As previously reported, Barclays analyst Karen Short upgraded Whole Foods (WFM) to Overweight from Equal Weight and raised her price target on the stock to $48 from $38, telling investors that she would not be surprised to see a bidding war break out following Amazon's (AMZN) announcement of a takeover agreement.

Short, who thinks a strategic retail buyer would generate up to $600M in synergies from a deal to buy Whole Foods, said bidders could include Kroger (KR), Target (TGT), and Wal-Mart (WMT), all of which may "have too much to lose not to bid."