A Chinese customs document dated March 1 revoked the registration of Winnipeg-based agricultural handler Richardson International to ship canola seeds to China. That means the company is forbidden to export canola seeds to the country. Canada exported more than US$ 5 billion worth of canola last year and, according to the Canadian Canola Growers Association, almost half of it or  around five million metric tonnes worth, was destined for the Chinese market. Richardson International is the biggest supplier accounting for half the exports.