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UF/IFAS Researcher Opens Door To Crop-Ripening Manipulation

GAINESVILLE—A University of Florida researcher has tracked down a mutant gene responsible for thwarting the ripening of a tomato — thereby raising hopes for the widespread manipulation of ripening in numerous fruits, vegetables and flowers.

The ultimate result of research by UF Eminent Scholar and Professor Harry J. Klee is likely to have substantial economic benefit to Florida. Producers will be able to ship more mature — and tastier — produce while reducing the risk of spoilage, predicted one UF expert with the Institute of Food and Agricultural Sciences.

“I think the impact is almost immeasurable,” said postharvest physiologist Jeff Brecht about just the impact on tomatoes. “It would overcome the major problem we have with tomatoes.”

The tomato is the No. 1 vegetable crop in Florida, accounting for about half of the total value of vegetable crops and generating about $700 million in economic impact annually, Brecht said.

The efforts of Klee are detailed in the Dec. 15 edition of “Science.” Klee said his breakthrough built upon equally pioneering work, also featured in the Dec. 15 edition of “Science,” of University of Wisconsin-Madison plant scientists Anthony Bleecker and Eric Schaller.

Much of the research has focused upon plant ripening, which comes about through the presence of a hormone, ethylene. “It is an extremely important hormone,” Klee said. “It is the compound that controls fruit ripening in many species — many that are critical to Florida horticulture.”

The substance already is applied to many crops to speed up ripening. The fruit are picked green to avoid the difficulties of handling ripe fruit — they are easily bruised and more likely to rot — then later encouraged to ripen by ethylene treatment.

But the problem could be overcome more efficiently, and with better final quality, by genetically engineering plants with delayed ripening cycles.

Bleecker and Schaller used a weed, Arabidopsis, to detail how, in genetic terms, the plant recognizes, and then inhibits, ethylene. Klee used their work to guide him to the specific gene that greatly slowed the ripening in the Never-ripe tomato.

Klee, who directed a team that included Jack Q. Wilkinson of Monsanto, Michael B. Lanahan of Ciba-Geigy and Hsiao-Ching Yen and James J. Giovannoni of Texas A&M University, took the model developed by Bleecker and Schaller and applied it to specific — and economically important — research.

“We’ve been very interested in understanding how ethylene works and how it controls this process of ripening,” Klee said. “How does the plant see ethylene?…And why (sometimes) doesn’t it see ethylene.”

Klee’s research is likely to extend the life of a variety of crops and allow Florida fruits, vegetables and flowers to be shipped to even the most distant of markets.

The tomato, for example, is generally harvested when about 85 percent of the crop is still green and hard, Brecht said. Even with ethylene application, many of these tomatoes, particularly winter tomatoes, don’t reach full flavor and ripeness at market.

But if the ripening could be manipulated, Brecht said, the tomato could be harvested at a more mature stage and reach the market in a tastier condition.

Both Klee and Brecht said the additional life given the tomato would make it easier to ship the crop into more distant markets around the globe. Brecht added that the tastier tomato would likely encourage greater consumer demand; surveys show many consumers pass on tomatoes because they don’t have the fully ripe flavor.

And, Klee adds, there is no visible hurdle to applying the research beyond tomatoes to dozens of other crops.

“Now the world is open to us in terms of being able to manipulate ethylene for crop production,” Klee said. “There is no reason to believe we can’t extend this to many other species.

“Basically, the sky’s the limit.”

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