Syngenta's (SYT) decision last year to begin selling biotech sugarbeet seeds in the U.S. has been extremely profitable, Chief Executive Michael Mack said Thursday.

Mack, who sat down with Dow Jones Newswires during the U.S. Department of Agriculture's annual Agricultural Outlook Forum, said Syngenta's U.S. market share for sugarbeet seeds rose to 35% in 2008, up from 19%.

Weed management in sugarbeet fields is a major issue for producers, Mack said, and the company's biotech seed is recognized for its ability to help because of its tolerance of glyphosate, a common herbicide.

"Farmers flocked to our germplasm and traits," Mack said.

Rival Monsanto Co. (MON) also has a biotech sugarbeet variety, which is also glyphosate-resistant.

The Monsanto variety was approved for use in 2005, but biotech sugarbeets in general took a while to gain popularity because food and environmental groups raised concerns about the safety of sugar made from genetically modified beets.

However, most countries with major sugar beet markets have approved herbicide-resistant varieties for use.

-By Bill Tomson, Dow Jones Newswires; 202-646-0088; bill.tomson@dowjones.com