Among the nearly 160 varieties of citrus available for tasting at an event in Exeter, none appeared ready to upstage the seedless Tango mandarin that made its commercial debut about five years ago.

“I don’t think anything this year will take off as much as Tango did,” said Mikeal Roose, professor of genetics at the University of California at Riverside.

But that hardly dampened interest as scores of growers and their advisers sampled thousands of little pieces of fruit at the UC Lindcove Research and Extension Center.

Mandarins and navels were the leading categories in number of varieties. Others included satsumas, blood oranges, sweet oranges, tangelos, lemons, tangors, limes, pummelos, grapefruit, citron and kumquats.

Researchers including Roose have focused much of their attention on the mandarin and notably on varieties that have fewer or no seeds, said Beth Grafton-Cardwell, director of the Lindcove center.

She and Roose explained that irradiation of bud wood has been a key to stepping up mutation processes that can lead to a new desirable variety. The bud wood is grafted and planted at the Lindcove center for further evaluation.

Roose said it can take 15 years to come up with a commercial variety from the time irradiation is first done. He said one challenge now is to find varieties of seedless mandarins that could fill a gap in that variety from late February to early March.

Among new varieties of mandarins gaining favor is the Daisy, which has been available commercially since 2009. “It’s a marvelous piece of fruit, good color, fabulous flavor and low or no seeds,” said Tim Williams, a staff research associate in the Citrus Breeding, Genetics and Germplasm program at UC Riverside.

Williams said another lower-seeded variety of the Encore will be released in June 2012. It’s unusual in its appearance, bearing spots.

While those spots might be off-putting to shoppers, it’s not likely to be an absolute stumbling point, Williams said. Such distinctions can be used as an identifier to draw shoppers who recognize the fruit as good tasting. Williams cited the example of the Gold Nugget, which has a rough rind that has actually contributed to marketing success in Europe.

“It identifies that particular fruit,” Williams said.

Other relatively new low-seeded, irradiated mandarin varieties drawing interest include the Fairchild LS, released in January 2010 and the Kinnow LS, released in April 2011.

Dale Mehrten of Visalia talked with Williams about choices he’s looking at as replacements for flame seedless and red globe grape vines that he removed on 25 acres. He remarked that a neighbor has pummelos, and Williams said that can result in seeded citrus, making selection still more critical.

“I want something that comes off early,” Mehrten said.

Timing and taste

Those who attended the tasting took timing into consideration along with taste and other criteria.

Alex Del Rio, who works with Leffingwell Ag Sales Co. in Ivanhoe, Lindsay and Terra Bella, said he was looking basically for “good flavor, what can be sold fresh, sugar content, color and size. The consumer likes non-seeded products, although sometimes the seeded products taste better.”

His lips puckered as he sampled a Eustis limequat. “Sour, tangy,” he said.

A staffer at the center explained that that particular fruit had not fully ripened. “It’s not at its peak,” she said. That’s one of the challenges in staging the tasting – the variability in ripening by a given date.

Andrea Gjerde, a citrus and subtropical specialist with Entomological Services Inc. of Visalia, enjoyed a taste of the Oro Blanco grapefruit, which she said is not particularly seedy and is less likely than other citrus to be plagued by citrus thrips.

During the tasting, participants were also taken on a tour of the demonstration plots at the center where they could see some of the fruit they had tasted hanging from trees and also see fruit that wasn’t sampled.

Tracy Kahn, principal museum scientist with the Citrus Variety Collection at UC Riverside, conducted the tour with assistance from Tom Delfino, executive director of the California Citrus Nursery Society.

The two invited participants to pull fruit from trees, but told them not to cut or clip the trees or use any tools, a precaution against any spread of disease.

The demonstration block at Lindcove was started in 1994. Trees are propagated from bud wood provided by the Citrus Clonal Protection Program and are planted in blocks at the UC Riverside Citrus Variety Collection, at the Lindcove site and in Thermal at the Coachella Valley Agricultural Research Center.

At Lindcove, participants were able to see some of the cultivars recently introduced by the clonal program as well as some that have been grown commercially for nearly two decades.

Newer varieties included the Hansen mandarin developed in South Australia. It has good flavor from February to March, researchers said, but the fruit can be quite seedy.

Also on display was the Avana apireno, a selection of the Willowleaf mandarin. “Smell that smell,” Kahn said, as a powerful citrus smell wafted through the trees. “That’s the distinctive Willowleaf smell.”

Researchers say Avana apireno fruit reaches legal maturity by early December and has few seeds.

USDA 6-15-150 mandarins came out of Florida and are believed to be cold hardy.

Quirky

Kahn pointed to a couple quirky items in the demonstration grove. One was the California Rojo orange, which researchers suspect could be the Cara Cara. It may have been given a new name in Corsica, France.

Participants in the tour joked that a name change for the Cara Cara might be in order. “This is more romantic,” one said.

Kahn also showcased a varietal called Lemonade, pointing out that its origins appear to have been from bud wood brought unlawfully from New Zealand into the United States. She said the citrus clonal program took care to “clean up” bud wood because the tree was infested with viruses.”

She said what had to be done with the tree should serve as a strong reminder to growers to avoid unlawful planting of bud wood that has not been cleared for use. “It’s not the route you want to go, and you need to keep reminding your neighbors,” she said.

Kahn urged participants to attend a citrus day Jan. 26 at UC Riverside that will include discussions on Asian Citrus Psyllid, tours of the citrus variety collection and the U.S. Department of Agriculture national clonal germplasm repository and discussion of citrus flavors.