Varietal differences affect grapevine water deficit reaction

The annual International Conference on the Status of Plant and Animal Genome Research at the Town and Country Hotel in San Diego includes a grape genome session, and this year’s January 12 session at the January 11-15 conference included the presentation “Label-Free Proteomic Analysis of Five Grapevine Cultivars Under Water Deficit”.

Ryan Ghan of the University of Nevada was the presenting author. He was assisted in his research by Daniel Hopper and Grant Cramer of the University of Nevada and by Steve Van Sluyter, Dana Pascovici, and Paul Haynes of Macquarie University in Australia. The study analyzed chardonnay, cabernet sauvignon, merlot, pinot noir, and semillon grapevines.

“Basically the biggest thing we see is the varietals themselves are contributing to change,” Ghan said.

Ghan studied grapes harvested during the June-November growing season in 2011.

“Overall we had very little rain,” he said.

With the exception of the pinot noir grapes, the size of the grapes was not significantly affected by the lack of water.  

“For the most part our water deficit treatment really had no effect on berry diameter,” Ghan said.

(The control pinot noir berries were an average of 12.09 centimeters in diameter while the deficit-stressed berries averaged 11.51 centimeters.)

Ghan extracted proteomic information from harvested berries to determine the effect of drought stress on proteins. The cabernet sauvignon grapes had 2,155 total proteins with 2,025 unchanged, 61 upregulated (intensified), and 69 downregulated (diminished). There were 2,306 merlot proteins with 2,207 unchanged, 64 upregulated, and 35 downregulated. The 2,147 pinot noir proteins had 2,054 unchanged, 62 upregulated, and 51 downregulated. The breakdown for the 2,019 chardonnay proteins was 1,882 unchanged, 98 upregulated, and 39 downregulated. The 2,161 semillon proteins consisted of 1,909 unchanged, 143 upregulated, and 109 downregulated proteins.

“In each case there are independent proteins that are just subsets that are different,” Ghan said.

Ghan found 1,567 proteins which were shared across the varietals, including 1,208 which could be quantified.

“For the most part what we saw was big varietal differences,” Ghan said.

Some of the mechanisms berries utilize to survive under drought stress have taste implications.  

“Some of these products are beneficial to us,” Ghan said.

Ghan is originally from Gardnerville, Nevada, and started making wine with his family before studying grapevines. He expects to receive his PhD by the end of the summer.  

“It’s been about a ten-year process,” he said. “But it’s been awesome.”

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