SHANNON TWOMEY, The Weekly Times
January 5, 2017 8:00am
The sunpreme raisin grape is proving popular with producers because it costs less to harvest, according to Agricultural Research Service plant geneticist Craig Ledbetter.
He said the sunpreme dried without cane cutting and could save millions of dollars in production costs.
“With many grapes, crews must go out about two weeks before the harvest and cut the canes, which are the long branches on the vines that actually produce the grapes,” Mr Ledbetter said.
“Once the canes are cut, the grapes begin to wilt so they can be shaken into trays later.
“Cane cutting costs about $180 per hectare, which is roughly 36 per cent of total harvest costs.”
He said supreme grew well in the San Joaquin Valley, where roughly 80,937ha of raisin grapes a year were produced.
“So far, five nurseries have licences for the new green raisin grape, and some are already taking orders from grape producers,” he said.
Mr Ledbetter said along with his colleagues he compared the overall quality of sunpreme grapes which received three irrigation levels and two pruning techniques.
“The three irrigation levels were replacing 100 per cent of the water used by the vines and soil; reducing to 50 per cent water at berry softening; and a shock treatment where the vine was initially irrigated, then denied water for two weeks, and finally given a 50-percent water treatment,” he said.
Results showed that the shock treatment saved the most water, but it could be tricky to implement. A better alternative is to irrigate at a 50 per cent replacement level.”
US Department of Agriculture plant breeder David Ramming discovered sunpreme in the mid-1990s after crossbreeding raisin varieties that dried on the vine.
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