Shares of Diamond Foods Inc. gained the most in more than a year after BlackRock Inc. said it took a stake in the producer of Diamond walnuts and Kettle Chips.

The shares advanced 15.2 percent to end at $16.60 in New York, for the biggest intraday jump since December 2011.

BlackRock, the world’s biggest money manager, disclosed it had taken a 7.9 percent stake in Diamond, according to a filing.

The San Francisco-based food company in November restated earnings for its fiscal 2010 and 2011 years after finding that certain payments to growers were booked to the wrong periods.