Citigroup said it built up its loan-loss reserves by $250 million in the fourth quarter to cover risks in its portfolio of energy loans—part of an overall reserve buildup of $494 million, or $588 million including unfunded lending commitments. It was the first time since 2009 that Citigroup has added to its rainy-day reserves for soured loans instead of releasing them. Wells Fargo had $90 million in higher losses in its oil and gas portfolio during the fourth quarter, and the bank said it boosted its commercial-loan reserves as a result. Wells as a whole had neither a buildup nor a release of reserves during the quarter because the energy-loan problems were offset by continued credit improvement in Wells’ portfolio of residential real-estate loans. The moves by Citigroup and Wells Fargo spotlight the concern on Wall Street that the recent plunge in oil prices could leave some borrowers in […]