Asia's response to tightening global grain supplies has aggravated food price inflation and uncertainty, according to an Asian Development Bank (ADB) report released here on Friday. Export bans and price floors imposed by grain exporters including China, Pakistan, Vietnam and India have increased price volatility and uncertainty in the international rice Markets reducing supplies. "These have been contributing significantly to the surge in rice price especially since the end of 2007,' a Manila-based lender said.