Shares in Tesco bucked the downward trend on Tuesday after UBS upgraded the supermarket titan from neutral to buy and added the stock to its 'Key Calls' list, highlighting that "driving higher returns is now at the heart of group strategy." A broad sell-off in commodities markets is providing a drag on miners Xstrata and Vedanta, while a falling Brent crude price is taking its toll on oil and gas engineer Weir Group, which is the Footsie's second worst performer, dropping over 8%. Goldman Sachs has scaled back its forecasts for Brent crude prices for 2012 from $130 to $120 a barrel, saying that economic headwinds in Europe will hit demand. Brent crude is currently down 1.65% at $100.03, just three cents away from the psychologically important $100 level. FTSE 100 - RisersTesco (TSCO) 378.20p +2.08%Morrison (Wm) Supermarkets (MRW) 288.20p +0.45%FTSE 100 - FallersVedanta Resources (VED) 923.50p -8.56%Weir Group (WEIR) 1,358.00p -8.18%Prudential (PRU) 499.10p -8.00%GKN (GKN) 155.20p -7.62%Fresnillo (FRES) 1,486.00p -7.36%Barclays (BARC) 144.90p -7.26%Xstrata (XTA) 734.00p -7.19%Lloyds Banking Group (LLOY) 31.12p -6.96%IMI (IMI) 638.50p -6.86%Legal & General Group (LGEN) 89.05p -6.75%NR