BUZZ-Petra Diamonds: Rises on Bank of America Merrill Lynch upgrade
** Petra Diamonds (LSE: PDL.L - news) up as much as 4.7 pct after Bank of America Merrill Lynch upgrades to buy from hold
** "Given Petra's recent downgrade to pricing guidance (and subsequent consensus earnings revisions) we believe that the issue around rough diamond pricing weakness is now more understood by the market," analysts say in note
** "While channel checks suggest the market for rough diamond remains tepid we see limited evidence to suggest the pricing outlook is worsening", analysts add
** Peer Gem Diamonds down 1 pct in thin trading
** Stock has lost 13 pct since the beginning of the year to Tuesday's close
** Of the 16 brokerages covering the stock, two have a "hold" rating, one "sell" and 13 have "buy" or higher rating (venkateshasoumithri.mamidipudi.thomsonreuters.com@reuters.net)