Identifying canola varieties for dual-purpose use

Canola has recently shown significant potential as a dual-purpose crop in the high rainfall areas of southern NSW/ACT, Australia. Further development of the concept in other environments will require identification of suitable germplasm. We screened a broad range of current varieties and elite germplasm in contrasting environments (Canberra ACT, Wagga Wagga NSW, Naracoorte SA) in 2007 to identify the most appropriate phenological types which combined good early biomass production, high blackleg resistance and grain yield not significantly reduced by winter defoliation. A range of 36 entries was sown on three sowing dates at each site and plots were defoliated mechanically (~10 cm) to simulate heavy sheep grazing in mid-winter. Hybrid varieties produced up to 50% more early biomass (6-8 leaf stage when grazing would likely commence) than conventional varieties and triazine tolerant varieties 50 % less. Blackleg severity was increased by defoliation but this was minimised in varieties with good genetic resistance (Australian Blackleg Rating >7.5). Yield loss associated with defoliation was minimal if the terminal buds were not removed in the defoliation process (i.e. elongated < 15 cm) but significant loss (up to 60%) could occur if plants were defoliated at later stages depending on seasonal conditions. At all sites, canola varieties were identified which could be sown early, have 2-4 t/ha of biomass removed in mid-winter, and recover with no yield loss compared to grain-only crops sown at the recommended time. The study has identified varieties which combine suitable phenology with other desirable dual-purpose traits for further evaluation in different regions.