In a polarized debate over foods known as genetically modified organisms, or G.M.O.’s, such crops are often portrayed as universally either good or bad. Here is an assortment of crops that were modified with different genes, for different purposes, at different times.-
Tomato
-
Soybeans
-
Corn
-
Cassava
-
Apple
-
Rice
-
Salmon
Tomatoes with a longer shelf life
In 1994, the Flavr Savr tomato became the first G.M.O. to be sold to consumers. A California biotechnology start-up called Calgene inserted a reverse copy of a gene that makes the fruit soften, interfering with the gene’s production and extending the tomato’s shelf life. Though it was popular with consumers, the tomato was removed from the market when it proved too expensive to produce and ship.
There also appeared to be an abiding belief that a plant would take on
the identity of the species from which its new DNA was drawn, like the
scientist in the movie “The Fly” who sprouted insect parts after a
DNA-mixing mistake with a house fly.
Asked if tomatoes containing a gene from a fish would “taste fishy” in a
question on a 2004 poll conducted by the Food Policy Institute at
Rutgers University that referred to one company’s efforts to forge a frost-resistant tomato
with a gene from the winter flounder, fewer than half correctly
answered “no.” A fear that the genetic engineering of food would throw
the ecosystem out of whack showed in the surveys too.
Mr. Kress’s researchers, in turn, liked to point out that the very
reason genetic engineering works is that all living things share a basic
biochemistry: if a gene from a cold-water fish can help a tomato resist
frost, it is because DNA is a universal code that tomato cells know how
to read. Even the most distantly related species — say, humans and
bacteria — share many genes whose functions have remained constant
across billions of years of evolution.
“It’s not where a gene comes from that matters,” one researcher said. “It’s what it does.”
Mr. Kress set the surveys aside.
He took encouragement from other attempts to genetically modify foods
that were in the works. There was even another fruit, the “Arctic
apple,” whose genes for browning were switched off, to reduce waste and
allow the fruit to be more readily sold sliced.
“The public is going to be more informed about G.M.O.’s by the time
we’re ready,” Mr. Kress told his research director, Michael P. Irey, as
they lined up the five scientists whom Southern Gardens would
underwrite. And to the scientists, growers and juice processors at a
meeting convened by Minute Maid in Miami in early 2010, he insisted that
just finding a gene that worked had to be his company’s priority.
The foes were formidable. C. liberibacter, the bacterium that kills
citrus trees by choking off their flow of nutrients — first detected
when it destroyed citrus trees more than a century ago in China — had
earned a place, along with anthrax
and the Ebola virus, on the Agriculture Department’s list of potential
agents of bioterrorism. Asian citrus psyllids, the insects that suck the
bacteria out of one tree and inject them into another as they feed on
the sap of their leaves, can carry the germ a mile without stopping, and
the females can lay up to 800 eggs in their one-month life.
Mr. Kress’s DNA candidate would have to fight off the bacteria or the
insect. As for public acceptance, he told his industry colleagues, “We
can’t think about that right now.”
The ‘Creep Factor’
Trim, silver-haired and described by colleagues as tightly wound (he
prefers “focused”), Mr. Kress arrives at the office by 6:30 each morning
and microwaves a bowl of oatmeal. He stocks his office cabinet with
cans of peel-top Campbell’s chicken soup that he heats up for lunch.
Arriving home each evening, he cuts a rose from his garden for his wife.
Weekends, he works in his yard and pores over clippings about G.M.O.’s
in the news.
Readers’ Perspectives
“There may be good reasons not to
genetically modify organisms, but I don't see how the risk of gene
transfer, a widely observed process in nature, is one of them. ”
For a man who takes pleasure in routine, the uncertainty that marked his
DNA quest was disquieting. It would cost Southern Gardens millions of
dollars just to perform the safety tests for a single gene in a single
variety of orange. Of his five researchers’ approaches, he had planned
to narrow the field to the one that worked best over time.
But in 2010, with the disease spreading faster than anyone anticipated,
the factor that came to weigh most was which could be ready first.
