Citrus biotech: A chance with catch

Biotechnology presents both an exciting opportunity and a challenge for the California citrus industry, says Ted Batkin, president of the Citrus Research Board.

“It is a very useful tool that can move our industry in very positive directions, if we plan for it properly,” Batkin told a recent grower seminar conducted by the board at Parlier.

Yet the process could take 20 years to achieve desired varieties and resistances to insects and diseases, along with satisfying human and environmental health issues under regulations yet undefined.

“We have to make darn sure what we do is fully tested before it is released. If something harmful to human health hits the market, it's too late. We have to carefully plan strategies.”

Foremost in any strategy is the citrus industry being well attuned to public opinion. “We can't assume we know what the public is actually thinking. We can be our own worst enemies at times when we think we know what everybody wants.”

Batkin, a fourth generation California grower who has guided the California marketing order's citrus research activities since 1993, said citrus growers have not always grasped that the public does not rush to buy an orange just because it is great tasting and juicy. Those traits account for little if the fruit is full of seeds and its rind is green, two criteria that motivate consumers.

Threshold for citrus

Biotechnology, until recently, has been something involving tomato, corn, and other crops, he said. But for citrus, genetically modified organisms, or GMOs, are at a threshold.

Molecular biology, particularly, figures prominently since it enables study of plants at the most basic level, opposed to the time-consuming classical methods of growing out plants and observing them.

Broader than GMOs alone, molecular biology allows rapid molecular “fingerprinting” of traits of a plant to determine the variety of scions or rootstocks.

As an additional advantage, the science can isolate certain genes and transform them into new varieties far more rapidly than chance discovery of “sports” in the field, followed by scientists and growers developing varietal improvements from them over a period of many years.

Unfortunately, the new ways based on laboratory procedures also mean researchers lose touch with growers' concerns at the field level. Batkin said the grower-funded research board has to find ways to bridge the gap.

The process of successfully placing genes in plants is hardly an overnight task itself. Getting the genes in place is only one step and is followed by lab testing to ensure it was indeed placed properly, propagation of the resulting plant for field testing, and evaluations before commercial release.

The countless processes unfold to a time span of about 20 years, using the technology at hand, from identification of a gene to be moved until the presentation of the desired fruit in the marketplace.

The citrus industry has advanced toward transformation technology, defined as moving a desired gene from outside a target plant into it. Breakthroughs with lemons, grapefruit, and sweet orange have occurred at laboratories in Florida, Texas, and California during the past year.

Three methods of transformation are in use. The most common is agrobacterium, a process patented by Monsanto. Batkin said the citrus industry may enter partnerships with Monsanto in developing new varieties.

Another method developed at Pennsylvania State University uses sound waves to move genes into a target plant, while the third, under development at the University of California, Riverside, uses a particle-gun device to install genes.

Getting back to the projects at hand, Batkin said plants now in laboratories are still quite young and have yet to be evaluated in the field.

True resistance

The top priority of the board is to develop citrus rootstocks truly resistant to citrus tristeza virus and not simply tolerant of the disease as present trifoliate rootstocks are.

Although the disease is the source of quick decline in sour orange rootstock, it moves more slowly with trifoliate but still causes lower yield and smaller fruit size.

A Texas A&M University researcher working with grapefruit plants for resistance to citrus tristeza virus found that the resistance was in place but was not taken up by the plants because of the “construct,” or method of moving the genes.

Earlier flowering is another goal, and experimental molecular work in Spain saw the insertion of a gene to accomplish just that. While not applicable to commercial use, it will allow evaluation of flowering traits of experimental cultivars in two rather than four or five years.

But Batkin warned that molecular biology has its downside, particularly when it comes to incorporating cold tolerance to citrus, after which California-developed technology might become available to other regions where competing fruit could be grown. The board discourages research on this issue.

“In the San Joaquin Valley, we may think it's a great thing to prevent loss in a freeze, but citrus having cold tolerance could also be grown in Wenatchee, Washington. We have to be careful with this technology to make sure we don't shoot our self in the foot.”

Insect resistance, while seemingly an obvious advantage, can have its trade-offs. “We have proteins we can insert into a tree to make it lethal to red scale — for about two years until resistance sets in. So why invest in a project that gives us trees that are no longer resistant by the time they are in production?”

A Texas researcher, he continued, claims to have come up with a protein that when inserted in citrus can create resistance to glassy-winged sharpshooter or other sucking insects.

Research priorities

“Great idea, but the protein is also highly toxic and highly allergenic, not what we'd want in our oranges,” he said.

With this sort of background, the greater citrus industry needs to consider what its research priorities are, a formidable job of blending realistic goals with available technology.

“We have to consider several factors, not just what happens inside the boundaries of our groves, but what happens to the crop and where it goes.”

Forging a strategy will require scientific discipline, Batkin said. “We can't have a free-for-all of anyone taking any gene to insert in a plant to move into commercialization. We expect the academic community to help us provide the discipline.”

He went on to say there are many private laboratories getting into the act, and that will have to be through a regulatory process.

But Batkin also said no regulatory structure is in place for the job and agency personnel are of opposing viewpoints on the entire subject of molecular biology, and he predicted “a lot of gnashing of teeth over the next five or six years.”

Although he said he does not favor an additional government, Batkin speculated that biotechnology, now regulated between the Food and Drug Administration, EPA, and USDA's Animal and Plant Health Inspection Service, will require “serious collaboration” between those agencies if not a new federal department.

e-mail: [email protected]

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