July 9, 2003

After reports of some new crop varieties suffering yield losses when treated with selective herbicides, the Grains Research & Development Corporation (GRDC) has supported renewed testing for selective herbicide resistance tolerance within crop breeding programs.

Western Australian graingrowers have typically loaded a new wheat variety into their arsenal every four seasons, but as private breeding companies and consolidated public breeding efforts have cranked up, so has the wheat variety production line.

Besides wheat, other cereals and pulse and oilseed varieties have also poured into the market, largely underpinned by the GRDC’s investment in ‘Winter Cereal Improvement’ and ‘Crop Improvement’, which in 2002/03 were worth a combined $45 million.

However, driven by different goals, breeders of these new varieties have gone in numerous directions, venturing progressively further from traditional crop archetypes and, along the way, opening the door for new crops to develop susceptibility to selective herbicide treatments that could be applied to older varieties without diminishing yield.

This threatens to slug growers with the double-blow of paying $50 plus per kilogram for selective herbicide and the potential financial loss of inhibiting early plant growth.

Supported by growers and the Federal Government through the GRDC, Harmohinder Dhammu of the Department of Agriculture aims to identify genetic susceptibility to traditionally benign herbicides among new crop varieties before they are released.

Such sensitivities have previously been found in new pea, lupin and wheat varieties.

Mr Dhammu ran tolerance trials on wheat at Merredin, Mullewa, Newdegate and Esperance, barley at Katanning, peas at Mullewa and lupins at Mullewa and Wongan Hills, to identify resistance levels.

Among early results, he has identified metribuzin susceptibility in lupins, which Dr Mark Sweetingham is addressing in a separate GRDC project.

Trials also tested optimum application times for phenoxy herbicides on six wheat and six barley varieties to produce an accurate user guide.