COMMODITIES-Broad losses as Q2 opens; corn,copper at 9-month low

* U.S., China factory data; weaker supply-demand disappoints * Cyprus bailout still a threat as Europe closed for Easter * Caution too before ECB meeting, US jobs data later in week * Dollar down versus euro, U.S. stocks retreat from Thurs record By Barani Krishnan NEW YORK, April 1 (Reuters) - Grains and metals markets extended their tumble into the second quarter, with corn and copper hitting nine-month lows on Monday amid weaker supply-demand fundamentals and disappointin