A new winegrape variety trial at the Kearney Agricultural Research and Extension Center may help local vintners add a touch of distinction to San Joaquin Valley wines. During Kearney Grape Day, Aug. 16, UC Cooperative Extension viticulture specialist James Wolpert introduced growers to the 55 unusual varieties from Portugal, Spain, Italy and France being evaluated at Kearney. But don't expect to see these exotic red and white wine varietals - such as Corvina Veronese, Forastera, Trebbiano Toscano and Petit Manseng - on wine labels any time soon.

The research aims to give vintners blending varieties that will make San Joaquin Valley wines with familiar names more interesting. Vintners may use up to a quarter of their grape volume to impart distinctive color, flavor and structure to a varietal wine without calling it a blend. Grapes being studied at Kearney may one day add a certain flavor note - such as cherry, tannin, black pepper or citrus - to fine San Joaquin Valley wine.

Wolpert said the study represents the widest range of varieties evaluated in a public San Joaquin Valley trial in more than a generation. Characterization of the fruit composition is taking place in variety evaluations in Europe, however, such information rarely includes growing data, an important factor for Valley farmers.

"High levels of color and tannin cannot compensate for a variety whose yield is far below the economic threshold," Wolpert said.

At another stop on the Grape Day tour, UC Cooperative Extension viticulture farm advisor Mark Battany demonstrated the "Paso Panel." Battany developed the tool - composed of an inexpensive, lightweight solar panel and digital meter mounted on an aluminum frame - to help farmers fine tune their irrigation scheduling.

The Paso Panel allows farmers and researchers to quickly and easily calculate the amount of canopy shade in a vineyard or a vineyard row. The data can be combined with climate data to calculate crop water needs.

Measuring soil moisture and using plant-based monitoring systems are other ways to determine plant water needs, but Battany said currently climate-based methods are underused.

"A lot of farmers guess when they need to irrigate," Battany said. "People tend to guess on the conservative side, and put on more water than necessary."

New York-based USDA-ARS plant breeder Peter Cousins was also at the field day to explain his grape root stock variety trials planted at the Kearney Agricultural Research and Extension Center. Cousins and his staff screen 3,000 to 4,000 seedlings a year. The best prospects are sent to California, where 140 experimental root stocks are growing.

"Here at Kearney, the vines grow so vigorously, we can get more than 100 cuttings per plant," said Cousins. "This is their last stop, where we determine whether you can grow them in a field and make wood that propagates vines."

Some people say rabbiteye blueberries get their nickname from the circle on the blossom end the fruit. Others say the fruit's tendency to turn pink before going blue is reminiscent of a rabbit's eye. Whatever the reason, late ripening rabbiteye blueberries can provide San Joaquin Valley growers the ability to harvest fruit through the end of August, capturing a potentially lucrative market window, says UC Cooperative Extension farm advisor Manuel Jimenez.

Jimenez hosted blueberry growers at the Kearney Agricultural Research and Extension Center today to test the taste and texture of late-season blueberries. The participants also saw Jimenez demonstrate proper pruning techniques and had the opportunity to practice pruning on blueberry plants in Jimenez' test plots.

Porterville blueberry farmer Young Kwun attended the meeting with his farm manager Miguel Jaramillo Garcia. Kwun asked Jimenez how to replant blueberry bushes that had died.

"You can't do it," Jimenez replied. In the test plots, Jimenez and his staff replanted 60 blueberry bushes, and none of them survived. He tried a second time with the same result, and then inquired with blueberry growers around the country, finding that they also could not replant blueberries.

"Replanting is an issue with blueberries," Jimenez said. "We don't know what it is."

"You just saved me a bunch of money," said Kwun, whose 70-acre farm has a number of blank spots.

Kwun said he has missed the last few blueberry field days at Kearney, but that won't happen again.

"I'm thinking I should come every year," Kwun said. "I learned a lot."

The UC Riverside avocado breeding program has identified a promising new avocado variety, which scientists believe will soon take off commercially.

The GEM avocado is the great-granddaughter of Hass avocado, which is currently the industry standard in California. GEM has all the excellent characteristics of Hass avocados - creamy, nutty flesh; dark, pebbly skin when ripe - and it has additional benefits for the grower, according to Mary Lu Arpaia, a UC Cooperative Extension subtropical horticulturist based at the UC Kearney Agricultural Research and Extension Center in Parlier, Calif.

"Hass avocados are alternate bearing - they will produce a big crop one year, and a small crop the next. GEM is more consistent, so growers can make money every year," Arpaia said. "The trees are also more compact, which means growers have less costs for harvesting and tree maintenance."

GEM was part of an extensive avocado variety breeding program led since the 1950s by UC Riverside plant breeder Bob Bergh. Arpaia took over the program in 1996.

In the early 1980s, Bergh released a variety he called the Gwen. However, Gwen didn't turn black when it ripened, a disadvantage because consumers are accustomed to Hass. In the mid 80s, Bergh planted more than 60,000 avocado variety seedlings on farms across Southern California. GEM, a granddaughter of Gwen, was one.

There are GEM trees growing at the UC South Coast Research and Extension Center in Irvine. Fruit samples are sent to the Kearney Sensory Laboratory, where volunteers judge the fruit's outward appearance and compare the flavor with Hass.

Recently, UC Riverside signed an exclusive license agreement with Westfalia Fruit Estates, a South African company, to market GEM around the world, the university announced. In the United States, the California–based Brokaw Nursery has non-exclusive rights to the GEM avocado.

For information on GEM avocado sensory testing, see the one-minute video below.

Read a transcript of the video.

Peter Cousins of the USDA-ARS in Geneva, N.Y., will be referring to these charts during his presentation at Kearney Grape Day. The title of Cousins' presentation is "The development of new grape rootstocks for the San Joaquin Valley."