Congress President Rahul Gandhi on Thursday accused Prime Minister Narendra Modi of letting down farmers in Karnataka and gave him 'F' Grade in a report card, saying there was no contribution from the Centre to the state's farm loan waiver.Gandhi said that the Prime Minister's crop insurance scheme had made the "farmers suffer" while filling the coffers of the private insurance companies which have made "huge profits".He tweeted that the Congress will, in the next five years, create a unique "Agricultural Corridor" for 10 agro climatic zones in the state to develop sustainable agri businesses.The Congress chief said the farmers did not receive price of crops at 50 per cent above the Minimum Support Price (MSP)."Contribution to Congress state governments 8,500 crore Farm Loan waiver 0 Rs."PM's crop insurance scheme: Farmers suffer; (private) insurance companies make huge profits."No MSP+50%, for Karnataka farmers. Grade F,"He said the Congress government in the state had launched several schemes that has helped farmers."Anna Bhagya, Ksheera Dhare, Krishi Yantra Dhare, Surya Raitha and Loan waivers improved the lives of Karnataka's farmers. In the next 5 years, INC will create a unique 'Agricultural Corridor' for 10 agro climatic zones to develop sustainable agri businesses," he said.The attack came ahead of polling for the 224-member Karnataka Assembly, to be held on May 12. The results will be declared on May 15.