California raisin vineyard

Could Sunpreme variety help save California’s raisin industry?

The Sunpreme variety is great news for the California raisin industry currently hit hard by high production costs, decreasing consumer raisin demand, and rising product competition overseas.

The Sunpreme raisin grape can cost less to harvest and in essence keeps more money in growers’ pockets, says USDA’s Agricultural Research Service (ARS) in California who developed the grape varietal.

This is great news for the California raisin industry hit hard by high production costs, decreasing product demand, and rising raisin competition overseas.

With most vineyard varietals, work crews cut the canes with grape clusters attached about two weeks before harvest. The fruit then wilts and are shaken into trays later.

Under this traditional method, cane cutting costs about $130 per acre, or about 36 percent of total harvest costs, according to ARS plant geneticist Craig Ledbetter at the San Joaquin Valley Agricultural Sciences Center.

NO CANE CUTTING

With the new Sunpreme variety, raisin grapes dry without cutting the canes. This could save growers millions of dollars in production costs and improve their competitiveness in the world raisin market.

According to ARS, Sunpreme grows well in California’s infamous San Joaquin Valley where about 200,000 acres of raisin grapes are grown annually.

Sunpreme was bred and patented by now retired ARS horticulturalist David Ramming. Five nurseries have licenses for the new green raisin grape, and some are taking Sunpreme orders from raisin growers, ARS says.

SUNPREME COMPARISON

Ledbetter and his colleagues compared Sunpreme grape quality which received three different irrigation levels and two pruning techniques.

The three irrigation levels replaced 100 percent of the water used by the vines and soil; reducing to 50 percent water at berry softening; and a ‘shock treatment’ where the vine was initially irrigated, left un-watered for two weeks, and then given a 50 percent water treatment.

In the end, the shock treatment saved the most water, but it could be tricky to implement. ARS says a better alternative is to irrigate at a 50 percent replacement level.

The results also confirmed that Sunpreme vines only need spur pruning which generally requires less skill than cane pruning.

In the end, Ledbetter says spur-pruned vines produced grapes which were comparable in size, quality, and quantity compared to cane-pruned vines.

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