Bank of America is in talks to sell a major portion of Merrill Lynch’s real estate portfolio to the Blackstone Group for up to $1 billion, a person briefed on the matter told DealBook on Tuesday, as the bank seeks to raise additional capital. The holdings in question include a variety of commercial properties and real estate stakes around the world, said this person, who spoke on condition of anonymity because the talks were continuing and might fall apart. A sale would be the latest effort by Bank of America to sell noncore assets to help shore up its balance sheet. Bank of America’s stock has slumped 25.7 percent over the last month, propelled in part by investor fears that the bank would need to sell additional shares.