Berkshire Hathaway Inc. disclosed a stake in Verizon Communications Inc. as Warren Buffett’s backup stock pickers build their portfolios. Verizon gained in extended trading in New York.

Berkshire held 11 million shares of the telecommunications company on March 31, Buffett’s Omaha, Nebraska-based company said today in a regulatory filing. The stake is valued at about $528.7 million based on today’s closing price. Berkshire also added to its stake in Wal-Mart Stores Inc.

Verizon boosted its cash flow by acquiring Vodafone Group Plc’s minority stake in Verizon Wireless in February, meaning it no longer had to pay a dividend to the U.K. carrier. The $130 billion deal was a bet that the U.S. wireless market still has room for growth even though a majority of U.S. users already have smartphones. The company has forecast higher adjusted profit margins this year on a 4 percent increase in revenue.

“Verizon no longer has deal risk potential after the Vodafone transaction so it looks like a safe harbor with a decent risk-reward profile,” said Todd Lowenstein, a portfolio manager with Highmark Capital Management Inc.

Verizon is the 24th-highest payer of dividends in the Standard & Poor’s 500 Index, with a yield of 4.4 percent, according to data compiled by Bloomberg. Bob Varettoni, a spokesman for New York-based Verizon, declined to comment on Berkshire’s stake.

Buffett’s deputy investment managers Todd Combs and Ted Weschler have been reshaping Berkshire’s stock portfolio since being hired in 2010 and 2011, adding stakes in companies like DaVita HealthCare Partners Inc. and DirecTV. The money managers benefit from being able to make smaller investments, while their boss focuses on multibillion dollar wagers and overseeing holdings he amassed years ago.

Hiring Weschler, 52, and Combs, 43, was a cornerstone of Buffett’s succession plan at Berkshire. The CEO has said they will jointly oversee all investments once he’s no longer leading the business he built over the past five decades from a failing textile maker into one of the most-valuable companies in the world. Its market capitalization surged past $300 billion this year for the first time, buoyed by gains in the stock portfolio and earnings from dozens of operating businesses.

That track record has earned Buffett a following among investors, who study his stock picks for clues about Berkshire’s strategy. His major equity purchases can often send a company’s shares higher. When Buffett reported a $3.7 billion stake in Exxon Mobil Corp. in November, the world’s biggest oil explorer gained 2.2 percent the following day and closed at its highest level in at least 33 years.

Verizon advanced 1.6 percent to $48.74 at 5:54 p.m.

Verizon’s largest shareholders include Capital Group Cos., manager of the American Funds mutual funds; BlackRock Inc.; and Vanguard Group Inc., each with more than 200 million shares, according to data compiled by Bloomberg. Billionaire hedge fund manager John Paulson today disclosed a stake of 8.7 million shares.

Berkshire’s stake in General Motors Co. declined by 25 percent to 30 million shares. The holding of DirecTV fell to 34.5 million shares from 36.5 million three months earlier.

The number of Wal-Mart shares climbed by 17 percent to about 58.1 million shares. The stake in the Bentonville, Arkansas-based retailer is valued at $4.46 billion, based on today’s closing price of $76.83.

Buffett, 83, has long championed a concentrated, patient approach to stock investing. More than half of Berkshire’s $118.5 billion equity portfolio at the end of March was in four companies: Wells Fargo & Co., Coca-Cola Co., American Express Co. and International Business Machines Corp. Except for the IBM holding, which Buffett began accumulating in 2011, all have been in the portfolio since at least the 1990s.

The deputies each oversee about $7 billion on behalf of Berkshire insurance units and the pension funds for various subsidiaries. Both outperformed the S&P 500 in 2012 and 2013.