(Reuters) - The Dow Jones index fell more than 7% to a three-year low on Wednesday, moving into negative territory compared to levels when President Donald Trump took office and marking the latest landmark in Wall Street's most dramatic selloff in decades.At 12:36 p.m. ET the Dow Jones Industrial Average traded at 19,701.23 points, below the 19,732.40 points it closed at on Jan. 19, 2017, the day before Trump was inaugurated as the 45th U.S. president.As the coronavirus pandemic spreads deeper..