Agricultural Export Revitalization Act of 1990 - Amends the Merchant Marine Act of 1936 to extend the requirement that the Secretary of Transportation take steps to preserve the percentage share of certain commodities of waterborne cargoes exported from Great Lakes ports under the Agricultural Trade Development and Assistance Act of 1954. Phases out, over three years beginning in 1991, the requirement that 25 percent of the gross tonnage of certain U.S. exports be transported on U.S.-flag commercial vessels.

Requires the Secretary of State to initiate discussions with Canada to reduce or eliminate all tolls on the International Great Lakes and the Saint Lawrence Seaway. Requires the Secretary of Transportation to report to the appropriate congressional committees on the progress of such discussions.