To fight C. liberibacter, Dean Gabriel at the University of Florida had
chosen a gene from a virus that destroys bacteria as it replicates
itself. Though such viruses, called bacteriophages (“phage” means to
devour), are harmless to humans, Mr. Irey sometimes urged Mr. Kress to
consider the public relations hurdle that might come with such a
strange-sounding source of the DNA. “A gene from a virus,” he would ask
pointedly, “that infects bacteria?”
But Mr. Kress’s chief concern was that Dr. Gabriel was taking too long to perfect his approach.
A second contender, Erik Mirkov of Texas A&M University, was further
along with trees he had endowed with a gene from spinach — a food, he
reminded Mr. Kress, that “we give to babies.” The gene, which exists in
slightly different forms in hundreds of plants and animals, produces a
protein that attacks invading bacteria.
Even so, Dr. Mirkov faced skepticism from growers. “Will my juice taste like spinach?” one asked.
“Will it be green?” wondered another.
“This gene,” he invariably replied, “has nothing to do with the color or taste of spinach. Your body makes very similar kinds of proteins as part of your own defense against bacteria.”
When some of the scientist’s promising trees got sick in their first
trial, Mr. Kress agreed that he should try to improve on his results in a
new generation of trees, by adjusting the gene’s placement. But
transgenic trees, begun as a single cell in a petri dish, can take two
years before they are sturdy enough to place in the ground and many more
years to bear fruit.
“Isn’t there a gene,” Mr. Kress asked Mr. Irey, “to hurry up Mother Nature?”
For a time, the answer seemed to lie with a third scientist, William O.
Dawson at the University of Florida, who had managed to alter fully
grown trees by attaching a gene to a virus that could be inserted by way
of a small incision in the bark. Genes transmitted that way would
eventually stop functioning, but Mr. Kress hoped to use it as a stopgap
measure to ward off the disease in the 60 million citrus trees already
in Florida’s groves. Dr. Dawson joked that he hoped at least to save the
grapefruit, whose juice he enjoyed, “preferably with a little vodka in
it.”
Ricke
Kress, president of Southern Gardens Citrus, spoke to California citrus
growers about his efforts to create a transgenic orange resistant to
disease. He warned them, though, “If we don’t have consumer confidence,
it doesn’t matter what we come up with.” Gary Kazanjian for The New York Times
But his most promising result that year was doomed from the beginning:
of the dozen bacteria-fighting genes he had then tested on his
greenhouse trees, the one that appeared effective came from a pig.
One of about 30,000 genes in the animal’s genetic code, it was, he ventured, “a pretty small amount of pig.”
“There’s no safety issue from our standpoint — but there is a certain
creep factor,” an Environmental Protection Agency official observed to
Mr. Kress, who had included it on an early list of possibilities to run
by the agency.
“At least something is working,” Mr. Kress bristled. “It’s a proof of concept.”
A similar caution dimmed his hopes for the timely approval of a
synthetic gene, designed in the laboratory of a fourth scientist, Jesse
Jaynes of Tuskegee University. In a simulation, Dr. Jaynes’s gene
consistently vanquished the greening bacteria. But the burden of proving
a synthetic gene’s safety would prolong the process. “You’re going to
get more questions,” Mr. Kress was told, “with a gene not found in
nature.”
And in the fall of 2010, an onion gene that discouraged psyllids from
landing on tomato plants was working in the Cornell laboratory of Mr.
Kress’s final hope, Herb Aldwinckle. But it would be some time before
the gene could be transferred to orange trees.
Only Dr. Mirkov’s newly fine-tuned trees with the spinach gene, Mr.
Kress and Mr. Irey agreed, could be ready in time to stave off what many
believed would soon be a steep decline in the harvest. In the fall of
2010, they were put to the test inside a padlocked greenhouse stocked
with infected trees and psyllids.
How the culture you will work ?
in my experience, the 2.4 D is better than TDZ, TDZ aid in the formation of callus, but not in the high frequency. but also a higher concentration of 2,4-D, you will have more chance of mutations
2,4D coud be good when you put togheter another citokin... But what is important know is : How culture our friend will work ,, what do you think ?
or will have no practical help
place of callous and callous is a carbohydrate substance(similar to cellulose)
deposited on sieve elements,very different from your undifferentiated parenchymatic
callus.