More seedless on the grapevine

Lauren CelenzaCountryman
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It’s all about the seedless varieties of many fruits these days, as consumers search for clean and easy-to-eat food.

Four table grape varieties have dominated new plantings in WA for several years, including seedless varieties Flame Seedless, Dawn Seedless and Crimson Seedless and seeded Red Globe.

The Department of Agriculture and Food’s Gascoyne research station (GRS) has been researching new seedless varieties to complement early season Carnarvon grapes.

Project manager Chris Shelfhout said the research vineyard was evaluating the possibility of growing new variety selections in Carnarvon.

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“One of the main advantages of growing table grapes in Carnarvon is the early season compared to the rest of the State, ” he said.

“The varieties growers really like are early season ones because there is a gap in the market then.

“Grape harvest in Carnarvon usually starts in mid to late November, beginning with Flame Seedless and Millennium Muscat, so if we can find some white seedless varieties that come into that part of the season it will complement the red seedless grapes.”

Mr Shelfhout said the GRS had been working closely with the CSIRO’s breeding program based in Victoria.

“At the moment we are evaluating a mid-to-late season white seedless which is very close to being released, ” he said.

“Essentially, we are looking for replacements or varieties that will fill gaps in the market.

“It’s a case of looking at how they grow and how they respond to various Gibberillic acid treatments, which is an essential part of seedless grape production.”

Gibberillic acid is a plant hormone that is normally produced in the seed. It regulates growth, increases berry size and helps stretch out bunches.

“Different varieties respond to different rates, so it’s an important thing to test, ” Mr Shelfhout said.

How the new grape varieties responded to different times of pruning was also being assessed.

“They have been bred from a wide selection of varieties, so a lot of them are hit and miss in Carnarvon, ” Mr Shelfhout said.

“There are some that just don’t produce and others that do really well.”

The mid-to-late season white seedless close to release should be joined by three other seedless varieties soon.

GRS is also researching bunch abortion which sometimes occurs in Carnarvon.

“One of the phenomena we have in Carnarvon with table grapes is bunch abortion, ” Mr Shelfhout said.

“Often growers prune in June/July and use a chemical called Dormex, which is a dormancy-breaking substance.

“The buds burst, then they go through a sick period and the young flowers abort and drop off, which significantly affects yield.

“We are not sure why it happens, but we are working with the University of WA to find out.”

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