Apple shares tumbled Thursday (early Friday AEST), on track to wipe out $US200 billion ($313 billion) of market value in just two days, as China plans to expand a ban on the use of iPhones to government-backed agencies and state companies. Shares of the Cupertino, California-based company fell as much as 5.1 per cent, bringing its two-day slump to 6.8 per cent. Apple is the biggest component in major US equity indexes, adding to a broader selloff sparked in part by a litany of woes in China. The world’s second-biggest economy has been slumping amid a protracted crisis in its...