Marks & Spencer has unveiled the boss of supermarket Morrisons, Marc Bolland, as its new chief executive.He will take up the position in the new year.Sir Stuart Rose will continue as part-time chairman of M&S to ensure a smooth transition and will leave M&S by July 2011.'M&S is one of the world's great brands and I am very pleased to be given the opportunity to lead the company forward at this exciting stage,' said Bolland. 'I am greatly looking forward to working closely with Stuart and the M&S team.'Bolland joined Morrisons in September 2006, helping the Bradford-based supermarket recover from its problematic acquisition of Safeway.Shares in M&S immediately jumped on the news, which ends the long-running saga of its search for a new chief executive, but Morrisons shares fell sharply into the red.