It shall be presumed, for the purposes of this part, that all wine removed from a winery or wine cellar bonded under the internal revenue laws of the United States on payment of the internal revenue tax by a wine grower has been sold in this State by the wine grower, unless it is proved to the satisfaction of the board, in reports on forms prescribed by the board, that the wine has been exported from this State or sold for export by the wine grower making the report and actually exported from this State or that the wine is otherwise exempt from taxation under this part.