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Like Your Grapes Seedless? USDA Grape Research Program Celebrates 100 Years



Thanks to USDA research, grapes have evolved to meet the needs and desires of both consumers and growers over the past 100 years. (GV Wire/Paul Marshall)
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One hundred years ago, the U.S. Department of Agriculture started its Experiment Vineyard program in Fresno as part of its Bureau of Plant Industry.

And since that time, research from the facility has helped the Central Valley’s legacy crop survive environmental and economic challenges, as well as shifting consumer tastes.

On Monday, the USDA commemorated the century-long work done in Fresno and Parlier. The event brought out representatives from Sun-Maid Growers, the California Table Grape Commission, and Rep. Jim Costa (D-Fresno).

Over half of the top seedless grape varieties today came out of the USDA’s Agricultural Research Service, which relocated to Parlier in 2000, said Dr. Beto Perez de Leon, director of the ARS.

The ARS lab works with several different crops — including almonds and stone fruit, as well as raisin and wine grapes. But the focus of the lab is on table grapes.

“From the beginning, it was about developing varieties that had a desired, flavor, color, and also try to work the genetics to be harvested at the ideal time of the year,” said Perez de Leon.

ARS Lab Brought Seedless Grapes to the Forefront

The roughly 90,000 acres of table grapes in California account for 99% of the market, said Ross Jones, senior vice president and chief science and technology officer for the California Table Grape Commission.

The California Table Grape Commission helps fund the ARS lab.

“It’s been critical for the industry, some examples are developing new varieties like from USDA Breeding Program, new rootstocks, evaluating varieties.”

Research has created disease and pest resistance in grapes. Research into matters as mundane as safe handling has allowed grapes to last longer on the shelf. Now, growers ship grapes to 60 countries around the world.

Advancements in seedless grapes largely came from the breeding program. The Thompson seedless occurred naturally, Jones said. A mutation eliminated the seed from the iconic breed.

But it was researchers at the U.S. Department of Agriculture’s research program in Fresno who debuted the flame seedless varietal in 1973. The embryo transfer technique developed at the lab revolutionized grape breeding, Perez de Leon said. The technique allowed researchers to use seedless parents to produce seedless progeny.

Fifty years later, consumers can still find the red flame seedless on shelves. Seedless black grapes came out in 1983, said Perez de Leon.

“If you look at historical production numbers and charts, you can just see how essentially when seedless grapes came about then, just how that’s kind of changed the industry and changed production and changed global consumption,” Jones said. “Flame seedless gets a lot of credit.”

Grapes Brought Tens of Thousands to San Joaquin Valley

Grapes and especially raisins are the single most labor-intensive crop grown in the San Joaquin Valley, says Manuel Cunha, president of the Nisei Farmers League.

Vines need to be pruned, grape bunches need to be picked by hand and laid out by hand. In the case of raisins, they have to be laid out on trays and picked up.

In 1973, of the 166,000 acres of grapes in Fresno County, 143,701 were dedicated to raisins, according to the Fresno County Crop Report. Ten years before that, raisin vineyards occupied 138,372 acres.

For six weeks every year, upwards of 50,000 people would come to the Central Valley from Mexico solely to harvest grapes, Cunha said. It was a family activity. Both men and women would be in the field.

Children would bring the parents paper for laying grapes or bring them water.

“When they’re done, they go home because they’ve made enough money to survive and do well for the year,” Cunha said.

It was against conditions during the grape harvest in 1965 that labor leader Cesar Chavez led strikes and boycotts that resulted in the first United Farm Workers contracts signed in 1970.

Traditionally, grape harvesting has been labor-intensive. But it’s becoming increasingly mechanized thanks to advancements made through research. (Shutterstock)

Much Grape Research in Response to Labor Shortages

But as the decades continued, more crops arrived in the Central Valley coupled with fewer people willing to toil in the fields. Thus, grape growers had to fight for dwindling labor.

“In the 60s and 50s, we didn’t have all these 400 varieties of types of crops,” Cunha said.

A lot of research into different varietals has resulted from a desire to answer the needs of labor.

Grape research has made it easier to mechanize the harvest, said Perez de Leon.

“Through the years, there has been mechanization to be able to maximize the use of machinery with the harvesting of grapes,” Perez de Leon said.

Machines can now shake vines to lay grapes mechanically on paper to dry. This also allows grapes to be harvested at night, where colder temperatures prevent the berries from bursting, said Cunha.

This is made possible by looking for specific traits and researching in tandem with new mechanics.

Research for drying-on-the-vine methods also came from the ARS lab.

Cunha said grape research pushed research into other crops forward. Stone fruit harvests no longer use ladders, but rather moving platforms.

“This is all from the grape question,” Cunha said.

From left: Luis Martinez with state Sen. Anna Caballero’s office (D-Merced), Rep. Jim Costa (D-Fresno), Dr. Simon Liu, administrator USDA-ARS, Dr. Tara McHugh, director USDA-ARS Pacific West Area, Dr. Adalberto Perez de Leon, Director USDA ARS San Joaquin Valley Agricultural Sciences Center, and Dameane Douglas, field representative for Assemblymember Joaquin Arambula’s office (D-Fresno) celebrate 100 years of the USDA-ARS office’s grape research. (USDA)

Researchers Want to Grow Grapes Earlier, Longer

Work goes on at the ARS lab. Robotics continues to revolutionize the ag industry, and growers need to develop crops to allow for mechanized harvesting.

Growers want to have grapes ripen all at the same time, allowing for a single pass. More uniform clusters help with harvesting as well. The Table Grape Commission has been funding research to help automated systems identify grapes ready to be harvested.

At the lab, researchers are developing breeds that can begin growing earlier and last longer throughout the season, said Perez de Leon. This would help expand California growers’ presence on the world market.

“We scientists love what we do and it takes a lot of time and patience, then the Eureka moment comes and it’s very short-lived. But that’s when we are in nirvana,” Perez de Leon said.

Edward Smith began reporting for GV Wire in May 2023. His reporting career began at Fresno City College, graduating with an associate degree in journalism. After leaving school he spent the next six years with The Business Journal, doing research for the publication as well as covering the restaurant industry. Soon after, he took on real estate and agriculture beats, winning multiple awards at the local, state and national level. You can contact Edward at 559-440-8372 or at

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