Thermal time and vernal time response of commercial and pre-release Canola cultivars

Mrs Danielle Malcolm1, Rohan Brill2, Hongtao Xing3,4

1NSW DPI , Wagga Wagga, Australia

2Brill Ag, Ganmain, Australia,

3NSW Department of Primary Industries

4Wagga Wagga Agricultural Institute


Trials were conducted at Wagga Wagga in 2018, 2019 and 2020 with commercial and pre-release canola cultivars sown in late March and late April, to investigate the phenology differences between varieties.

Contrasting seasons were experienced across the experimental period, with differences in varietal response to thermal and vernal time observed  Vernal time was accumulated quicker in 2020 (relative to thermal time) than the previous two years but thermal time was accumulated at a slower rate. This meant that certain varieties did not need as much thermal time to reach flowering.

In 2020 both fast and slow developing cultivars responded to the high proportion of vernalising temperatures by releasing the ‘handbrake’ on their vernal response, reducing the amount of thermal time required to switch from the vegetative growth stage to the reproductive growth stage. From the early sowing date, varieties flowered earlier than in previous years. The fast-mid cultivar 44Y90 (CL) flowered a month earlier in 2020 than 2019. The slow developing cultivars 45Y91 (CL) and ATR Wahoo flowered 17 and 13 days earlier. Nuseed Diamond, considered a spring cultivar with little to no vernalisation response, flowered 21 days earlier in 2020 than 2019 despite 2020 being a cooler season.

The results observed for the mid and slow developing cultivars were all able to be explained by the temperature differences across season, however the fast development of the spring cultivar Nuseed Diamond in 2020 is more difficult to explain and may indicate that there are other mechanisms at play.


Danielle has been working in Canola Agronomy team at DPI since 2016 with involvement in various experiments. Danielle has managed the phenology trials at Wagga with commercial and pre-released cultivars. Danielle has also been involved in the Optimized Canola Profitability project and High Yielding Canola project and more recently is involved with the Frost tolerance project in Wagga and a project looking at improving production of grower retained Open Pollinated canola seed.



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