THE genetically modified Roundup Ready was the best-performing canola in independent trials run across Victoria this season.

In the National Variety Trial program, a plot of hyola502RR at Hamilton yielded 3.38 tonnes/ha - about 41 per cent higher than the average of all canola varieties grown at the site.

But in other trial sites in Victoria, hyola502RR did not perform as well.

According to a National Variety Trial report, the variability of varieties within and across herbicide-tolerance groups reinforced the need for more trials across regions and years to make robust performance predictions.

The Grains Research and Development Corporation's gene discovery manager, Juan Juttner, said that the limited data collected made it difficult to draw firm conclusions on varietal performance.

"There is an inherent level of variability in the results of variety trials across locations and year, so you need multiple trials across a number of years to confidently predict variety performance," Dr Juttner said.

There were 150 canola plots in Australia last season, 15 of which were of GM varieties across Victoria, NSW and Western Australia.

In Victoria, the trial sites were established in the Horsham, Hamilton, Teesdale and Shepparton districts.

National results show that triazine-tolerant canola varieties yielded lower than the imidazolinone-tolerant and Roundup Ready varieties.

"The difference between RR (Roundup Ready) and Imi (imidazolinone) groups was less pronounced," the NVT report said.

This was only the second year of results for GM canola.

More is expected to be planted in Western Australia, with the State Government lifting its moratorium on commercial plantings.

Dr Juttner said the NVT GM canola trials were designed to allow a comparison of yield within and across herbicide-tolerance groups, not the efficacy of each herbicide system.

"GM canola is one more piece of technology available for grain growers to consider, and the NVT results provide one of a number of data sources to draw upon to help make decisions regarding its potential use," he said.

The canola trial results and national report can be viewed at the National Variety Trials website.