Mr Iwaniw had intended to retire on July 1 but stayed on to drive the approval of the proposed scheme of arrangement between ABB and Viterra.

Mr Iwaniw said that with the scheme book now close to completion, it was an appropriate time to move on.

"ABB Grain is a solid franchise with a great future," he said.

"I wish the board and the management team every success.

"I also thank all my colleagues at ABB Grain for their tremendous support and commitment over the years. They are what makes this company special and I truly appreciate their outstanding efforts."

Company chairman Perry Gunner thanked Mr Iwaniw for his loyalty and his efforts over a long career and, in particular, for continuing to act as managing director after his contractual term had expired to progress the proposed Scheme of Arrangement with Viterra.

"Michael has played a significant role in the growth of ABB and the Australian grains industry," Mr Gunner said.

"He was instrumental in taking ABB from a statutory marketing authority to an ASX-100 corporation.

"His performance in building strong trade relationships with grain buyers in the Middle East and Japan fostered an ongoing point of supply for ABB Grain grower customers across south eastern Australia.

"Michael was also instrumental in developing a world-class trading group across a range of commodities for the benefit of employees, shareholders and growers."