Upbeat Supervalu results boost U.S. grocery stocks

July 25 (Reuters) - Shares in Supervalu Inc jumped 13 percent on Tuesday and were headed for their biggest one-day gain in four years after the grocery wholesaler and retailer reported quarterly sales that topped some analyst expectations.

The results boosted other grocery shares that have taken a beating since Amazon.com Inc in June announced plans to buy Whole Foods Market Inc for $13.7 billion.

Wal-Mart Stores Inc Kroger Co and United Natural Foods Inc each rose more than 2 percent.

"The industry is up in sympathy with Supevalu," said Pivotal Research analyst Ajay Jain.

On top of the competitive threat from Amazon.com, falling food prices have eaten into the grocery store industry's profit margins.

Supevalu reported fiscal first-quarter net sales of $4 billion, up 6.3 percent and marginally higher than average analyst expectations, according to Thomson Reuters data.

The company's wholesale net sales rose 12.4 percent in the quarter, an increase that Jain said was better than he expected.

Supervalu shares were up 42 cents at $3.67 and on track for their largest one-day percentage gain since 2013. The shares were still down 21 percent year to date, however, even with Tuesday's gain. (Reporting By Marc Vartabedian; Editing by Meredith Mazzilli)