The Canadian Wheat Board, the world's biggest seller of the grain, has for a second successive month cut estimates for growers' returns, blaming weak market conditions.

The Winnipeg-based group cut by up to Can$28 per tonne its forecast for returns on its 2009-10 wheat pools, with the estimate for most durum pools cut by Can$31 per tonne.

The downgrade, coupled with July's revisions, has put growers of feed wheat and the lowest class of durum, the type used in making pasta, on course to receive up to 21% less for their grain than looked likely five weeks ago.

"The wheat market has been pressured by the ongoing harvest in the northern hemisphere and by generally favourable growing conditions," the CWB said.

Quality issue

Durum had been hurt by higher North American production estimates and the completion of the harvest in Mediterranean countries.

"European crop quality has been mixed, with rains causing problems with Italian quality. However, France, Spain and Greece are reporting mostly good quality."

The board added that the quality of the North American harvest, which less than 5% complete, would play "a large role in determining price movement during the next year".

The CWB announcement came shortly after AWB, Australia's former wheat export monopoly, closed its offer of a Aus$15-a-tonne premium to farmers who committed grain ahead to its pools.

"Wheat grower support for AWB's early commitment premium pool contracts has been so strong that available tonnage has been fully contracted and the offer has now closed, a week ahead of schedule," the group said.