MF Global exit undermines Australia grains futures * MF Global collapse sidelines Australian grain futures * Only 130 ASX grain contracts traded on Wednesday vs average daily volume of 1,800 * Liquidity key to success of Australian ag futures market * Major players needed to fill hole left by MF Global's demise http://www.reuters.com/article/2011/11/03/australia-grains-mfglobal-idUSL4E7M301220111103